National Institute for Occupational Safety and Health

“ The capacity of the charcoal is greatly reduced when sampling in high humidity [4] .
OTHER METHODS:This revises NMAM 1005 (dated 8/15/94) [5] . If sampling in an atmosphere with high relative humidity ( 80%) , a tube with larger bed of charcoal is recommended. OSHA Method 59 uses a sampler with three sorbent sections, each containing 350 mg of charcoal, and has been evaluated for a 10-L air sample at 1 ppm of methylene chloride with 80% relative humidity [4] . OSHA Method 80 uses a carbon molecular sieve sampler and GC-FID analysis, and has been evaluated at 10 ppm and 500 ppm [6] . ”

“ Significant heat is generated when the desorbing solution is added to the charcoal. To minimize sample loss, chill the desorbing solution before adding to the charcoal [4] . 7. Allow to stand 30 min with occasional agitation to aid desorption.
CALIBRATION AND QUALITY CONTROL: 8. Calibrate daily with at least six working standards over the range of interest. Three standards (in duplicate) should cover the range from the LOD to LOQ. a. Add known amounts of methylene chloride to CS 2 in 10-mL volumetric flasks and dilute to the mark. ”

“ Carbon disulfide is toxic and a serious fire and explosion hazard (flash point = -30 C) . Methylene chloride is a suspected carcinogen. Wear appropriate protective clothing and work with these compounds in a well ventilated hood.
SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break ends of sampling tubes immediately before sampling. Attach sampler train to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate between 0.01 and 0.2 L/min for total a sample size of 0.5 to 2.5 L. 4. ”