CONTENTS. 9. Opening of gas systems containing H 2 S. 1. Introduction. 8. Protection of Personnel.

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2 CONTENTS 1. Introduction. 2. Properties and toxicity of H 2 S. 3. Physical effects of H 2 S. 4. Pyrophoric iron sulphide. 5. Identification of H 2 S hazard. 6. Entry to H 2 S risk area. 7. Detection of H 2 S. 8. Protection of Personnel. 9. Opening of gas systems containing H 2 S. 10. Responsibility of Supervision 11. Rescue and first aid.

3 1. INTRODUCTION Hydrogen Sulphide (H 2 S) is one of the most toxic gases handled in the oil and gas industry. It is absolutely essential that all employees have a clear understanding of the very hazardous nature of H 2 S, the recognition of its presence, and the procedures to be followed in order to protect themselves from its s lethal effect if H 2 S is released into the atmosphere. H 2 S may be released into the atmosphere during operations such as draining, venting, sampling and when process equipment or pipework is opened for maintenance work. It can also be released to the atmosphere due to the leakage of crude oil or natural gas containing H 2 S. The purpose of this code of safe practice is to aid the understanding nding of all personnel and to clarify safe working procedures for personnel who w may be exposed to H 2 S. H2S KILLS - BE AWARE - BE SAFE

4 2. PROPERTIES AND TOXICITY OF H 2 S

5 H 2 S is a highly toxic gas. It is colorless and is heavier than air; having a vapor density of 1.2 it tends to settle in low-lying lying areas. However it is readily dispersed by wind movement. Soluble in water: 4 volumes of gas in 1 volume of water at 0oC. It is flammable and, if ignited, will burn with a blue flame, producing Sulphur Dioxide (SO 2 ) an irritating and also very toxic gas with a pungent odour. Auto-ignition temperature is 292oC.. When mixed with air in certain proportions within the flammable limits it will explode upon ignition. ition. Lower Flammable Limit is 4.3 % v/v Higher Flammable Limit is 46.0 % v/v H 2 S has a characteristic 'rotten eggs' odour which can be smelled in concentrations as low as 0.1 part of gas per million parts of air r by volume (ppm).

6 The odour is very unreliable way of detecting this poisonous gas. At concentrations between ppm,, the sense of smell is rapidly deadened.. This can be fatal to a person who thinks that a dangerous concentration can be detected by the offensive odour. DO NOT DEPEND ON SMELL TO DETECT H 2 S. It should be detected At low concentrations, H 2 S causes irritation to the eyes, nose and throat, and in high concentrations can be rapidly fatal due to lung paralysis. The Threshold Limit Value (TLV) is the time weighted average concentration for an 8-hour 8 day or 40 hour week to which nearly all workers may be repeatedly exposed without adverse effect. The TLV for H 2 S is 10 ppm.

7 3. PHYSICAL EFFECTS OF H 2 S

8 The affect of H 2 S on a person depends on: The concentration of exposed, The length of time of exposure and The body tolerance. Measured in air by volume: 0.1 ppm Minimal perceptible odour 27 ppm Strong, unpleasant odour,, but not intolerable 50 to 100 ppm Eye and respiratory tract irritation. 200 to 300 ppm tract Marked eye inflammation and respiratory irritation after exposure of one hour. 500 to 700 ppm Dizziness, headache, nausea,...etc., within 15 minutes; loss of consciousness and death after 30 to 60 minutes. 700 to 900 ppm Rapidly produces unconsciousness then death. Over 1000 ppm Apparent death is instantaneous. No evidence has been found that repeated exposure to low levels of H 2 S will accumulate in the body. After exposure to moderate concentrations, symptoms will disappear after removal from the exposed area.

9 4. PYROPHORIC IRON SULPHIDE In the absence of air, H 2 S can react with iron or iron scale to form pyrophoric iron sulphide.. This will oxidize to iron oxide in the presence of air, and this exothermic reaction can cause localized heating to a temperature which is sufficient to ignite any flammable material which may be present. Vessels and pipelines which have contained gases or liquids and which have had air partially or completely excluded may contain pyrophoric materials. This covers gases or liquids with a sulphur content, especially hydrogen sulphide. Pyrophoric materials when dry and exposed to air will ignite spontaneously and could be the cause of a fire or explosion. These materials must be removed in a wet state. Gas freeing techniques based on inert gas (nitrogen) or water prevent ignition of pyrophoric material, but if eventually air is allowed to enter, it is imperative that no flammable vapour remains.

10 5. IDENTIFICATION OF H2S HAZARDS Equipment, pipelines or complete process areas containing hazardous concentrations of H 2 S should be clearly identified. Equipment or areas identified as a High Risk Area, i.e. 500 ppm or more, shall be clearly identified and toxic hazard notices displayed at the boundary of the area.

11 6. ENTRY TO H 2 S RISK AREA Entry to these areas must be strictly controlled with access requiring written authorization from the client representatives. Precautions as mentioned in the authorization certificate (work permit) should always be strictly adhered to.

12 7. DETECTION OF H 2 S

13 Your sense of smell is usually first in warning you of the presence of H 2 S, but unfortunately may be last. DO NOT RELY ON YOUR SENSE OF SMELL TO TELL YOU HOW MUCH H 2 S GAS IS PRESENT When testing for the presence of H 2 S, it is prudent to be prepared for lethal concentrations. The equipment available will depend on the potential level of hazard. The following methods of detecting the presence of H 2 S are used. Dragger Detector Tubes: The concentration of H 2 S present is registered by the length of discoloration when the sample of atmosphere is drawn through the detector tube. Fixed Leak Detector System: analyses the atmosphere continuously for the presence of H 2 S and gives an audible warning when the H 2 S concentration gets above a fixed limit. are placed in high-risk areas. Portable H 2 S Detector Alarm Gives an audible alarm when the concentration is 10 ppm or greater.

