1. Rev. 1 © Chevron 2009 Gas and Vapor Detection Awareness Plus

2. Rev. 1 © Chevron 2009 2 Outline Critical Components for Gas Testing include:  During planning stage determining what types of gas test is required When applicable refer to the MSDS Sheets for the product the equipment to be isolated  Verifying the gas testing instruments to be used are in good operating condition  Ensure that all safety precautions required to perform gas testing are in place and followed  Conduct required gas tests  Evaluate, interpret and record the test results We will also look at the operation principles of some portable gas detection instruments to understand some of their shortcomings.

3. Rev. 1 © Chevron 2009 3 Introduction  In the experience of a leading expert in the field of gas and vapor testing the majority of people he has encountered over the years of training and discussion, mainly in the petroleum industry, have led him to the conclusion that most could have been or were using even the simplest of gas detectors in misleading, and possibly dangerous ways. Such misuse of the gas detector can not only produce erroneous readings, but also endanger the lives of everyone in the vicinity. Note: The safety of everyone involved depends upon the recognition of potential contaminant gases or vapors and the correct selection and use of the gas detection instruments to measure these.

4. Rev. 1 © Chevron 2009 4 Why do we need to perform gas testing? The Straits Times, Singapore Friday, August 24 2001 Three Filipino crew members on a Singapore- registered tanker were overcome by petroleum gas and one died yesterday morning. The incident took place in waters West of Singapore’s port limits, said the Maritime and Port Authority of Singapore (MPA) in a statement yesterday. The three crew members were cleaning the cargo tank on board the MT Orchid, a petroleum tanker managed by Neptank, at about 10 am when they were overcome by the residual gas.

5. Rev. 1 © Chevron 2009 5 Determining Gas or Vapour Concentrations  Gas testing is undertaken to determine the presence of flammable and or toxic vapour or gas, and at what concentration are present.  Gas Testing is done to ensure that no hazardous work conditions exist from the presence of such gases or vapors.  The principal areas of concern for human safety are: Determining oxygen levels (deficiency or enrichment) Determining explosive risks (flammability) Determining health risks (toxicity)

6. Rev. 1 © Chevron 2009 6 Planning for Gas Tests  Prior to commencing work in an area which may contain hazardous gases or vapors the person in charge should identify hazardous substances or conditions that may require gas testing, such as: Oxygen deficiency or enrichment Flammable gas or vapor Toxic vapors such as: ► benzene or organic lead ► Hydrogen sulfide ► Carbon monoxide ► Carbon dioxide  During the planning stage for proposed work the following should be determined; The types of gases that need to be tested for; What the acceptable limits are; The frequency of gas testing required

7. Rev. 1 © Chevron 2009 7 Calibration and Response Testing  All gas detection equipment shall be calibrated in accordance with the manufacturers guidelines and/or local standard requirements.  Field calibration testing should be done and the results recorded on a monthly bases.  The gas test instrument should be response checked (bump tested) before each work shift, or before use if not used on every work shift. Response check (bump test) requires the manufacturer’s calibration gas to be used.  Response checks/bump tests should be carried out using the manufacturer’s recommended test procedures and equipment

8. Rev. 1 © Chevron 2009 8 Review Manufacturers Precautions  Prior to using gas detection equipment the user must be aware of any manufacturers precautions. Review the Owner’s Manual and Operating Manual for your specific gas detection equipment (if you don’t have these, get them!).  These may vary depending on the manufacturer and type of sensor being used.  Typical warnings that may apply include: Oxygen deficient or oxygen enriched environments may cause erroneous LEL readings. Ensure sufficient battery charge before use. Only recharge or change batteries in a non-hazardous area. Do not draw liquid into the sampling line. Only zero the instrument in clean air. Sampling environments with more than 100% LEL may provide erroneous LEL readings. Do not remove instrument from it’s case when in a hazardous environment.

9. Rev. 1 © Chevron 2009 9 Conduct Gas Tests  Only Qualified Gas Testers are authorized to conduct gas tests  Many client Company will not lend their gas testing equipment to contractors, they require them to have their own gas testing equipment  Test the work area atmosphere for the identified hazards.  Testing should start in a known safe area and move into the work area to be tested.  Tests should be done in the following order: Oxygen Flammable gases Toxic vapors

10. Rev. 1 © Chevron 2009 10 Conduct Gas Tests cont.  Test in area where flammable or toxic gases/vapors are likely to accumulate.  Any tests which indicate readings outside the acceptable range should result in the area being cleared of all personnel and the area ventilated until a safe environment is obtained.  Appropriate PPE must be worn when testing (e.g. respiratory protect required when initially testing inside a confined space such as a tank).  Any alarm activation on the test instrument should result in an immediate evacuation of all personnel out of the area until the reason for the alarm is determined and corrective measures taken.

11. Rev. 1 © Chevron 2009 11 Interpreting Gas Test Results  All work must be stopped whenever a test indicates a hazardous condition exists  Gas detection instruments may read out in a number of scales: ppm - parts per million (or ppb, parts per billion) mg/m³ - milligrams per cubic metre % v/v – percentage volume per volume % LEL – percentage of lower explosive limit  It is important to understand what measurement scale is being used on the instrument you have and ensure this matches the acceptable limits scale. Note: some multi-gas instruments may read in several different ways (e.g. read flammable atmosphere in %LEL, oxygen level in % v/v, and H2S level in ppm)

12. Rev. 1 © Chevron 2009 12 Typical Scenarios for Gas Testing  The following are some typical examples where gas testing would be required at a facility: Before performing Hot Work or entering a Confined Space. When responding to a spill of hazardous materials. Entering an oily water separator to clean or carry out repairs. Entering inside a bulk storage tank, or any other confined space. Downwind of a tank being degassed, including boundary measurements if near a site boundary. Carrying out welding (or other hot work) inside a tank compound. Opening of live electrical boxes inside a hazardous zone.

