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 1,2-DICHLOROTETRAFLUOROETHANE: METHOD 1018, Issue 2, dated 15 August 1994, Page 3 of 4 determined to be appropriate for all three compounds. Dichlorodifluoromethane: Method S111 was issued September 30, 1976 [2], and validated using test atmospheres generated in air and monitored with a calibrated total hydrocarbon analyzer [1,5]. Average recovery for 18 samples was 98.2%. In breakthrough tests at 12 and 94% relative humidity (RH), the capacity of the sampler was 61 and 44 mg of dichlorodifluoromethane, respectively, when sampling at ca. 0.045 L/min from atmospheres containing ca. 10,000 mg/m 3. Desorption efficiency averaged 0.97 in the range 7.4 to 30 mg per sample. Dichlorotetrafluoroethane: Method S108 was issued October 29, 1976 [2], and validated using test atmospheres generated in air and monitored with a calibrated total hydrocarbon analyzer [1,4]. The average recovery for 18 samples was 99.8%. Breakthrough (effluent concentration = 5% of test concentration) occurred after 158 min when sampling 14,600 mg/m 3 at 90% RH at 0.046 L/min. Desorption efficiency averaged 0.99 in the range 10.7 to 42.8 mg per sample. The precision and accuracy of the method for chlorodifluoromethane were determined using test gas bag atmospheres generated and monitored with a halide meter. Average recovery for 18 samples over the range of 1780 to 6970 mg/ m 3 was 100 %. In breakthrough tests at 80% relative humidity, the sampler retained 15.4 mg of chlorodifluoromethane when sampling at 0.025 L/min from atmospheres containing 7000 mg/m 3. The desorption efficiency of chlorodifluoromethane from activated charcoal averaged 0.96 in the range of 0.53 to 10.4 mg per sample.

REFERENCES: [1] Backup Data Reports S111 (Dichlorodifluoromethane) and S108 (Dichlorotetrafluoroethane), prepared under NIOSH Contract 210-76-0123, available as "Ten NIOSH Analytical Methods, Set 1," Order No. PB 271-712, from NTIS, Springfield, VA 22161. [2] NIOSH Manual of Analytical Methods, 2nd ed., Vol. 2, S111 and S108, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-B (1977). [3] Seymour, M.J., M.F. Lucas. Evaluation of Sampling and Analytical Methods for the Determination of Chlorodifluoromethane in Air, Am. Ind. Hyg. Assoc. J., (accepted for publication July 1992) [4] NIOSH Current Intelligence Bulletin 46, U.S. Department of Health and Human Services, Publ. (NIOSH) 86-114 (1986). [5] NIOSH Research Report-Development and Validation of Methods for Sampling and Analysis of Workplace Toxic Substances, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-133 (1980).

METHOD REVISED BY: M.J. Seymour, NIOSH/DPSE.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94