National Institute for Occupational Safety and Health

“ Use serial dilutions as needed to obtain trifluorobromomethane concentrations in the range 0.01 to 3.6 mg/mL. b. Analyze with samples and blanks (steps 11 and 12) . c. Prepare calibration graph (peak area vs. mg trifluorobromomethane) . 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. Connect a large charcoal tube (400 mg/200 mg) to the outlet of the DE apparatus. Start nitrogen flow (ca. 200 mL/min) through the DE apparatus and into the charcoal tube. ”

“ Glass tubing, through which nitrogen flows at ca. 200 mL/min, with T-connection and septum. Wrap outlet of tubing with heating tape and connect tubing to inlet of test sampler.
SPECIAL PRECAUTIONS: Methylene chloride is a suspect carcinogen and is metabolized to carbon monoxide, a toxic gas [3] .
SAMPLING: 1. 2. 3. 4.
Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler tubes immediately before sampling. Attach sampler to personal sampling pump with flexible tubing with the smaller tube nearer the sampling pump. ”

“ A silylated glass wool plug precedes each front section and a 3-mm urethane foam plug follows each back section. Pressure drop across the tubes at 1 L/min airflow must be less than 3.4 kPa. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 0.05 L/min, with flexible connecting tubing. ”