[A comparative study on sampling methods of disposable dust masks for fit tests (2)]

Currently, under the JIS standards, the test guides commonly used in Japan to evaluate the fit of mask facepieces on a wearer's face are not approved for use in fit tests. This study aimed to determine whether a non-destructive test guide for assessing fit could be applied to fit testing using the Japanese Industrial Standards (JIS) Quantitative Fit Test Short Protocol with light-scattering-based measuring devices.

Values obtained using probe attachments approved under the JIS standards were used as reference values, and the fit factor (FF) values measured using test guides and disposable test guides were compared. The evaluation criteria were based on the judgment specified in Annex A2 of the ANSI Z88.10-2010 standards.

The FF values obtained with both test guides and the disposable test guides met the mandatory and additional criteria when compared to those obtained with probe attachments. This indicates that both guides are equivalent to probe attachments for determining pass/fail outcomes and are thus applicable to fit tests. Additionally, the exclusion range, defined to account for device variability, was calculated as FF values ranging from 72 to 138, resulting in the exclusion of approximately 11% of the data from the evaluation. This exclusion range was deemed appropriate, as the effective data rate closely matched the pass/fail consistency rate between the two devices. Furthermore, the pass/fail consistency rate between the probe attachments and both guides was approximately 80%. FF values tend to be lower with test guides owing to larger movement during testing than those with probe attachments; however, our results suggest that such differences do not significantly affect pass/fail outcomes. Therefore, the 80% pass/fail consistency rate was not attributed to motion effects but rather reflected the stringent evaluation capabilities of the test guides themselves.

The validity of the fit test using light-scattering based measuring devices under the JIS short protocol was evaluated for disposable masks using test guides that are widely used in Japan to assess the fit between mask facepieces and faces. The results, based on the ANSI criteria, indicated that both the test guides and disposable test guides provided evaluations equivalent to those of the probe attachments. Consequently, this study demonstrated that the test guides and disposable test guides are applicable fit tests. Both test guides concluded that strict evaluations of insertion leakage helped reduce false positives, making them reliable for worker protection.