14 8. PROTECTION OF PERSONNEL

15 a) Precautions: Meticulous planning is necessary when work is to be carried out in an area where H 2 S is a potential hazard. Problem situations should be eliminated beforehand, not when life is at stake. Entry and working procedures in H 2 S risk areas and on H 2 S equipment must be strictly controlled at all times. Safety precautions should include the following: All personnel to know how to approach the work site taking into consideration wind direction, and movement of personnel. Elimination of all sources of ignition because H 2 S is extremely flammable. Use of breathing apparatus with a standby and if appropriate, use of lifelines. Availability of at least two escapes routes. Air monitoring or detection equipment with appropriate alarm system. Observation of warning signs. Use of reliable communications.

16 b) Breathing Apparatus (B.A.): Personal protective equipment is not an adequate substitute for safe working practices and controls, but at times it is the only practical means of protecting persons carrying out work in H 2 S risk areas. Personnel required to work in an H 2 S risk area and who may be exposed to a dangerous concentration of H2S shall wear suitable breathing apparatus of the self-contained positive pressure (or airline mask) and if appropriate, safety belts with lifelines to permit easy rescue should the need arise. Using this apparatus the wearer is i quite independent of the harmful environment, and carries his own supply of life supporting air (oxygen). An additional person must be in attendance, and shall have suitable B.A. immediately available e for use. This person should stand at a safe distance to render assistance stance or call for help in case of need. Escape type breathing apparatus shall be provided for use in an emergency. Emergency equipment must be used for emergencies only. It is essential that every user is aware of and understands the limitations of the type of breathing apparatus made available. Breathing apparatus should be worn by personnel who have received training in its use and limitations.

17 c) Types of Positive Pressure Breathing Apparatus: Self-contained breathing apparatus: This type of apparatus supplies air from a cylinder worn on the back. In this apparatus, a positive pressure is maintained at all times s inside the face mask, even during inhalation, thus 'positively' preventing any inward leakage around the face seal. Positive pressure lowers the respiratory load, giving increased comfort to the wearer. Generally the supply of air is for 30 minutes duration. Escape sets are of 10 minutes duration. Supplied air breathing apparatus: This type of apparatus is very light to wear and gives the wearer r an extended positive pressure air working duration. If the supply of air is from a compressor, it is necessary to filter the air before it is supplied to the man and also to have an emergency supply of air available should the compressor fail. The supply of air can also o be made available from a set of high-pressure compressed air cylinders. Supplied air breathing apparatus restricts the wearer's movement to the length of the hose (supplying the compressed air), and also forces the wearer to return by the same route when leaving the work w area.

18 d) Effects of Physical Activity on Breathing Effects of Physical Activity on Breathing Physical activity or increased work levels of a person affects his h breathing rate and the volume of breathing air. As the activity increases, so a larger volume of air per unit of time is required. Air flow rates required vary with the different types of work being carried out and of course the person. Average examples are shown below: Activity Air Flow Rate Sleeping 6 (liters per minute) Resting 10 Light work 20 Medium work 29 Medium Heavy work 40 Heavy work 60 Maximum work level 132

19 e) Problems with the Use of B.A It is recommended that employees with certain health problems should not work in an atmosphere requiring the use of B.A. However, if any doubt exists as to a person s s health the doctor should be consulted. Some of the health problems which may limit the wearing of breathing apparatus are: A perforated ear drum (this may allow passage through the Eustachian Tube into the respiratory tract) Bronchial asthma Angina pectoris (know as heart-stroke) Claustrophobia Diabetes For persons wearing prescription spectacles: face pieces are available which allow continued wearing of spectacles whilst using B.A. for work.

20 f) Canister Respirators (H2S masks) Canister respirators (filters) only give protection in certain low l concentration gas-laden atmospheres up to a maximum of 2% volume gas or a limited time. It must not be used in oxygen deficient atmospheres and never used in confined spaces. Canister respirators, where available, should be used for escape only and must not be used for doing work.

21 9. OPENING OF GAS SYSTEMS CONTAINING H2S

22 When preparing a system for opening, the aim must be to isolate, depressurize and purge before work starts on opening a gas system. It may not always be possible to meet this aim, but the work can still be carried out safely provided that the hazard is recognized and the proper controls and precautions are applied and maintained. It is the responsibility of the client authorities to clear that the specific system can be opened and to specify the required precautions, which must be carefully applied.

23 10. RESPONSIBILITY OF SUPERVISION

24 Be alert to unsafe conditions and act. Take immediate and appropriate steps when H 2 S is detected or Suspected. Stop the work and deactivate any source of ignition. Set a good example. Ensure that your personnel followf safe working practices, and fully understand how to use breathing apparatus and escape safely.

25 11. RESCUE AND FIRST AID

26 In the event of an emergency where a person has been overcome by H2S -remain calm - THINK!! PUT ON YOUR BREATHING APPARATUS BEFORE ATTEMPTING TO RESCUE A PERSON IN TROUBLE. IF YOU DO NOT - YOU WILL BECOME A VICTIM OF H2S. Move the victim to a safe (fresh air) ) area. (Go upwind of source of H2S release NOT downwind). If victim is not breathing, start artificial respiration immediately. Summon medical help.. Keep victim warm. Continue giving artificial respiration until the doctor arrives.

27 If available, use a resuscitator,, but only if properly trained in its use. If a victim is moved to fresh air and normal respiration is restored before the heart action ceases, then fairly rapid recovery usually occurs. If the person s s eyes are affected, wash well with clean water. If a person suffers minor exposure to H 2 S, and has not been completely unconscious, it is recommended that he rests for about 8 hours, in order that his reflexes may return to normal.