1. Combustible Gas & Oxygen Meter

2. Combustible gas indicators (CGIs) measure the concentration of a flammable vapor or gas in air, indicating the results as a percentage of the lower explosive limit (LEL) of the calibration gas.

3. Combustible Gas & Oxygen Meter Principle of Operation The LEL (or LFL - lower flammable limit) of a combustible gas or vapor is the minimum concentration of the material in air which will propagate flame on contact with an ignition source.

4. Combustible Gas & Oxygen Meter Principle of Operation Above the UEL, the mixture is too "rich" to support combustion so ignition is not possible. Below the LEL there is insufficient fuel to support combustion.

5. Combustible Gas & Oxygen Meter Limitations & Considerations Temperature Temperature Oxygen Levels Oxygen Levels Interfering Coumpounds Interfering Coumpounds  Organic Lead  Sulfur compounds  Silicone  Acid Gases

6. Combustible Gas & Oxygen Meter Calibration is performed with calibration gas, which contains precise concentrations of several gases. Calibration is performed with calibration gas, which contains precise concentrations of several gases. Meter is calibrated to calibration gas for LEL, therefore correction factors must be applied when using detector on other types of gases. Meter is calibrated to calibration gas for LEL, therefore correction factors must be applied when using detector on other types of gases.

7. Combustible Gas & Oxygen Meter Hot wire operation-test gas is passed over a heated wire(sometimes in the presence of a catalyst). The test gas burns, changing the temperature of the filament, and the electrical resistance of the filament is measured. Hot wire operation-test gas is passed over a heated wire(sometimes in the presence of a catalyst). The test gas burns, changing the temperature of the filament, and the electrical resistance of the filament is measured.

8. References Cited NIOSH Manual of Analytical Methods (NMAM®), 4th ed. DHHS (NIOSH) Publication 94-113 (August, 1994), Cassinelli, M.E. & O'Connor, P.F. (pfo1@cdc.gov), Eds. O'Connor, P.F. (pfo1@cdc.gov)O'Connor, P.F. (pfo1@cdc.gov)

9. Bibliography DiNardi Salvatore R. (1998) The Occupational Environment-Its Evaluation and Control, AIHA, Fairfax, Virginia DiNardi Salvatore R. (1998) The Occupational Environment-Its Evaluation and Control, AIHA, Fairfax, Virginia Goetsch David L. (1999) Occupational Safety and Health for Technologists, Engineers, and Managers, Prentice Hall, Upper Saddle River, New Jersey Goetsch David L. (1999) Occupational Safety and Health for Technologists, Engineers, and Managers, Prentice Hall, Upper Saddle River, New Jersey