US EPA

3655401 

Technical Report 

Evaluation of Respirator Filters for Asbestos Fibers 

Cheng, YS; Fan, B; Holmes, TD; Yeh, HC 

1996 

NIOSH/00231889 

Inhalation Toxicology Research Institute 

R01-OH-02922 

The effects of fiber dimensions, flow rate, and charge status of filter cartridges on the penetration of fiber aerosols were examined, using four types of test respirator filters (two for passive respirators, one for a powered respirator, and one disposal respirator). Some filters were charged to enhance the collection efficiency. Only high efficiency filters performed consistently for both spherical test aerosols and the three types of asbestos (1332214) fibers. The performance of these filters did not appear to be changed by the surface charge potential of filter cartridges and charge status of fibers. When the change potential on the filter was removed and/or fiber aerosols discharged, the performance of low efficiency filters and masks deteriorated for aerosols. The surface charges decreased in a high temperature, high humidity environment and disappeared after 1 week. Shorter fibers had higher penetration rates, indicating that fiber interception is an important deposition mechanism. The maximum fiber penetration occurred in the region of fiber diameter and length where the interception diffusion deposition were at a minimum. These fibers could penetrate the face mask seal, with increased penetration for larger leaks. The fibers that penetrated had sizes similar in distribution to those found in bulk aerosols and may be a major concern for respiratory protection.