Module Overview
Purpose of this module The purpose of this coaching module is to provide you with a brief background to the requirements of the Gas Testing procedure and the Confined Space Entry procedure. Provide the necessary understanding of the basics of hazard management of oxygen enriched / deficient, toxic and flammable gas atmospheres. Enhance your competency and ability to identify hazardous atmospheres and environments that may be Immediately Dangerous to Life and Health and determine the associated risks in the work place during pre-work site inspections. Understand the relevance of this and its application as required by the Gas Testing procedure PR1154, the Confines Space Entry procedure PR1148, Gas freeing, purging and leak testing  procedure PR 1073, the H2S procedure PR1078 and the PTW system PR1172. 
Learning outcomes and objectives    The aim of this module is to provide you with the necessary information and activities to enable you to:   
Develop effective understanding of Gas testing by: 
  Understanding the narcotic effects of hydrocarbons.Effective use of atmosphere / gas measuring and monitoring equipment.Gas testing in confined spaces, Gas testing for hot work.Interpreting and documenting the results of a gas test, 
  Assessment criteria     To demonstrate achievement of the Learning Objectives of this module you are required to meet the criteria and/or provide the following evidence:   When given the names of three different hydrocarbons, correctly explain their narcotic effects.Correctly explain:The hazards of operations within an oxygen deficient, toxic or flammable environment;What the confined space criteria are;The behaviour of different flammable and toxic gases including H2S, SO2, CO, CO2, and alkanes that are normally vapour at ambient conditions; The operating principles of atmosphere monitoring and measuring equipment; The pre-start – correctly explain How you would correctly calibrate atmosphere monitoring and measuring equipment;How to set up the relevant detector for each gas testing application;The range and frequency of tests – correctly explain:How a representative atmosphere sample should be obtained; How to specify continuous monitoring or retesting frequency; Given an operational scenario, where you would site sentinel monitoring equipment; What ‘hot work’ means and zone classifications;The hazards associated with  it in relation to the production of flammable and toxic gases;The hazards and properties of flammable gases;The principles of hot work gas testing;At an actual or simulated operational workplace for confined space entry and hot work:Carry out a suitable and sufficient risk assessment after interpreting operational requirements.Demonstrate you can correctly identify the appropriate safe systems of work needed and can use them, including the Permit to Work system Demonstrate you can select and use the correct PPE and RPE before a gas testing operation.Demonstrate you can carry out gas detector pre-start checks correctly. Demonstrate you can perform gas tests in the correct sequence.Given a set of readings from the instruments you selected, demonstrate you are able to correctly interpret and document the results. 
Managing Health and Safety at a Corporate level   Any reputable organisation manages Health and Safety by the imposition of the requirements of an HSE management system on its employees and partners or stakeholders eg contractors etc. PDO is no exception. These management systems comprise primarily of;            Policies, Rules, Regulations, (i.e. statutory requirements), Standards, Practices, Procedures                          Specifications, Guidelines and Codes of practice. The above essentially forms the “system of work” which enables individuals to be guided in the correct manner regards the execution of any task or process management. The PDO HSE Management System as defined in CP 122 is structured as follows: This is an extract from the PDO HSE Code of Practice : EMPLOYEES, SUPPLIERS, CONTRACTORS, AND SUB-CONTRACTORS All PDO employees, suppliers, contractors, and sub-contractors shall be responsible and accountable for following the instructions of their line leader / supervisor, in accordance with PDOs HSE Policy and other requirements of PDO’s HSE Management System. Therefore, the requirements of the System must be known.   
Authorised Gas Tester: An Authorised Gas Tester (AGT) is a person who has passed the Gas Testing Course and holds a current Gas Testers Card, and has passed either a Permit to Work Signatories or Holders Course. 
 Confined Space: Has limited or restricted means of entry or exit Is large enough for an employee to enter and perform assigned work, and Is not designed for continuous occupancy by the employee. 
Overview of Hazard Identification
Introduction All Hazardous gas exposures within PDO operations need to be carefully identified and evaluated for potential health and safety exposures through a risk assessment and analysis process.  There are several standards and assessment techniques to identify hazards. Examples of these process would include amongst others FMECA (Failure Modes and Effects Criticality Analysis) HAZOPS (Hazard Operability Studies) and HAZID (Hazard Identification) which can be used to establish a list of Hazards to be considered in any risk assessment process or review.  It is important that the process is inclusive of all the significant hazards with a potential fatality consequence and not just the common hazards that are well known and understood. This will include all probable cases where there is the potential for exposure to toxic, flammable gases or life threatening atmospheres.  Employers in the PDO community have to ensure that a systematic and thorough examination of the work place is undertaken and the prevailing conditions and practices are identified, recorded and the significant findings evaluated to determine their risk potential. Furthermore, all contractors working for PDO are obliged in terms of PR1171 part II to identify hazards and manage associated risks.
PR 1171 part IISection 2.6.2 Contract-Specific HSE Management Plan Contractor(s) shall, following the Contract Award, kick-off Meeting and on site HSE Workshop, revise its original HEMP and from that develop the Contract-Specific HSE Management Plan.  Contractor(s) shall describe how the HSE Management Plan will apply its established, generic programs to manage its activities in the specific contract. Note:
Contractor(s) shall identify the contract-specific work activities it will perform and the anticipated HSE hazards associated with the work.  Contractor(s) shall clearly describe its plan (controls) for minimizing the potential effects of these anticipated hazards. 
Activity 1 What is Gas?        
Gas    Note
  Gas is one of the four classical states of matter; the others being; liquid, solid & plasma.
At near absolute zero, a substance exists as a solid. This is the lowest temperature that is theoretically possible, at which the motion of particles that constitutes heat would be minimal. It is “zero” on the Kelvin scale, equivalent to        –273.15°C or – 459.67°F. As heat is added to a substance it melts into a liquid; at its melting point, boils into a gas; at its boiling point, and if heated high enough would enter a plasma state; in which the electrons are so energized that they leave their parent atoms from within the gas.
Solid, Liquid and Gas
Activity 2 Define the properties of gas  
Properties of GasA gas has no definite shape or volume of its own.       It acquires the shape of the container.       Reason: Intermolecular attraction is the weakest in gases whereas intermolecular separation is the largest. Hence, molecules in a gas move very fast and the gas expands to fill all the space       available. 2. A gas has no surface of its own.       Reason: Molecules escape from an open container and disperse in air randomly 3. A gas is not rigid and is easily compressed.       Reason: Intermolecular separation is very large in gaseous state, which can be decreased by applying pressure. 4. A gas can diffuse into another gas.       Reason: Molecules in a gas move very fast. Hence the rate of diffusion is very large. 5. A gas on cooling changes into liquid state.       Reason: Cooling reduces intermolecular separation and increase intermolecular force of attraction. A gas can flow in all directions. It requires a vessel closed from all sides to contain it
Source of Natural GasNatural gas is a made up of a mixture of hydrocarbons. The main hydrocarbon in natural gas is methane, but there are also small amounts of ethane, propane and butane. Natural gas originates from organic matter like plants and tiny sea creatures that lived millions of years ago. As the organic matter decayed it was covered with layers of silt and clay which over time turned into rock. Over millions of years, the heat of the earth and the pressure from the weight of rocks above transformed some of the organic matter into the fossil fuels coal, oil and natural gas. The movement of water, and pressures within the earth’s crust, caused the oil and natural gas to move. Some of the oil and gas accumulated in traps or reservoirs (formed by porous rocks, covered by non-porous rocks) within the earth’s crust.
Radon Gas
Activity 3 Discuss the typical hazards associated with gas that are found in oil and gas exploration and production?    

