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Comparison of selected lower explosive limit meters used by USAF and commercial jet fuel tank entry personnel.

Jensen P; Martin S; Sapko M; Lazzara C; Mura K; Smith L; Fritts D; Blazicko B; Reichert J; Pleil J

American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida. Fairfax, VA: American Industrial Hygiene Association, 2000 May; :76

20041646

Thousands of military personnel and tens of thousands of civilian workers perform tank entry procedures. OSHA regulations (§ 1910.146) require the internal atmosphere be tested with a calibrated direct-reading instrument for oxygen content, flammable gases and vapors, and potential toxic air contaminants before an employee enters the space. The U.S. Air Force and NIOSH previously identified the highest worker exposures during removal of fire suppressant foam from the fuel tanks of Hercules C-130H aircraft. In addition, the study noted that jet fuel vapor composition changed with time and ventilation. In this study, lower explosive limit (LEL) meters were challenged with jet fuel vapor from fuel tanks of a C-130H and several commercially available LEL span gases. The three detection technologies were infrared, photoionization, and catalytic bead. All meters were calibrated in accordance with manufacturer specifications and with manufacturer-supplied calibration gas. All meters were used as provided by the manufacturers except 0.25-inch (ID) Teflon-lined Tygon tubing was used in lieu of manufacturer-supplied tubing. A Foxboro TVA 1000B, with flame-ionization detector (FID), was used to measure total hydrocarbon content of the jet fuel vapor. Overall, the FID was most sensitive; the photoionization detectors and infrared detector were second. The catalytic beads appeared bifurcated - some were responsive and some were not to vapor compositions after ventilation. After ventilation, the jet fuel vapor composition changes from a C4-C8 dominated vapor to a C9-C12 dominated vapor. Potentially explosive or unsafe environments might go undetected because the traditional catalytic bead sensors cannot ignite the complete vapor mixture. Thus, some LEL meters may significantly underestimate the explosive potential of jet fuel vapor after the light-end of jet fuel has been removed. A second major finding of this study was that manufacturer-recommended calibration techniques do not appear to match instrument performance to jet fuel vapor.

Military-personnel; Confined-spaces; Regulations; Oxygen-deficient-atmospheres; Flammable-gases; Vapor-detectors; Vapors; Gas-detectors; Air-contamination; Testing-equipment; Materials-testing; Toxic-gases; Toxic-vapors; Atmosphere-analyzers; Aircraft; Jet-engine-fuels; Fire-resistant-materials; Fire-retardants; Exposure-assessment; Exposure-levels; Exposure-limits; Fuels; Hydrocarbons; Flame-ionization-methods; Vapor-detectors; Ventilation; Explosion-prevention; Explosive-atmospheres; Explosive-gases; Explosive-hazards; Analytical-instruments

20000520

Abstract

2000

DRDS; PRL

American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida

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