13. Rev. 1 © Chevron 2009 13 Gas Detection Devices  Instruments may use a number of different principles of operation to measure gas and vapor concentrations. These may include: Colorimetric Catalytic combustion Electrochemical  Instruments in common day-to-day used typically have catalytic combustion sensor for LEL and electrochemical sensors for Oxygen, HES, CO, etc. All Sensors have a limited life expectancy, refer to the manufacturer’s recommendations.

14. Rev. 1 © Chevron 2009 14 Catalytic Combustion  Flammable Gas Detection Principal Catalytic combustion on heated filament Filaments are part of Wheatstone bridge Increase in temperature causes an imbalance in the bridge and an increased current flow Current flow is measured and is proportional to concentration of combustible gas

15. Rev. 1 © Chevron 2009 15 Catalytic Combustion Instruments  Require oxygen to be present to enable combustion process. There must be a minimum of 16% Oxygen present for LEL sensor to read properly.  Only reads the sample that passing the sensing wires where the catalytic reaction occurs.  Require the sample to be ‘drawn’ past the sensing wire (at a defined rate of flow). Refer to the Gas Test Instrument’s manufacturer’s specifications  Give an indicative reading only, not a specific concentration reading.

16. Rev. 1 © Chevron 2009 16 Filament ‘Poisons’  Poisoning of filaments results in loss of catalytic ability which leads to reduced sensitivity. Some typical ‘poisons’ for catalytic elements include : Tetraethyl lead. Silicon containing products (e.g. furniture polishes, silicone rubber compounds, etc.). Halogenated hydrocarbons. Some hydraulic fluids and lubricants (if very hot). Volatile sodium and potassium compounds.

17. Rev. 1 © Chevron 2009 17 Electrochemical Sensors  Essentially the same principle as a battery.  They use two ‘electrodes’ in a cell, separated by an ‘electrolyte’.  Sample is normally by diffusion onto the cell.  Works by ions being collected which creats an electron flow in the presence of the target gas e.g. Oxygen + Lead = Lead Oxide + Electricity  Flow of electrons created is directly proportional to the amount of gas present.

18. Rev. 1 © Chevron 2009 18 Oxygen Meters  Detection Principle Galvanic cell filled with electrolyte Oxygen diffuses into cell and goes into solution  Factors that may Influence Accuracy Temperature Altitude Humidity  Limitations/Advantages Oxygen specific – no significant interferences Calibrate the instrument at the temperature and altitude at which it will be used. Once opened, the oxygen cell has a limited life span. ► Typically 1 - 2 years (depending on manufacturer) ► Replace the cell when it reaches the end of its life expectancy or; ► Replace the cell whenever it can no longer be calibrated to 20.9%

19. Rev. 1 © Chevron 2009 19 Use of Colormetric Pump  A colormetric pump and relevant tubes are often used to test for the presence and concentrations of various toxic vapors that may be present. For example there are colormetric tubes in various ranges for detection of Benzene, Carbon Monoxide, Carbon Dioxide, Mercury, Hydrogen Sulfide, etc  Colormetric pumps and tubes may also be used to determine the total hydrocarbons present at a job site to determine if respiratory protection is required.

20. Rev. 1 © Chevron 2009 20 Detection Requirements  In order for a gas detection instrument to work correctly: The product being detected must be in a vapour or gaseous state. The instrument must be drawing a sample from where the gas/vapour will have accumulated. (i.e. Is the gas/vapour potential to be present lighter or heavier than air). Must ensure the gas test instrument’s sensor filament has not been ‘poisoned’ by conducting required bump testing. The equipment must be given time to allow temperature of the instrument to stabilize if it is stored in a location where the temperature is different that the location tests to be performed in. Be aware of CHANGING CONDITIONS.

21. Rev. 1 © Chevron 2009 21 Other Issues to Remember  Avoid sucking liquid into the instrument  Ensure any calibration gas is the correct gas and concentration for the instrument to be calibrated.  Response check (bump test) kits are generally not interchangeable between various manufacture models.  Most gas detection instruments are indicators only so treat any reading as a potential danger until you can validate the reason for the reading.  Adopt a ‘Read and Run” principle to gas testing – always be prepared to retreat to a safe area when testing.  Gas testing for toxic vapors such as Benzene, etc is normally be performed using a colormetric pump and tubes of the proper type and range.

22. Rev. 1 © Chevron 2009 22 Other Issues to Remember (cont)  Flammable hydrocarbons with a high flash point will not under normal conditions give off vapors unless their flashpoint temperatures are reached. For example diesel will not give off any vapors at ambient temperatures less that its flash point.

23. Rev. 1 © Chevron 2009 23 Gas Testing – Additional Information For further instructions and additional information for Gas Testing please refer to:  Gas Detection Safety Bulletin  Your companies operating procedures and gas testing equipment manufacture’s Owner’s Manual and Operating Instructions;  Your Company’s Safety Officer  The clients Safety Department’s Representative