What is a hydrocarbon?
Hydrocarbons are the simplest organic compounds. Containing only carbon and hydrogen atoms, they can be straight-chain, branched chain, or cyclic molecules. Carbon tends to form four bonds in a tetrahedral geometry.
Hydrocarbons and alkanes  Hydrocarbons Most of the compounds in crude oil are hydrocarbons. This means that they only contain hydrogen and carbon atoms, joined together by chemical bonds. There are different types of hydrocarbon, but most of the ones in crude oil are alkanes. Alkanes The alkanes are a family of hydrocarbons that share the same general formula. This is: CnH2n + 2 The general formula means that the number of hydrogen atoms in an alkane is double the number of carbon atoms, plus two. For example, methane is CH4 and ethane is C2H6. Alkane molecules can be represented by displayed formulae in which each atom is shown as its symbol (C or H) and the chemical bonds between them by a straight line. Structure of alkanes alkane formula chemical structure ball-and-stick model methane CH4 ethane C2H6 propane C3H8 butane C4H10   Notice that the molecular models on the right show that the bonds are not really at 90º. Alkanes are saturated hydrocarbons.   This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air, which we call burning or combustion.  
Activity 4 Define the narcotic effects of hydrocarbons  
Narcotic effects
DoseThe severity of effects of an inhaled toxin on a body depends on: Concentration of toxin (ppm) in airDuration of exposure (number of breaths)
What gases should we be concerned about in the oil and gas business?
Activity 5 What gases should we be concerned about in the oil and gas business? Write their names and symbols  
 H2S and SO2                           Hydrogen Sulphide and Sulphur Dioxide –                           Under certain conditions toxic gases may be found in the atmosphere.   CH4                    Methane                           Explosive gas found underground and in Oil and gas process facilities (Hydrocarbon atom)     O2                      Oxygen                           Before entering any confined space ensure the atmosphere is breathable i.e. it can sustain human life.   CO2 & CO           Carbon dioxide and Carbon Monoxide   N 2                      Nitrogen  
When should gas tests be conducted?1.       Before work starts and 2.       During continuous work where there is the potential for exposure to a gas leak Gas testing is mandatory prior to work being undertaken in a process or hydrocarbon area that carries a risk to personnel or equipment from exposure to explosive, flammable, toxic or life threatening vapours. Gas testing shall also be required in any other area where the above risks are considered to exist which are covered by the PDO Permit to Work (PR1172) or a 3rd Party compliant system.
Why do we need to test for gas?To ensure there are no toxic gases present in the work area and in the air and that the atmosphere is breathableTo ensure the oxygen levels in the air are sufficient to support lifeTo ensure there are no flammable or explosive gases present and so minimise the possibility of an explosion happening. 
How does the human breathe? 
Activity 6 Types of atmosphereList the five recognised types of atmosphere There are five recognised types of atmosphere: Oxygen enriched or depleted (deficient)Toxic Flammable / combustible or explosive Nitrogen enrichedHydrocarbon enriched
Oxygen Enriched Atmosphere  At atmospheric level the normal atmospheric concentration of oxygen is 20.8% vol. Atmospheres containing more than 21.5 % vol. oxygen shall be treated as oxygen enriched or hyperoxic. Generally, oxygen enrichment does not occur often, as the source of the extra oxygen shall have to be introduced. Oxygen enriched atmospheres when mixed with hydrocarbons can result in explosive mixtures quicker than would be the case with normal air (20.8%). Oxygen enrichment will significantly increase flammability of clothing, grease and other combustible materials. Oxygen enrichment can result from: Leaks from oxygen containing equipment such as gas cylinders, valves, hoses and welding torches;Inadvertent use of oxygen instead of air for ventilation or breathing air;Deliberate addition of oxygen to increase the level of an oxygen deficient atmosphere. Any increase in the oxygen level above normal during confined space entry activities shall be investigated, a Risk Assessment completed and appropriate measures taken.   The most common oxygen containing equipment is that used in gas cutting operations. Cylinders, gas hoses, valves and welding torches shall be handled with care and should be daily inspected for damage. Gas cylinders shall not be taken into confined spaces unless the risks have been assessed and appropriate authorisation is obtained from the Responsible Supervisor. If allowed into the confined space all such equipment shall be removed during breaks and at the end of the working day. All O2 cylinder valves shall be closed when not in use.   
Oxygen Depleted (deficient) AtmosphereAtmospheres containing less that 20% vol. oxygen shall be treated as oxygen depleted (deficient) or hypoxic. Such atmospheres can occur when gas freeing or purging has been carried out to remove hydrocarbons / toxics or air. The oxygen in the atmosphere shall have been normally replaced / diluted with an inert gas i.e. nitrogen. Oxygen deficiency in an atmosphere can result in asphyxiation. A relatively small reduction in the oxygen level can lead to impaired mental ability and can provoke a feeling of euphoria or wellbeing leading to an overoptimistic judgment of the situation. The effects generally occur without alerting the senses. Loss of consciousness can occur without warning. This can happen even in circumstances where only a person’s head is inside a confined space. Very low oxygen concentrations, below 10%, can lead to unconsciousness and death. Inhaling an atmosphere with no oxygen results in instant death. There is no panic or discomfort; death is swift and silent.   Oxygen deficiency can result from: Displacement of air from low points in a confined space by heavier gases such as hydrocarbons or carbon dioxide;Purging of the confined space with an inert gas to remove flammable or toxic gases, fumes, vapours or aerosols;Naturally occurring biological processes that consume oxygen, which can occur in sewers, storage tanks, wells etc.;Leaving a vessel completely closed for some time, since the process of rust[1] formation on the inside surface consumes oxygen;Increased levels of carbon dioxide evolving from limestone chippings associated with drainage operations;Burning and welding, which consume oxygen;Displacement of air during pipe freezing with liquid nitrogen;Gradual depletion of oxygen as workers breathe in confined spaces and where provision of replacement air is inadequate.   Any reduction in the oxygen level from the atmospheric concentration shall be accounted for or investigated, the risks assessed and appropriate measures taken.   Entry into confined spaces containing 16% to 20% by volume oxygen shall not be allowed unless a Risk Assessment has been completed and approval has been obtained from the appropriate authority. The wearing of Breathing apparatus is mandatory when entering this type of atmosphere. 

