Introduction Inhalation resistance of respirators may induce additional burden for workers breathing. Powered air-purifying respirators (PAPR) are considered to reduce this burden by assisting inhalation with powered fan. While there are mainly two types of blower system; breath response type and constant air flow type, no study has been conducted to clarify the difference of their physiological effects as far as we searched. We conducted this study to elucidate the physiological effects of wearing different types of PAPR by measuring physiological parameters and the microclimate inside the PAPRs.

Methods Eight healthy males participated in the study. They took a 40 minutes-exercise with ergometer at 20, 30, 40% and 50% VO₂max while wearing three types of masks;

• half mask facepiece with breath response type (BR–PAPR),

• half mask facepiece with constant air flow type (CF–PAPR) and

• mask of expiration gas analyzer (control).

We continuously measured their auditory canal temperature (t _ac), heart rate (HR) and SpO₂. We also measured the microclimates (temperature, humidity, O₂, CO₂) inside the two PAPRs. Their subjective symptoms were also surveyed. Statistical analysis was performed by IBM SPSS Statistics22.0.

Result There were few differences in the trend of t _ac, HR and SpO₂ among the masks. SpO₂ gradually declined but remained within normal level. The temperature and humidity inside masks were higher in BR-PAPR. During inhalation period, the proportion of time which O₂ concentration became lower than 18% or which CO₂ concentration exceeds 3% inside the respirators were lower in CF-PAPR. The participants’ perception of hotness or humidity coincided with the microclimates.

Discussion BR-PAPR is known for the better durability of battery compared with CF-PAPR. There were few differences in physiological parameters among those respirators. However, with respect to the microclimate inside respirators, CF-PAPR was better than the BR-PAPR, hence it may affect comfort of the workers.