This study was conducted to investigate the protection of disposable filtering half-facepiece respirators of different grades against particles between 0.093 and 1.61 μm. A personal sampling system was used to particle size-selectively assess the protection of respirators. The results show that about 10.9% of FFP2 respirators and 28.2% of FFP3 respirators demonstrate assigned protection factors (APFs) below 10 and 20, which are the levels assigned for these respirators by the British Standard. On average, the protection factors of FFP respirators were 11.5 to 15.9 times greater than those of surgical masks. The minimum protection factors (PFs) were observed for particles between 0.263 and 0.384 μm. No significant difference in PF results was found among FFP respirator categories and particle size. A strong association between fit factors and protection factors was found. The study indicates that FFP respirators may not achieve the expected protection level and the APFs may need to be revised for these classes of respirators.

Full facepiece respirators (FFRs) with charcoal cartridges are very common wearable devices for industrial or military purposes preventing respiratory tract, face, eyes, and mouth from hazards exposure. However, related research for performance evaluation was rare. We aimed to use a self-developed testing system investigating (1) filtration efficiency (FE) of aerosols in charcoal cartridges; (2) breakthrough time of cyclohexane in charcoal cartridges; (3) fit factors (FFs) and (4) protection factors (PFs) of FRRs. The results showed that FE of charcoal cartridges against 0.3 µm of sodium chloride (NaCl) and dioctyl phthalate (DOP) particles under 85 L min -1 were 99.93% and 99.89%, respectively, which did not meet the standard 99.97% regulated for filters such as P100 and HEPA. As for 42.5 L min -1 condition (dual canisters), the FE against NaCl (99.97%) did meet the requirement set for HEPA (99.97%); however, that against DOP (99.95%) failed to meet the standard. In addition, the breakthrough time of 3000ppm cyclohexane was 31 min under 32 L min -1 , which was longer than the 30 min standard described in CNS6636 Z2023 and JIS8152. As to the results of fit test among 21 subjects, only 1 failed to meet the requirement (fit factor = 500) and the average of fit factors was 8342 ± 5892. The mean value of protection factors was 112.3 ± 54.6 while 3 users had lower PFs than the assigned protection factor (APF = 50) regulated by Occupational Safety and Health Administration (OSHA). APFs obtained for particles less than 100 nm were smaller than the APF standard regulated by OSHA, indicating APF standards may be overestimated for such particle size. Therefore, users should be aware of potential risks caused by such substances in nano-sized scale (e.g., nanoparticles or viruses) when wearing FFRs.

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A simple film theory model yielding a closed-form solution is presented for the analysis of isothermal gas absorption with a chemical reaction taking into account the effect of interfacial resistance. The analysis could be particularly important for a rational design of wet scrubbing systems for gaseous pollutant removal with impurities contaminating the gas-liquid interface. The film theory avoids time dependence and thus is much easier to apply than the penetration theory. The results obtained by the two different theories are in good agreement.