Toxic Atmosphere  
Toxic atmospheres are those that contain concentrations of vapours that shall cause injury or death to humans. Such atmospheres may have sufficient oxygen to support life and insufficient flammable concentrations to cause explosions or fire, but may contain sufficient concentrations of the toxic to harm personnel. An example would be H2S or mercury. Toxic atmospheres are formed when:                Toxic or poisonous substances combine with air or other gases or vapours In enclosed or confined spacesIn clouds, layers of gas or vapourIn sufficient concentrations to be harmful or fatal to humans 
Flammable or Explosive Atmosphere  Flammable or explosive atmospheres are those that contain gas/air mixtures that when exposed to an ignition source will or may ignite and burn. Such atmospheres can be created when opening pipework or equipment that contains or has contained hydrocarbons. This is known as breaking containment. Flammable atmospheres are formed when gas and air mixtures accumulate between upper and lower flammable limits. They are ignited by contact with flames, heat, sparks, static electricity or at self-ignition temperatures. 
Flammable gas testingGas testing shall be carried out to detect accumulations of flammable vapours, fumes or dust in atmospheres which could ignite in the presence of a source of ignition. Flammable vapours or fumes typically result from: Materials previously processed or stored in the vessel or tank;Sludge or other deposits disturbed during cleaning;Material left under scale, even after cleaning;Material leaking through the tank floors;Material leaking from behind vessel linings (lagging, refractory etc.) or from vessel fittings such as tank floating roof pontoons and legs, instrument connections or pipes;Materials leaking from flanges or vents on process pipes running through the confined space, e.g. process tubes in a furnace combustion chamber;Vapour entering the confined space from nearby process plant that has not been effectively isolated or from nearby work that is not well controlled;Solvents brought into the space for cleaning, painting, dye penetration tests or in adhesives;Gases brought into the space / area for welding or gas cutting, including leakage from cylinders, valves and hoses; Contaminated firewater / process water used to wash the confined space and introduced by hoses; Vapour or fumes that build up in sewers, manholes, contaminated ground or excavations.   A source of ignition can be any heat source having enough energy to ignite a flammable vapour air mixture, or to raise the temperature above the auto-ignition temperature. Possible ignition sources include:   Open flames and sparks resulting from welding, gas cutting and grinding;Sparks or arcs produced by electrical equipment, lightning and electrostatic charges;Hot pipes or exhausts that can raise the flammable mixture above the auto-ignition temperature;Heat of friction during drilling, sawing or other cutting activities;Pyrophoric materials, e.g. iron sulphide in scale;Thermite reactions from aluminium or other alloy tools striking against rusted iron or steel;Any highly reactive material capable of producing sufficient heat for combustion, for example: –     Strong oxidising substances, such as hydrogen peroxide used in waste treatment facilities; –     Chemicals that undergo self-accelerating exothermic reactions when a critical temperature is reached, such as ethylene oxide.  
The recommended approach to controlling flammable vapours in confined spaces or where ‘hot work’ is being undertaken is to eliminate all flammable materials from area before the work is undertaken. The objective should be no detectable flammable vapour, i.e. an explosimeter reading less than 1% LEL.
Toxic gas testingToxic gas testing shall be carried out to identify and detect toxic substances either in or adjacent to the confined spaces or other places of work. Substances can be solids, liquids or gases. Toxic vapours can cause injury, acute or long-latency illness, or death, depending on the characteristics of the substances, the concentration and the duration of exposure. For example, prolonged exposure to benzene can cause kidney damage or even leukaemia. Toxic hazards in confined spaces can result from the same sources as the flammable hazards. Common toxic substances in the oil and gas industry are: Acute toxic gases such as hydrogen sulphide, carbon monoxide, hydrogen fluoride, ammonia and chlorine; Hazardous liquids such as benzene, polycyclic aromatics, lead/anti-knock compounds, hydrazine and biocides; Narcotic gases and vapours such as butane, pentane, hexane, gasoline and gas condensate; Toxicity data for specific substances, e.g. Material Safety Data Sheets (MSDS) or Safe Handling Of Chemical Cards (SHOC), shall be required from the supplier of materials or from government authorities, and shall be made available on site. If these are not available then a competent industrial hygienist shall assess the toxicity of the intermediates and products. Crude oil and refinery process streams are mixtures of many hydrocarbons that individually have significant toxic or narcotic effects. The Health Risk Assessment (HRA), as input to the Job Hazard Analysis (JHA), shall assess the hazards of the mixture in the situation / areas where persons could be exposed. Specifically, the HRA should make a recommendation on whether flammability measurements are sufficient to detect harmful levels of the potentially toxic substance. Different criteria may be needed for: Confirming that the atmosphere in the confined space is safe for entry, for planned work, andRequiring persons to leave the space in case of an increased level during the work Substances that are harmful by inhalation normally have an assigned Occupational Exposure Limit (OEL). An Action Limit of 50% of the published OEL shall be applied as the trigger for implementing specific measures for controlling exposure to the toxic substance during the confined space work, but the target should be to reduce the airborne concentration to ALARP. OEL data may not be available for some toxic dusts, sludge and other substances, in which case specialist occupational hygiene advice should be sought. Entry into confined spaces containing a concentration of toxic vapour, fume or dust between the OEL and the IDLH value shall be allowed only by exception when and it is not practical to ventilate the confined space or otherwise remove the hazard to reduce the toxic concentration. In this case it shall only be allowed when the source, nature and concentration of the toxic hazard is understood and exposure is adequately controlled by other means. Entry into confined spaces containing a concentration of toxic vapour, fume or dust above the IDLH value shall not be allowed. The most notable toxic gas encountered in PDO operations is hydrogen sulphide (H2S). Allowable concentrations are related to the Threshold Limit Value (TLV) which represents the concentration to which a worker may be exposed without suffering adverse health effects.   Interim Amendment 1078_0512_01 refers – PR 1078 May 2012 For the H2S the TLV is lowered from 10 ppm to 5 ppm, for an 8-hour period. However the set point alarm of the personal H2S detector remains at 10ppm. The short-term exposure level (STEL) for H2S is 10 ppm and is the concentration of H2S gas in air above which protective equipment must be used. –  (refer – PR1154 page 34 and PR 1078)   

Hydrocarbon Enriched Atmosphere  
Hydrocarbon enriched atmospheres are those where the presence and concentrations of hydrocarbon vapours are sufficient to induce a narcotic effect on personnel breathing without protection inside the atmosphere. 

Effects of oxygen deficiency
21%        Normal breathing 17%        Candle will not burn 12-16%   Breathing laboured, increased heart rate, difficulty in attention and coordination 11-14%   Unable to think, no perception of danger, impaired self-rescue, fatigue, loss of                hearing 8-11%     Nausea, vomiting, unable to stand, person is dying, but doesn’t know or care 6-8%       Loss of consciousness, heart stops, possible to resuscitate if immediate attention 0-6%       Immediate coma, respiratory arrest, death
Hazardous area classification  Zone 0: An area in which an explosive gas atmosphere is present continuously or for long periods; Zone 1: An area in which an explosive gas atmosphere is likely to occur during normal operation; Zone 2: An area in which an explosive gas atmosphere is not likely to occur under normal operations and, if it occurs, will only exist for a short period of time.              
Methane UEL  –  LEL

Explosive limit
All combustible gases and vapours have an “explosive limit” between which the gas or vapour, mixed with air, is capable of sustaining the spread of flame. These can be referred to as the explosive or flammable range or limit

The upper explosive limit UEL
The upper explosive limit (UEL) refers to the highest concentration of gas in the atmosphere which results in a combustible mixture. The UEL for H2S is 46% This means that if there is more than 46% by volume of H2S in air, the mixture is too rich to support combustion. How may ppm is this?
The lower explosive limit LELThe lower explosive limit (LEL) refers to the lowest concentration of gas in the atmosphere which results in a combustible mixture. The LEL for H2S is 4.3%. 1% of H2S by volume represents 10,000 ppm. This means that if there is less than 4.3% by volume of H2S in air the mixture is too lean to support combustion. When gas test equipment indicates 100% lel there is 4.3% by volume of H2S in the test atmosphere. For most practical gas testing purposes, it is the LEL, which is significant. The AGT is responsible for recording the percentage of LEL for the specific flammable gas being tested on the permit
 Text Box: % by volume For most practical gas testing purposes it is the LEL which is significant. 100% of LEL for Methane means 5% by volume. 50% of LEL for Methane means 2.5% by volume The AGT is responsible for recording the percentage of LEL for the specific flammable gas being tested on the permit.
Activity 7 How many parts per million is 1% of H2S by volume?What is the LEL of H2S and how many parts per million is this?How many parts ppm of H2S are there in 25% lel?How many parts ppm of H2S are there in 50% lel?How many parts ppm of H2S are there in 100% lel?  
Flash PointThe flash point of a volatile substance is …. “The lowest temperature at which it can vaporize to form an ignitable mixture in air”.
Carbon Monoxide CO What is carbon monoxide?  Carbon monoxide is a colourless, odourless, and tasteless gas which is highly poisonous. The chemical formula for carbon monoxide is CO, one molecule of carbon and one molecule of oxygen. Under high pressure, it becomes a liquid. It is produced by the incomplete burning of natural gasgasoline, liquefied petroleum gas, oildiesel fuel, kerosene, coal, charcoal, or wood. It can be released from wildfires. Appliances that use these fuels may also produce carbon monoxide Running motor vehicle engines and tobacco smoke also produce carbon monoxide. Other sources of carbon monoxide include unvented kerosene and gas space heaters; leaking chimneys and furnaces; gas stoves; back-drafting from furnaces, gas water heaters, wood stoves, and fireplaces; and automobile exhaust, exhausts from industrial generators
How can carbon monoxide affect my health?Exposure to very high concentrations of carbon monoxide can cause convulsions, coma, and death through carbon monoxide poisoning. Exposure to high levels can cause impaired vision and coordination, unconsciousness, headaches, dizziness, confusion, vomiting, muscle weakness, and nausea If a person is pregnant, exposure to carbon monoxide may cause miscarriage or increase the risk of damage to a developing foetus; it may also result in babies with low birth weights and nervous system damage. Carbon monoxide poisoning can occur sooner in young children; pregnant women; elderly people; people with anaemia, lung disease, or heart disease; people at high altitudes; or people who smoke cigarettes. Exposure to low levels of carbon monoxide can cause fatigue, chest pain, shortness of breath, memory loss, skin lesions, sweating, and flu-like symptoms. In the long term, exposure to low levels can cause heart disease and damage to the nervous system. Skin contact with liquid carbon monoxide in the workplace can cause frostbite. Carbon monoxide poisoning is caused by inhaling combustion fumes. When there’s too much carbon monoxide in the air, your body replaces the oxygen in the haemoglobin of your red blood cells with carbon monoxide. This keeps life-sustaining oxygen from reaching your tissues and vital organs. The effects of CO exposure can vary greatly from person to person depending on age, overall health condition i.e. physiology of the individual subject and the concentration and length of exposure. Various appliances fuelled by wood or gas produce carbon monoxide, including: Car and truck enginesPortable generators FurnacesWater heatersCooking rangesCharcoal grillsFireplacesFuel-burning space heatersWood-burning stoves Normally the amount of carbon monoxide produced by these sources isn’t cause for concern. But if appliances aren’t kept in good working order or if they’re used in a closed or partially closed space — such as using a charcoal grill indoors or running your car in a closed garage — the carbon monoxide can build to dangerous levels. Smoke inhalation during a fire also can cause carbon monoxide poisoning Normally the amount of carbon monoxide produced by these sources isn’t cause for concern. But if appliances aren’t kept in good working order or if they’re used in a closed or partially closed space — such as using a charcoal grill indoors or running your car in a closed garage — the carbon monoxide can build to dangerous levels. Smoke inhalation during a fire also can cause carbon monoxide poisoning
Carbon Monoxide toxicities in parts per million (ppm):35 ppm maximum concentration for continuous exposure over 8 hour period tolerable time weighted average (TWA) 200 ppm ceiling concentration not to be exceeded 1200 ppm concentration immediately dangerous to life and health (IDLH)
Properties of Carbon MonoxideCO is slightly lighter than air, and is a by-product of iron smelting, during some processes in modern technology. The properties of Carbon Monoxide are: ColourlessOdourless – Cannot smell itFlammable
Carbon Dioxide CO2 What is carbon dioxide? Carbon dioxide is a colourless, odourless gas that has a faint acid taste. It can also be a liquefied compressed gas or white flakes or cubes. In solid form, it is used as dry ice. Carbon dioxide can be found naturally in spring water and is released when volcanoes erupt and trees are cut down. When people breathe, they exhale carbon dioxide. Carbon dioxide is also produced by burning fossil fuels, such as coal, oilgasolinenatural gas, and diesel fuel. The chemical formula for carbon dioxide is CO2

