National Institute for Occupational Safety and Health

“ Process three blank filters through the extraction and measurement procedures.
MEASUREMENT: 9. 10.
11.
Transfer via pipet a 1.0-mL aliquot of sample extract to a preweighed weighing cup. Place weighing cup in vacuum oven preheated to 40 °C. Apply vacuum until pressure in the oven is 7 to 27 kPa (50 to 200 mm Hg) . Allow solvent to evaporate for 2 hrs. Release vacuum by slowly opening release valve which has an in-line filter to remove room dust. Equilibrate the weighing cup to the temperature and relative humidity of the balance room for at least 30 min. ”

“ Several benzene extracts of samples of aluminum reduction plant emissions were combined to give a solution containing 1.35 mg of benzene-soluble material per sample; nine aliquots of this solution gave residue weights with a relative standard deviation of 0.02. Benzene extracts of six blank filters gave residue weights with a relative standard deviation of 0.23 [6] . ”

“ Occupational Exposure to Coal Tar Products, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-107 (1978) . [3] Criteria for a Recommended Standard ... Occupational Exposure to Coke Oven Emissions, U.S. Department of Health, Education, and Welfare, Publ. ”