Comparison of six respirator fit test methods with an actual measurement of exposure in a simulated health care environment: Part II - Method comparison testing

This article, the second in a series of three, describes the method comparison testing portion of a study conducted to compare the fit factors from six quantitative fit-tests (QNFT) with a measure of a respirator wearer's actual exposure assessed by end-exhaled air analysis for 1,1,2-trichloro-1,2,2-trifluoroethane (Freon-113) under the same conditions. The six QNFT methods were (1) continuous low flow, flush probe; (2) continuous high flow, deep probe (CHD); (3) exhalation valve discharge (EVD); (4) controlled negative pressure; (5) 10-minute Ambient Aerosol 1 (AA1); and (6) 30-minute Ambient Aerosol 2. The first three methods utilized corn oil and a forward light scattering photometer. The last two methods used the TSI Portacount. Respirators used in the study were both disposable and elastomeric organic vapor/ high efficiency half-masks. The characterization equations from the preliminary research (described previously) were used to determine the actual exposure to Freon-113 during the method comparison testing. The fit factors resulting from the QNFT methods were then individually correlated with the Freon-113 exposures using the coefficient of determination, R-2. The lowest R-2 value, 0.20, was found with the EVD method. The highest R-2 values, 0.81 and 0.78, were associated, respectively, with the CHD and AA1 methods. This study suggests that some QNFT methods may be used to estimate actual respirator performance under laboratory conditions.