In the atmosphere, carbon dioxide is part of the global carbon cycle between the atmosphere, oceans, land, marine life, and mineral reservoirs. It is a “greenhouse gas” because it absorbs heat in the atmosphere, sending some of the absorbed heat back to the surface of the earth and contributing to global warming. Carbon dioxide emissions represent about 80 percent of all greenhouse gas emissions in the United States. Sources of carbon dioxide emissions, which contribute to climate change, include fossil fuel burning, electricity generation, transportation vehicles, cement or lime manufacturing, waste burning, and natural gas flaring
How can carbon dioxide affect my health?  Carbon dioxide in its gaseous form is an asphyxiant, which cuts off the oxygen supply for breathing, especially in confined spaces. Exposure to concentrations of 10 percent or more of carbon dioxide can cause death, unconsciousness, or convulsions. Exposure may damage a developing foetus. 
Exposure to lower concentrations of carbon dioxide can cause hyperventilation, vision damage, lung congestion, central nervous system injury, abrupt muscle contractions, elevated blood pressure, and shortness of breath. Exposure can also cause dizziness, headache, sweating, fatigue, numbness and tingling of extremities, memory loss, nausea, vomiting, depression, confusion, skin and eye burns, and ringing in the ears. 

If your skin touches dry ice, you can get frostbite or blisters. 
You may be more affected by exposure to carbon dioxide if you have a cardiac, lung, or blood disease or condition. 
Properties of Carbon dioxide (CO2):  Asphyxiate, displacing airNot flammable1.5  times heavier than airLiquid very cold causing skin burnsIrritant to eyes and respiratory tractTLV: 5,000 ppm (8 hrs. TWA)STEL: 30,000 ppm (15 minutes TWA)IDLH: 40,000 ppm
A vital ingredient

Sulphur Dioxide
What is sulphur dioxide? Sulphur dioxide is a colourless gas with a pungent and suffocating odour, similar to the smell from a struck match. It has an acidic taste and is a liquid when under pressure. Sulphur dioxide is formed when fuel containing sulphur, such as coal and oil, is burned. The chemical symbol for sulphur dioxide is SO2. 

Most sulphur dioxide in the air comes from the burning of coal and oil at electric power generation plants. Other sources of sulphur dioxide in the air are industrial facilities that use coal or oil, petroleum refineries, cement manufacturing, metal processing, paper pulp manufacturing, and copper smelting. Trains, large ships, and some diesel equipment burn high sulphur fuel, which releases sulphur dioxide into the air. It can also be released into the air by mother nature ie from volcanic eruptions.   
How can sulphur dioxide affect my health?Short-term exposure to high levels of sulphur dioxide in the air can be life-threatening by causing breathing difficulties and obstructing airways, especially for people with lung disease. Long-term exposure to persistent levels of sulphur dioxide can cause chronic bronchitis, emphysema, and respiratory illness. It can also aggravate existing heart disease. 
When sulphur dioxide reacts with other chemicals in the air to form tiny sulphate particles, these particles can gather in the lungs and cause increased respiratory problems and difficulty breathing. Long-term exposure to sulphate particles can cause respiratory disease and even premature death. Prolonged industrial exposure to sulphur dioxide may decrease fertility in men and women. 
Breathing sulphur dioxide can irritate the nose, throat, and lungs, and cause coughing and shortness of breath. Short-term exposure to sulphur dioxide can cause stomach pain, menstrual disorders, and watery eyes, inhibition of thyroid function, loss of smell, headache, nausea, vomiting, fever, convulsions, and dizziness. 
At work, direct contact with sulphur dioxide as a gas can irritate and burn the skin and eyes, with possible eye damage. Direct contact with sulphur dioxide as a liquid can cause frostbite.
Properties of  Sulphur dioxide SO2  Not combustibleColourlessStrong Odour of burnt matchesHeavier than AirLow level alarm 2 ppmHigh level alarm 5 ppmPrecaution if SO2 is detected leave the area immediately
Hydrogen Sulphide Hydrogen Sulphide (H2S) is an extremely dangerous substance and can cause fatalities if not managed correctly. H2S can be present in the gas and liquid streams within the PDO operations. H2S in the upstream oil and gas industry comes from: the original reservoir, as a result of the hydrocarbon source material and the conditions under which it was converted to oil and gas. If this is the case then H2S will be produced with the fluidsthe reservoir after prolonged injection of water with oxygen (brackish or formation water) which may result in ‘souring’ of the fluids within it due to the action of sulphate reducing bacteria (SRB) introduced during the injection process. Any H2S will be subsequently produced with fluids.
Why are oil and gas fields a safety concern?    Oil and gas fields are areas where oil and natural gas have accumulated under the land’s surface. Oil and gas fields can also be offshore in lakes and oceans. Oil and gas exploration operations drill in these fields to extract oil and gas for sources of energy.   These operations pose many health, environmental, and safety concerns. Health concerns in oil and gas fields include air emissions of toxic chemicals, drilling waste, radioactive waste, and contaminated water produced by drilling operations. Oil and gas production can emit hazardous air pollutants, including benzenetoluene, and xylenes. These activities can emit carbon dioxide and methane, which are greenhouse gases that contribute to global warming and climate change. Operations at oil and gas fields can also emit nitrogen oxidesvolatile organic compounds[2]carbon monoxide, sulphur, and particulate matter.   Air emissions can come from several sources in oil and gas fields. Sources include equipment engines, drilling rigs, pump jacks, boilers, heaters, generators, combustion flares, storage tanks, injection pumps, dehydrators, vehicles, and oil and gas skimmers. One of the major sources of air emissions at gas fields are compressor stations that move natural gas through pipelines and gas processing plants.   Oil and gas field activities produce drilling waste, which contains drilling mud, shale, rock waste, and drilling fluids. Wastes include tank bottoms, which are liquids that collect in the bottom of storage tanks and other production equipment. Other wastes are fluids from treatment and stimulation activities, oily soil and dirty rags, sand, pit and sump waste, and waste from cleaning pipelines.   The underground rock and sediments that hold oil and gas deposits contain naturally occurring radioactive materials, (LSA or NORM) including radium, uranium, and thorium. Radium decays to produce radon, an invisible and odourless radioactive gas. Oil and gas production can leave behind radioactive waste that can settle inside pipes, sludge, equipment, evaporation ponds, waste water, and drilling mud.  During drilling, a mixture of oil, gas, and underground formation water is pumped to the surface. When the water is separated from the oil and gas, it is called produced water. Produced water can contain salt, oil, grease, chemicals used in drilling, and naturally occurring radioactive material. It is the largest volume waste from oil and gas production. Produced water in the past was disposed of in evaporation ponds, but is now generally re injected into deep wells or discharged into non-potable coastal waters. An estimated 35 percent of produced water requires disposal because it cannot be recycled. Past disposal practices and accidental releases of produced water could contaminate groundwater. Health and safety concerns at oil and gas fields include possible exposure to hydrogen sulphide, a poisonous and flammable gas that occurs naturally in oil and gas. It is an extreme health hazard because it can be fatal or harmful if inhaled. Hydrogen sulphide occurs in many areas marked with warning signs, but can be present in unidentified spaces.   Other safety concerns at oil and gas fields are open waste pits, abandoned wells, drilling equipment, cleaning and pumping activities, fires, explosions, and confined spaces where gases can accumulate.   A major environmental concern is natural gas flaring, which is the process of burning off gas during oil production. Gas flaring emits millions of tons of carbon dioxide each year. Other environmental concerns are damage to land and habitat, leakage of drilling fluids, and fires.   PDO have special procedures for managing H2S in the Southern fields of Al Noor, Birba and  Harweel  
Properties of H2S  ColourlessHighly toxicHeavier than airEmits odour from very low concentrations (Rotten egg smell)Soluble in water or oilFlammable in concentrations from 4.3% to 46%  
Factors Influencing ToxicityThe above indicates the levels of concentration of H2S and the associated affects. Note the increasing effects with increasing concentrations. Determinant of  health effects would be dependant on toxicity levels, concentrations, exposure duration, frequency of exposures and physiology and health condition of the individual The way in which H2S affects a person depends on the following: Duration – The length of time the individual is exposedIntensity – The concentration of exposureSusceptibility – The individual’s physiological make-upFrequency – how often the individual is exposed   Other factors include State of health.Age of individual.Route of exposure.Previous exposure levels.Workplace environmental factors.   Some individuals can be extremely vulnerable to H2S and it’s by- products.   The ability to tolerate exposure is reduced by health conditions such as:   Emphysema (disease of the lungs)       Bronchial asthma (Asthma is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing.)Epilepsy  (a brain disorder in which a person has repeated seizures (convulsions) over time.)Anemia (a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues.)Angina Pectoris (or other coronary artery disease) chest pain or discomfort that usually occurs with activity or stress. Progressive or severe hypertension (High blood pressure)   Individuals who have consumed alcohol within 24 hours of exposure are known to have been overcome by unusually low concentrations of H2S
Activity 8 List possible factors influencing degree of toxicity   1. _________________________________________________________     2. _________________________________________________________     3. _________________________________________________________   4. _________________________________________________________
Nitrogen Nitrogen Nitrogen is a common normally colourless, odourless, tasteless and mostly diatomic non-metal gas. It has five electrons in its outer shell, so it is trivalent in most compounds. Nitrogen in the environment Nitrogen constitutes 78 percent of Earth’s atmosphere and is a constituent of all living tissues. Nitrogen is an essential element for life, because it is a constituent of DNA and, as such, is part of the genetic code. Nitrogen molecules occur mainly in air. In water and soils, nitrogen can be found in nitrates and nitrites. All of these substances are a part of the nitrogen cycle, and there are all interconnected.

