P-486 EFFECTS OF INTERNAL FACEPIECE PRESSURE SETTINGS TRIGGERING THE FAN OPERATION OF POWERED AIR PURIFYING RESPIRATORS (PART 1)—EFFECTS ON THE INTRA-FACEPIECE CARBON DIOXIDE CONCENTRATION

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Introduction</jats:title> <jats:p>Our previous study found that commercial powered air-purifying respirators (PAPRs) effectively protected against particles but retained high levels of exhaled carbon dioxide (CO2) gas within the facepieces. This study investigates the effects of internal facepiece pressure settings, which trigger the fan operation of PAPRs, on the intra-facepiece CO2 concentration.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Twelve healthy, non-smoking men participated in the study. Three types of breath-responsive PAPR were used: PAPR-A, having a higher pressure setting than a commercial model; PAPR-B, a commercial model; and PAPR-C, having non-fan operation. To mitigate order effects and exercise-induced fatigue, participants were randomly assigned to six groups. Participants wore each PAPR and exercised for 10 minutes at 40% of their maximal oxygen uptake while the intra-facepiece gas concentration was measured. This study was approved by the Ethics Committee of the University of Occupational and Environmental Health, Japan.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>During inhalation, the intra-facepiece CO2 concentration decreased in the order of PAPR-C, PAPR-B, and PAPR-A, with the mean values for each individual ranging 2.1%–5.0%, 1.6%–4.0%, and 1.6%–3.1%, respectively.</jats:p> </jats:sec> <jats:sec> <jats:title>Discussion</jats:title> <jats:p>Increasing the internal facepiece pressure setting improved the intra-facepiece air quality. This improvement is attributed to the longer fan operation, which increased the air supply and enhanced ventilation within the facepiece. However, a disadvantage of a higher pressure setting was a shorter operating time of the battery powering the fan.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>A higher internal facepiece pressure setting was found to be effective in maintaining an appropriate intra-facepiece CO2 concentration compared with a commercial model. The development of smaller longer-lasting batteries is expected.</jats:p> </jats:sec>