The ability of a specific method from the Manual of Analytical Methods of NIOSH to determine chlorodifluoromethane (75456) in workplace air was studied. The method under study was Method 1020, which was recommended by OSHA for this determination. As Method 1020 was developed originally for detection of a liquid, and the current recommendation was to use the method for determination of a gas, this proposed use was tested by NIOSH. The tests indicated that the capacity of the 100/50 milligram (mg) charcoal sorbent bed was limited, the standard preparation procedure was incorrect for a gas analyte, and the analyte had low solubility in carbon-disulfide. Method 1018 for dichlorodifluoromethane (75718) used two coconut shell charcoal tubes in series, a 400/200mg tube followed by a 100/50mg tube, desorbed with methylene-chloride. Test atmospheres for 0.5 to two times the permissible exposure limit for chlorodifluoromethane were generated for the study. Changes were made in the standard preparation procedure and the gas chromatograph was equipped with a capillary column to make the method more suitable for this purpose. By making these revisions to the method, a 96.5% recovery was obtained along with a total precision for the method of 7.1% for chlorodifluoromethane. The method presented no significant bias. The authors conclude that the revised Method 1018 is suitable for determining chlorodifluoromethane in workplace air.