Respiratory protective device: One size to fit them all?

Abstract

When exposed to hazardous or toxic substances, workers may be required to wear respiratory protective devices, selected in accordance with the pollutant, required protection level, individual characteristics, and work conditions. To emphasize the importance of the selection procedure, this study aimed to investigate the effects of the facial dimensions and breathing rate on the fit and the protection efficiency provided by full-face respirators. Manikin total efficiency measurements (mTEs) were then conducted on five head forms of various facial dimensions equipped with nine respirators of different models and sizes. A breathing machine simulating sinusoidal breathing rates was used to represent seven work rates, from rest to maximal intensity. For each experiment, the manikin fit factor (mFF), characterizing the respirator fit on the head form, was measured by a controlled negative pressure method. By varying the head form, respirator, breathing rate, and mFF, a total of 485 values of mTE were measured. Findings indicate that even if the respirator was equipped with a high-efficiency filter, mTE strongly decreases if the respirator does not fit the face of the wearer. In particular, it was highlighted that one given respirator cannot fit all facial dimensions and that the best match between the respirator size and facial dimensions is difficult to predict because respirator sizes are not standardized. Moreover, although the total efficiency of a well-fitted respirator naturally decreases when increasing the breathing rate due to filtration mechanisms, the reduction is more significant if the respirator does not fit well. To consider both the mTE and the breathing resistance, a quality factor value was determined for each tested combination of head form, respirator, and breathing rate. The maximum manikin fit factor mFF_max measured for each combination of head form and respirator was compared to that measured on nine human subjects with similar facial dimensions, providing encouraging results concerning the use of head forms during respirator testing.

Keywords:

• Aerosol
• filtration
• fitting
• respirator

Acknowledgments

The authors declare no conflict of interest relating to the material presented in this article. Its contents, including any opinions and/or conclusions expressed, are solely those of the authors.

Data availability statement

All data included in this study are available upon request by contact with the corresponding author.

Additional information

Funding

Funding for this project was entirely based on the core funding of Institut National de Recherche et Sécurité (INRS) which is the sole employer of the authors.