Table 3. Airborne asbestos fiber data from field tests   Airborne fiber concn, fibers/mL Spray test no. NIOSH method7400a,b NIOSH method 7402a,c High Low Mean High Low Mean 10 0.0082 0.0004 0.0022 0 0 0 11 0.0159 0.0033 0.0076 0 0 0 12 0.0204 0.0016 0.0067     0.006 0      0.0015 22 0.007 0.00   0.0028 d d d 26 0.053 0.00   0.022 d d d a The U.S. Occupational Safety and Health Administration permissible exposure level (PEL) is 0.1 fiber/mL. Ref 33. b Personal monitoring; fibers were examined by using phase-contrast microscopy, and results are expressed as an 8-h time-weighted average. c Area monitoring; fibers were examined by using transmission electron microscopy. d These concentrations were not measured. Return to article