Humans have changed natural nitrate and nitrite proportions radically, mainly due to the application of nitrate-containing manures. Nitrogen is emitted extensively by industrial companies, increasing the nitrate and nitrite supplies in soil and water as a consequence of reactions that take place in the nitrogen cycle. Nitrate concentrations in drinking water will greatly increase due to this. Health Effects Nitrates and nitrites are known to cause several health effects. These are the most common effects:
– Reactions with haemoglobin in blood, causing the oxygen carrying capacity of the blood to decrease (nitrite)
– Decreased functioning of the thyroid gland (nitrate)
– Vitamin A shortages (nitrate)
– Fashioning of nitro amines, which are known as one of the most common causes of cancer (nitrates and nitrites)

Properties of Nitrogen  78% of air Gases asphyxiate by displacing oxygen Odourless, colourless, tasteless Non-toxic, non-flammable Causes dizziness, drowsiness, nausea, lack of consciousness, death   Liquid very cold causing irritation and burns to skin and eyes 
Permissible concentrations UK std EH40 
Activity 9 Complete the table correctly by inserting the correct letter for the health effect next to the given concentration level for H2S?   
Health effects of H2S The above table is for ref and guidance purposes only: 
Permitted exposure level (PEL)PEL refers to the concentration of a toxic substance that is judged safe for a worker to be exposed to. Also known as WEL (Workplace Exposure Limit)Also known as Threshold Limit Value (TLV) Based on an average concentration measured over  an 8 hour work day. (TWA ) Worker may be exposed for 8 hrs. per day, 5 days per week for years without ill health effects. European and international safety laws limit the amount of a toxic substance that it is legal to expose a worker to. These limits are chosen to ensure that continued exposure over months and years will result in no harm and no discomfort. So, at 5 ppm (the WEL for H2S gas) the worker will not be coughing or suffer from stinging eyes or other discomfort. This is based on an average concentration over 8 hours. PEL’s  for many chemicals are listed in a document called EH40 available on the website 
Time weighted Average (TWA)  The TWA for the exposure to a chemical can be used when both the chemical concentration and time for exposure varies over time. It is thus used as the average exposure to a contaminant to which workers may be exposed without adverse effect over a period such as in an 8-hour day or 40-hour week (an average work shift). They are usually expressed in units of ppm (volume/volume) or mg/m3 

