Water-blocking Asphyxia of N95 Medical Respirator During Hot
Environment Work Tasks With Whole-body Enclosed Anti-bioaerosol
Suit

Water-blocking Asphyxia of N95 Medical Respirator During Hot
Environment Work Tasks With Whole-body Enclosed Anti-bioaerosol
Suit

Aerosolized particles and droplets
Airflow obstruction
Hot temperature
N95 respirators
Protective clothing

During hot environment work tasks with whole-body enclosed anti-bioaerosol suit, the
combined effect of heavy sweating and exhaled hot humid air may cause the N95 medical respirator to
saturate with water/sweat (i.e., water-blocking).
Methods: 32 young male subjects with different body mass indexes (BMI) in whole-body protection (N95
medical respirator þ one-piece protective suit þ head covering þ protective face screen þ gloves þ shoe
covers) were asked to simulate waste collecting from each isolated room in a seven-story building at 27-
28C, and the weight, inhalation resistance (Rf), and aerosol penetration of the respirator before worn
and after water-blocking were analyzed.
Results: All subjects reported water-blocking asphyxia of the N95 respirators within 36-67 min of the
task. When water-blocking occurred, the Rf and 10-200 nm total aerosol penetration (Pt) of the respirators reached up to 1270-1810 Pa and 17.3-23.3%, respectively, which were 10 and 8 times of that before
wearing. The most penetration particle size of the respirators increased from 49-65 nm before worn to
115-154 nm under water-blocking condition, and the corresponding maximum size-dependent aerosol
penetration increased from 2.5-3.5% to 20-27%. With the increase of BMI, the water-blocking occurrence
time firstly increased then reduced, while the Rf, Pt, and absorbed water all increased significantly.
Conclusions: This study reveals respirator water-blocking and its serious negative impacts on respiratory
protection. When performing moderate-to-high-load tasks with whole-body protection in a hot environment, it is recommended that respirator be replaced with a new one at least every hour to avoid
water-blocking asphyxia.

Jintuo Zhu 1,2,3
, Qijun Jiang 1,2,3
, Yuxuan Ye 1,2,3
, Xinjian He 1,2,3,
*, Jiang Shao 4
, Xinyu Li 1,2,3
,
Xijie Zhao 4
, Huan Xu 5
, Qi Hu 1,2,3

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1 Key Laboratory of Gas and Fire Control for Coal Mines (China University of Mining and Technology), Ministry of Education, Xuzhou, Jiangsu, China
2National Professional Laboratory for Fundamental Research of Mine Gas and Dust Control Technology, School of Safety Engineering, China University of
Mining and Technology, Xuzhou, Jiangsu, China
3 School of Safety Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, China
4 School of Architecture & Design, China University of Mining and Technology, Xuzhou, Jiangsu, China
5 School of Materials Science and Physics, China University of Mining and Technology, Xuzhou, Jiangsu, China

21 October 2023

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