National Institute for Occupational Safety and Health

“ Prepare calibration graph (peak area vs. mg methyl chloride) . Determine desorption efficiency (DE) at least once for each lot of sorbent used for sampling in the range of interest. Prepare three tubes at each of five levels plus three media blanks. a. Using a gas-tight syringe, slowly inject a known amount of methyl chloride (0.005 to 0.5 mL) through the septum of the DE apparatus into a stream of nitrogen which carries the analyte into a large (400 mg/200 mg) sorbent tube. Allow the nitrogen to flow an additional 1 min. b. Cap the tube. Allow to stand overnight. ”

“ Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing, with the smaller tube nearer the sampling pump. Sample at an accurately known flow rate between 0.01 and 0.1 L/min for a total sample size of 0.4 to 3 L (e.g., at 0.1 L/min for 15 min for STEL measurement and 0.01 L/min for 50 to 300 min for TWA measurement) . ”

“ Breakthrough (effluent = 5% of test concentration) occurred after sampling for 135 min at 0.0235 L/min from an atmosphere containing 410 mg/m 3 methyl chloride in air at 80% RH, and at 24.4 NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition, 8/15/94 METHYL CHLORIDE: METHOD 1001, Issue 2, dated 15 August 1994 - Page 4 of 4 min when sampling at 0.105 L/min from an atmosphere containing 1425 mg/m 3 at 84% RH. Desorption efficiency for 18 samples in the range 0.16 to 0.62 mg methyl chloride averaged 0.99 with s r = 0.02. ”