A Short Term Exposure Limit (STEL) 
A Short Term Exposure Limit (STEL) is defined by the American Conference of Governmental Industrial Hygienists (ACGIH) as the concentration to which workers can be exposed continuously for a short period of time without suffering from: irritation chronic or irreversible tissue damage narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency.   
Immediate Danger to Life and Health (IDLH)  This is the concentration level of a toxic substance at which it may cause harm or make self-rescue difficult. For example, H2S at 100 ppm causes eye irritation which may make it difficult for a worker without eye protection to see clearly while trying to escape a hazardous environment. 
PTWRefers PTW standards applicable to all gas testing requirements in PR 1148 and PR 1172 
Activity 10   List the types of work that generally require gas testing.               
DefinitionsDangerous/hazardous work: Any work which has the potential to cause harm to employees Critical Task: A task if not performed properly has the potential to produce major loss to people, property, process and/or environment Practice: A set of positive guidelines helpful to performing a specific type of work that may not always be done in a set way. Procedure: A step-by-step description of how to proceed, from start to finish, in performing a task properly to completion. Task: Segment of work which requires a set of specific and distinct actions for its completion.  Examples include: Performing the pre-use inspection on an overhead crane.Setting up the wrapping machine for a pipeline joint.Performing an emergency shut down on the preheat furnace. Step: One segment of the total task where something happens to advance the work involved 
Flow chart for critical task analysis 
Standard ReferencesPR1154 Gas testing and PR1148 Entry into a Confined Space
Gas Test Requirements  PR-1172 – Permit to Work System Section 3.5 shall be referenced to determine the frequency of gas testing and the specific work it is required for. In general gas testing is required for the following types of work; §  Breaking containment §  Hot work in a process or hydrocarbon area §  Gas freeing and purging §  Confined space entry / work within a confined space §  Checking for suspected gas leaks §  Providing clearance for work activities §  Use of diesel engines in a process / hydrocarbon area §  Vehicle entry to a process / hydrocarbon area
Breaking Containment  Gas testing shall be required when containment is broken on any system containing hydrocarbon or toxic liquids / solids / vapours. Appropriate PPE and safety equipment i.e. SCBA, masks, face visors etc, shall be worn as necessary. The type of gas tested for shall be indicated on the PTW by the Area Authority in addition to the frequency of testing. Types of gas can include one or all of the following; HydrocarbonsH2SMercury (refer to PR-1515 – Onsite mercury Management) §  NORM (refer to SP-1170 – HSE Specification – Naturally Occurring Radioactive Materials (NORM)
Hot Work in a Process or Hydrocarbon Area  Hot work carried out in an area where hydrocarbons are present or can be present must be preceded by a gas test of the work site and adjacent areas to address the risk of fire and explosion caused by concentrations within the Lower Explosive Limits. The gas test shall be primarily for hydrocarbons and carried out in accordance with PR-1172 – Permit to Work System Section 3.5 and 6.2.4
Gas Freeing and Purging  Gas freeing of pipework and equipment shall be carried out prior to work being undertaken on hydrocarbon or toxic system. The normal medium for gas freeing is an inert, nitrogen or water. Gas testing of the pipework or equipment shall be carried out in accordance with PR-1172 – Permit to Work System Section 3.5 and PR-1073 – Gas Freeing, Purging, and Leak Testing of Process Equipment. During gas freeing processes using nitrogen the gas testing shall be to detect hydrocarbons in an inert and requires the appropriate testing equipment to be used
Confined Space Entry / Work within a Confined SpaceSpaces or vessels requiring entry by personnel to inspect or carryout work shall require to be tested prior to and during the work. Gas testing shall be undertaken in accordance with PR-1172 – Permit to Work System Section 3.5 and PR-1148 – Entry into a Confined Space Procedure. Confined space gas testing shall be to determine whether the atmosphere within the space can safely support life. Tests shall be for oxygen content and hydrocarbons / toxics.
Checking for suspected gas leaksSmall gas leaks in and around pipework and equipment may be detected using portable gas testing equipment.
Providing Clearance for Work ActivitiesWork activities in hazardous area shall require that the atmosphere at the work site and in the surrounding areas is safe before permission is given to carry out the work activity.  
Use of Diesel Engines in a Process / Hydrocarbon AreaThe use of internal combustion engines (diesel driven) within a process or hydrocarbon area shall be subject to authorisation and require gas testing in accordance with PR-1172 – Permit to Work System Section 3.5. Diesel driven plant i.e. mobile cranes, air compressors etc, shall be subject to continuous gas monitoring while in use. The units shall also be subject to a gas test prior to starting. The gas test shall primarily be to check for hydrocarbons.  
Vehicle Entry to a Process / Hydrocarbon AreaVehicles shall only be allowed into a process area if covered by a PTW. A PTW is not required for a hazardous area but gas testing is mandatory for both. Vehicles shall be subject to continuous gas monitoring while inside the area. The gas test shall be to check for an explosive or flammable atmosphere.  
Testing Instruments  Gas testing shall only be carried out by authorised ‘gas testing’ personnel who have completed the necessary training. These personnel shall be registered in PDO. Testing can be carried out using approved instruments. The following types are in use by PDO: – Multigas monitors (indication usually in % LEL or % Vol or ppm dependant on the gas being monitored) – Explosimeters (indication usually in % LEL) – Detector tubes (indication usually in ppm or volume) NOTE: When testing for mercury, NORM or hydrocarbons in an inert atmosphere specialist meters are required and the user shall be trained in its use.  
Multigas Monitors  Multigas monitors are capable of measuring a number of gases simultaneously. The gases monitored and displayed can include Flammable, Oxygen, Carbon Monoxide, Hydrogen Sulphide, Sulphur Dioxide, Chlorine, Nitrogen Dioxide, Ammonia, and Carbon Dioxide. The results are displayed continuously. The multigas meter is provided with a sample pump allowing for deep penetration testing of confined spaces and well cellars from a safe location. Audible and visual alarm is provided making the monitors suitable for deployment in the confined space or as perimeter guard for protection and warning
Explosimeter Monitors  Explosimeter are provided to measure only ‘flammable’ gases. The monitor will provide a measurement of the immediate area from which the sample is taken, which can be remote if sample lines and probes are used. The reading is displayed on a meter by needle deflection. The sensitivity of the instrument is set by the control ‘knob’. The instrument shall only be used by personnel who have undertaken the appropriate course.  
Detector Tubes  Detector tubes are single ‘spot’ check devices for detection of gases in the direct vicinity of where the sample is taken. Different detector tubes are provided for different gases, the selection of the detection tube being dependant on the gas being detected. A ‘fixed volume[3]’ sample is drawn through the detector tube by a hand pump. The detector tubes are calibrated and the change in colour observed will indicate the concentration of the gas present. In PDO the typical gas sampled for using detector tubes is H2S and CO2.
Pre-User Checks  Before using a portable gas detector (with exception of detector tubes) the following shall be observed: Ensure that the gas detector ‘test’ is in date. Do not use a gas detector that is ‘out of test’Check the gas detector for signs of damage. If damaged record and report the nature of the damage and exchange the gas detector for one that is undamaged (if possible)Before using the gas detector ensure the ‘battery’ is fully chargedAfter switching on purge the gas detector with uncontaminated airAllow the gas detector to complete the ‘startup sequence’ (if applicable) before useIf the gas detector uses a calibration gas check that the reading is correct to the calibration gasFollow all manufacturers safety instructions for use In both cases, the Authorised Gas Tester must: Gas test at the frequency stated on the Permit or Confined Space Entry Certificate.Fill in the result of the gas test on the Gas Test Record and Sign it. When a test result indicates that it is NOT safe to work, the Authorised Gas Tester must: Tell the Permit Holder to stop any current work. (see section 6.13 of PTW)Tell the Permit Holder and Area Authority that it is not safe to work, and why, so that the problem can be dealt with.
Atmospheric TestingAtmospheric testing is required to evaluate the hazards of the permit space and for verification that acceptable entry conditions for entry into that space exist. Similarly where ‘hot work’ is to be undertaken which is adjacent to live plant gas testing shall be undertaken to evaluate the risk of hydrocarbon or toxic gas.
Evaluation Testing  The atmosphere of the permit space should be analysed using test equipment for the specific gasesexpected to be present to identify and evaluate any hazardous atmospheres that may exist or arise, so that appropriate procedures can be developed to conduct the required work safely. Evaluation and interpretation of the gas measurement data, and development of the procedure, should be done by, or reviewed by technically qualified personnel based on a Risk Assessment.
Verification Testing  The atmosphere of a permit space which may contain a hazardous atmosphere shall be tested, using the appropriate gas test equipment to evaluate conditions are safe, at the time of analysis, to commence the required work. Results of testing (i.e., actual concentration, etc.) shall be recorded on the Permit to Work (PTW). “Measurement is by volume of the total atmosphere.”
Duration of TestingMeasurement of values for each atmospheric parameter should be made for at least the minimum response time of the test instrument specified by the manufacturer.
Testing Stratified Atmospheres  When monitoring for entries involving a descent into atmospheres that may be stratified, the atmospheric envelope shall be tested a distance of approximately 4 feet (1.22 m) in the direction of travel and to each side. If a sampling probe is used, the entrant’s rate of progress should be slowed to accommodate the sampling speed and detector response.
Order of Testing  A test for oxygen is performed first because most combustible gas meters are oxygen dependent and will not provide reliable readings in an oxygen deficient atmosphere. Combustible gases are tested for next because the threat of fire or explosion is both immediate and more life threatening, in most cases, than exposure to toxic gases and vapours. If tests for toxic gases and vapours are necessary, they are performed last.
PPERespiratory protective equipment Gloves Eye protection and hearing protectionHelmet Chemical Resistant Clothing Safety boots
Sampling for gasConsideration must be given to the environmental conditions when testing for gas eg is the wind blowing and how would that affect the movement of air perhaps inside a large storage tank that has to be entered for hot work purposes. Some gases are heavier than air and concentrations may accumulate depleting oxygen levels in…. Enclosed or confined spacesFlanges, valve stems, pressure relief valvesLow spots, pits and cellars, drains, ventsInstrument connections on pipework or vessels Some gases are lighter than air and concentration may accumulate depleting oxygen levels…. On top of storage tanks floating roof if below tank edgeAtmospheres may contain gases of differing density forming layers therefore tests should be conducted at all levels    
Hazardous environments
Working in Confined Spaces
Potential Hazards Associated with Confined Space Entry  In preparing for confined space entry ensure the potential hazards associated with confined space entry are recognised. These hazards can be any or all of the following: Oxygen deficiency or enrichmentFlammability (fire and / or explosion)Residual liquids, or solids and associated toxic or other noxious gasesChemical hazardsPhysical hazardsNumber of personnel working within the confined space and rescue access to themRestricted entry / exitNarcotic and anaesthetic effect of hydrocarbon gas and vapoursEmergency rescue equipment and methods
Planning and Risk Assessment  The first priority is to consider if the work in the confined space can be limited or avoided. Alternatives may be: Residues may be removed from the outside using water jetting or in place cleaning systems. In some cases it may be possible to see inside without entering by using a boroscope. Use of non-invasive inspection techniques   If the work is to be carried out in a confined space a risk assessment shall be completed covering all activities that will be carried out both inside and outside of the space. Personnel selected for confined space entry shall have the correct level of competence, experience and knowledge as indicated by the risk assessment. It will be necessary to include Vendors / 3rd parties or HSE professionals in this task.   The risk assessment will consider but is not limited to: Previous contents of the confined spaceInternal temperature and humidity of confined spaceIngress of substancesOxygen deficiency or oxygen enrichmentResiduesContaminationPhysical dimensions including internal structures or obstaclesNature of any work itself, including concurrent activities. The maximum number of personnel required to work in the confined space The outcome of the risk assessment process shall be a Job Safety Plan approved by the Responsible Supervisor, who shall determines what mitigation must be put in place based on the Risk Analysis. Where the risk assessment indicates that properly trained individuals can work for periods without supervision, it should be ensured that they are competent to follow the established safe system of work and have been provided with adequate information and instruction about the work to be done.
