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Assessing internal noise levels in powered air purifying respirators using standardized manikin sizes in a laboratory
Ikenna Orji1, Cheryl Beseler1, Brian Maass2
1Department of Environmental Agricultural and Occupational Health, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska.
Abstract:
Powered air-purifying respirators (PAPRs) generate internal noise from the blower and result in turbulent airflow. Internal noise may reduce speech clarity and increase listening effort during critical tasks. This study examined how PAPR brand and user configuration factors affected internal noise levels. A total of 1,200 internal PAPR noise measurements were recorded on a manikin across multiple experimental conditions: two PAPR brands, five manikin sizes, hair or shroud attached (Yes/No), and both hair and shroud attached. The generalized linear mixed model with a rank-based nonparametric test was used to analyze the bivariate association between variables, given the abnormal distribution of the mean noise data. The use of the active 3M PAPR on a small manikin produced the highest mean noise level [70.7 dBA; 95% confidence interval (CI): 70.31 to 71.16] at baseline (i.e., without hair or shroud), while use on a medium manikin had the lowest (57.3 dBA; CI: 56.87 to 57.72). The 3M PAPR was significantly louder (Mean difference: 4.1 dBA; CI: 3.44 to 4.72) than the MAXAIR at baseline, though after adjusting for PAPR brand and manikin size, and considering hair and shroud individually, MAXAIR was slightly but significantly louder (Mean difference: 0.5 dBA; CI: 0.20 to 0. 90). The presence of hair was associated with a significant reduction (Mean reduction: 2.31 dBA; CI: 0. 98 to 3.65) in internal noise levels after adjusting for PAPR brand and manikin. Use of a shroud alone had a small, nonsignificant effect (Mean difference: 0.78 dBA; CI: -0.55 to 2.11) on noise levels. However, the combined effect of hair and a shroud, when comparing "Both vs. None," resulted in a lower noise level (Mean difference: 3.08 dBA; CI: -0.01 to 6.17), although this reduction was not statistically significant (p = 0.101). These findings suggest the need to focus on blower and airflow design, along with considering acoustic dampening near the ears, to improve communication during use.
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