Field study of subjective assessment of negative pressure half-masks. Influence of the work conditions on comfort and efficiency.

The aim of this study was to assess the effects of work conditions on the acceptability and efficiency of respiratory protective devices (RPD). The subjective evaluation of comfort, protection, respiratory and visual constraint, and the acceptable duration of wear of six RPDs against dust was achieved by 30 workers during their actual work. Metabolic rate was evaluated for each worker, and dry and wet air temperatures measured in the work area. RPDs objective protection factor was measured during each of the 180 test periods. In the conditions of this study, the acceptable duration of wear was about 1 h. This duration and the comfort parameters were reduced when the air temperature increased. The younger workers and/or smokers were less sensitive to mask discomfort. Objective protection factors of the RPDs are reduced under warmer conditions, and when the metabolic rate is low. Finally, the results of this study also show the poor capacity of standardized leakage tests to assess the objective respiratory protection of workers in the field. Some hypotheses which can explain this fact are discussed.