The Permit ApplicantThe Permit Applicant shall prepare a rescue plan as part of the Risk Assessment Process suitable for the agreed maximum number of personnel and covering each entry. This document should be reviewed and approved by the Responsible Supervisor. Some examples of possible inclusions to the rescue plan are:   Number of personnel required to provide effective rescue. The equipment required for immediate useContingency plans for loss of communicationSafest route of access and egress with respect to casualty handlingRemoval of unnecessary obstacles, which will hinder rescue operations   The Permit Applicant must appoint a trained rescue team before work begins. For efficient functioning, a rescue team must consist of at least two persons. The Permit Applicant must be sure that the designated rescue team can be deployed quickly in an emergency and that they will be able to function effectively. If assistance is required this shall be provided by the Area Fire Service.   The rescue team must be equipped with suitable personal protective equipment to enable them to function efficiently. Rescue plans covering the maximum permitted number of personnel will be agreed and practiced before any entry takes place. If it is not possible or practicable to perform training exercises before entry, it is the Permit Applicant responsibility to ensure all parties with responsibilities under this plan are competent in their roles.  
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Permit to workEntry into a confined space shall be controlled by a PTW. All persons holding safety competent roles e.g. gas tester, must be have valid PDO Passports showing their qualifications. Personnel required to work safely in confined spaces must have had adequate training and experience in the particular work involved. Training standards must be appropriate to the task, and to the individual’s roles and responsibilities, so that work can be carried out. In order to achieve the above the following conditions require being satisfied and / or detailed in the Job Safety Plan prior to entry into a confined space: All entries into a confined space shall be controlled by the PTW systemWhen entry is required, the confined space shall be physically isolated from all sources of hazardous substances, and from all sources of energy or motive powerHazardous substances contained within the confined space shall be displaced, and the space suitably cooled and ventilated; The confined space shall be tested for the presence of hazardous substances and for acceptable oxygen content. If conditions for safe entry cannot be achieved or guaranteed, additional precautions to be applied, e.g. the use of breathing apparatusProvision of personal protective clothing and equipment (personal gas detectors if required), access and egress, standby personnel, and rescue plansWhen a person is in a confined space a standby person shall be in attendance at all times and the responsible supervisor shall ensure that this person is authorised and fully briefed on the activity to be undertakenAdditional hazards, including concurrent activities in the vicinity of, or within, the confined space are consideredWhen entry to a confined space is required using breathing apparatus, only those persons trained and deemed competent in the use of the breathing apparatus shall be allowed to enter the confined spaceAll personnel involved in the confined space entry shall made aware of the hazards   CAUTION: Additional to the use of Portable Multi-Gas Testers confined spaces that have contained hydrocarbons shall be tested using a Photo-Ionization Detector (PID – e.g. Draeger tube) to confirm that Occupational Exposure Levels are complied with before an entry is made. This is particularly important for the very low exposure limits of the carcinogenic compounds such as Butane, Pentane and Benzene
Gas Freeing and Flushing  Tanks, towers and vessels that have contained hydrocarbon or toxic materials shall require gas freeing and ventilation before entry[4] can be made. Gas freeing shall be in accordance with PDO Procedures, PR-1073 – Gas Freeing, Purging & Leak Testing of Process Equipment (Excluding Tanks) and PR-1079 – Gas Freeing and Purging of Tanks Procedure. Once gas freed and drained[5] the confined space can be opened and ventilated. This method may be employed where high concentrations of toxic gases are encountered. Flushing with water (produced if available) shall be used on pipework, tanks, towers and vessels to remove heavy hydrocarbon deposits before opening for cleaning and / or maintenance and repair.  
Working Atmosphere  Gas testing of confined spaces shall only be carried out by an Authorised Gas Tester and shall be as specified on the PTW and recorded on the Confined Space Entry Certificate and the Additional Gas Test Record form (if required).
Oxygen  Confined spaces may only be entered when the atmosphere inside has been certified as having a safe oxygen (between 20%-21%) content as indicated by approved PDO detection apparatus. WARNING: If the oxygen content is less than 20% the vessel MUST not be entered.
Flammable atmosphere  Entry into confined spaces where there is any possibility of flammable vapours, gas testing with an approved PDO explosive meter shall be carried out and recorded. This meter must be capable of measuring hydrocarbons in an inert atmosphere if the confined space has been subjected to gas freeing using nitrogen. (examples are Ray Systems MX6 or MSA Tank scope.) The frequency of subsequent testing shall be stipulated on the PTW. If a reading greater than 0% is indicated the Responsible Person or his delegate must be notified and any required restrictions or precautions to be taken shall be entered on the “Confined Space Entry Certificates“. Flammable process hydrocarbon vapours are also hazardous due to their potential narcotic / anaesthetic effects, and can result in irrational behaviour, loss of consciousness, or even death. Hazardous concentrations can be related to flammability limits. Continuous ventilation shall be established within these spaces where possible.
Toxic atmosphereWhere toxic vapours may be present and continuous ventilation is not considered possible or feasible, each man entering the confined space shall wear positive pressure respiratory[6] protection. If NORM or Mercury is suspected then the necessary external and internal tests MUST be carried out by competent persons and the results checked and confirmed by the Production Chemists. If the tests are outside the specified limits, the confined space should be ventilated continuously and re-tested at regular intervals until acceptable. Further information on NORM and Mercury can be obtained in: SP-1170 – HSE Specification – Naturally Occurring Radioactive Materials (NORM) PR-1515 – Control of HSE Risks of Dealing with Mercury in PDO Facilities
Internal temp and humidity  For entry to spaces like Waste Heat Recovery Units of gas turbines, additional hazards may exist. These hazards exist due to the operational service where the space has been subjected to high temperature. Hazards such as internal temperature, humidity and hot surfaces should be included in the risk assessment, and suitable controls put in place. These controls could for example, result in work duration being reduced accordingly.
Breathing apparatus  For entry in to a confined space without the use of breathing apparatus, tests may include but are not limited to: Oxygen (between 20%-21%) H2S shall be no greater than 1ppm Benzene shall be less than 1ppm, but preferably zero Hydrocarbons in air less than 2% LEL but preferably zero (see Table) <2% Entry allowed without BA ≥2% and <10 or atmosphere unsustainable Entry only with BA ≥ 10% No entry allowed       CAUTION: If it is considered that, the breathable atmosphere cannot be guaranteed then entry shall be completed wearing breathing apparatus.
Ventilation  Ventilation shall be employed to make the atmosphere inside of the confined space able to ‘support life’. Where the atmosphere in the confined space is flammable or toxic, forced ventilation will be employed to extract and clean air be allowed to replace that extracted by natural circulation from a low point. WARNING: Outside air shall not be forced in to expel the flammable atmosphere as this may cause an explosive mixture being formed. When dealing with vessels and tanks etc, that are have a risk of pyrophoric deposits being present within the internals reference should be made to PR-1077 – Preparation of Static Equipment for Internal Maintenance and Inspection Section 4.2 Confined Space Entry.  
Positive Isolation  Before any entry is permitted to a confined space positive isolation shall be carried out as required. Process equipment and systems shall be positively isolated as detailed in PR-1076 – Isolation of Process Equipment. MECHANICAL Mechanical isolations shall be carried out using ‘spades and blind’ where applicable, or removal of spool pieces where applicable. ELECTRICAL Electrical shall be isolated at the MCC or switchboard. All isolations should be carried out by a ‘competent person’ and be tagged in accordance with SP-1104 – Electrical Safety Rules and the issue of an Electrical Isolation Certificate which shall be attached to the PTW.  
Use Naked Flames and Arc  Strict control shall be exercised on the use of ‘naked flames or arc welding’ equipment inside or in the vicinity of confined spaces where flammable vapours are or could be present. Such works shall require a Hot Work Permit’ to be in force.   Fixed and portable fire equipment, correct for the type of work being undertaken, shall be provided at and adjacent to the work place.   WARNING: CO2 or dry powder type extinguishers shall not be used inside of confined spaces when personnel are inside. Accordingly water shall not be used if ‘live’ electrical equipment is being used inside the confined space. In the event of a fire personnel shall be evacuated as quickly and safely as possible.  
Personal protection equipment  Correct PPE shall be worn at all times while the work is being undertaken. Specialised PPE required for specific tasks shall be made available to all personnel involved. The requirements of specialized PPE shall be made on the Job Safety Plan.   SAFETY HARNESSES / LIFELINES Safety harnesses shall be provided for all persons working inside the confined space if the work involves scaffolding or ‘raised’ platforms. Suitable ‘strong points’ shall be made available if not already provided. Lifelines shall be used at all times by personnel inside the confined space. PORTABLE POWER TOOLS Where practical power tools used within confined spaces shall be ‘pneumatic’. Use of electrically powered equipment shall be kept to a minimum and be in accordance with SP-1111 – Temporary Electrical Supplies for Construction & Maintenance Work. The preference shall also be made to adopt pneumatic lighting for confined spaces rather than those powered from electrical circuits.  
Confined Space Entry Process  The following process shall be followed or adapted when undertaking work which requires ‘entry into a confined space’. The following Permits and Certificates are associated with Confined Space Entry: Permit to Work (PTW)Confined Space EntryMechanical IsolationAdditional Gas Test RecordElectrical Isolation The Permits and Certificates shall be completed, signed and attached to the PTW with a Job Safety Plan (including Risk Assessment) and all relevant drawings and documents.   Refer page 16 of PR1148 for more detail  
Working With Nitrogen Gas  Objective This Appendix will identify the precautions and procedures that should be observed when working with nitrogen, and when inerting systems using nitrogen gas for purging. WARNING: NITROGEN IS AN ASPHYXIANT AND WILL NOT SUSTAIN LIFE. General Nitrogen is the main component of breathable air and, as such, is often wrongly considered not to be a personal hazard. It is provided for use either in a gaseous form in `quads’ or from a nitrogen- producing skid, or in a liquid state in cryogenic bulk tanks where it is stored at a temperature below its boiling point of -196°C. If undiluted nitrogen is breathed, not only is the blood passing through the lungs not replenished with oxygen, but also much of the residual oxygen in the blood passes out into the lungs. The effect is therefore much worse than holding one’s breath or re-breathing air. In practice it will take only a few breaths to fully exchange the air in the lungs for nitrogen, and unconsciousness will rapidly ensue. There is no warning because the normal stimulus to respiration is the build-up of carbon dioxide, not lack of oxygen. Carbon dioxide will not build up while breathing continues if the gas being breathed is nitrogen. Fatalities and serious injuries have occurred when performing activities on equipment that has recently contained nitrogen. This has happened when, in order to make progress with the work, sheeting, tarpaulins, boarding etc. have been used to screen or protect the work site, and a confined area has been created around the equipment. Great care must be taken to ensure that a confined space is not created, whether deliberately or inadvertently, which might allow the uncontrolled build-up of nitrogen and the consequent exclusion of oxygen. Where it is deemed necessary to operate within a confined space that has recently contained nitrogen, an oxygen meter shall be used to continuously monitor the atmosphere. Liquid nitrogen, released into the atmosphere in an uncontrolled manner, will quickly change form to a gas, thus producing an asphyxiation hazard from the nitrogen-enriched atmosphere.   Precautions Prior to using nitrogen in either a gaseous or cryogenic form, an assessment of the risks to both personnel and equipment, from leaks or spills, shall be carried out. Particular attention should be paid to: Provision of drain paths for spills and leaks.Routes for temporary hoses.Provision of First Aid equipment and competent persons to use it.Written procedures for the operation, including emergency procedures for dealing with spills and leaks. All work involving the use of nitrogen shall be controlled by the Permit to Work (PTW) System. Barriers and warning notices shall be erected around the work area. All openings, man ways, pipe ends etc. must be clearly marked, and oxygen monitoring and rescue equipment provided. All personnel involved in the operation shall be instructed in the hazards associated with nitrogen operations and the types and functions of monitoring equipment being used. Where habitats or partial enclosures are required, these shall be treated as Confined Spaces, and the controls and precautions associated with Confined Space entry shall be applied.  
Facility H2S Classification Management  Currently facilities within PDO shall be classified under one of the following categories: H2S Concentration (ppm) in the Gas Phase Category 0 to 49 Sweet 50 to 499 Low Risk Sour > 500 High Risk Sour (Further Assessment based on Quantitative Risk Assessment)   Very High Risk Sour (classification based on Quantitative Risk Assessment)[7]   For ‘further assessment’ i.e. >500 ppm in gas stream the concentration at potential leak points is used to establish the correct category. The assessment takes a distance of 2 meters from the potential leak point and calculates the H2S concentration in air. If the calculations indicate the concentration to be < 200 ppm then the site will be categorised ‘low risk sour’; if above 200 ppm then the category shall be ‘high risk sour’. This does not apply to Very High Risk Sour.  


JOB:Repair Thermocouples on
Liquid Burner Flare
I Sweatalot (Rigger), R Puller (Inlec),
D White (Tech haul)
TEAM MEMBERS: Brad Pollock, Coke Black (Rigging Foreman)DATE:    29.2.99
1.Isolate power services.Burner could operate.  Risk of electrocution.Obtain relevant permits to work.
2.Run leads up tower.Risk of falling from height (workman).  Falling objects.Use licensed rigger for all work outside handrail.  Wear safety harness and lanyard. Standard PPE.  Station man at chain barrier as watchman to restrict access.
3.Communications.Not understanding signals.Have radio communications top and bottom.
4.Raising tools/equipment by hand.Items may fall.Use lifting basket and inspect equipment.
5.Replace earth straps under burner chamber.Risk of falling from height.(As per No. 2).
6.Replace thermocouples.Use of ladder on buckled floor.Standby at base of ladder.  Ladder to be lashed at top.  Person on ladder to use safety harness.
7.Connect thermocouples.Dropping tools/meters.Keep tools in bag on walkway.  Keep people clear below.
8.QA/QC inspection.Falling objects.Restrict access.  Coordinate work above to allow access.

[1] Newly fabricated or shot blasted carbon steel vessels are especially vulnerable to corrosion

[2] Volatile organic compounds, or VOCs are organic chemical compounds whose composition makes it possible for them to evaporate under normal indoor atmospheric conditions of temperature and pressure

[3] The volume of sample required to be drawn through the detector tube varies with the gas being sampled for. Reference shall always be made to the kit instructions to ensure that the correct volume of sample is obtained.

[4] This may not be the case if the tank or vessel is to be washed and cleaned prior to gas freeing and ventilation. In such cases personnel entering the space shall be equipped with breathing equipment.

[5] When using water to gas freeing tanks, towers and vessels ensure that high level vents or man ways / access hatches are open to prevent drawing and negative pressure and risking collapse.

[6] Respiratory protection for each man in the confined space and for the Standby Personnel must be provided where the Responsible Supervisor / Permit Holder consider it necessary. At least one properly connected air mask shall be available outside of the confined space for rescue purposes. This should be included on the JSP.

[7] Very High Risk Sour can be defined as an area where the use of Self Contained Breathing Apparatus shall be worn whilst performing any activity (Red Zones) – Applicable to Harweel Development.