The effect of N95 designs on respirator fit and its associations with gender and facial dimensions.

This study examined the association of various brands of NIOSH-certified N95 filtering face-piece respirators (FFR) fit with facial dimensions and gender. One hundred and thirty-five participants (77 females and 58 males) were recruited from the previous facial anthropometry study among Malaysians in 2020. Quantitative respirator fit testing of six FFR were performed using the TSI Portacount Pro+ 8038 which comprised of four exercises (bending over, talking, up-down head movement, and side to side head movement). An overall fit factor (FF) of ≥ 100 was considered a pass for each FFR. Analysis was done using T-test, Pearson's correlations, and generalised linear regression. The passing rates for the six FFR were 36.3% (Cup B), 50.4% (Trifold A), 54.1% (Duckbill A), 57.0% (Cup A), 74.1% (Trifold B), and 83.7% (Duckbill B). Both Duckbill B and Trifold B had the highest passing rates for both genders. However, certain FFR models (Cup B, Trifold A, Trifold B, and Duckbill A) fit better for participants with large facial size who were mostly males, while others (Cup A and Duckbill B) specifically fit better for those with small facial size, who were mostly females. This study showed significant positive effect of nose protrusion, nasal root and subnasale-sellion and the negative effect of menton-sellion, bigonial breadth and nose breadth on fit factors of various FFR. The results of this study emphasized the importance of choosing and designing FFR based on local anthropometry data, with careful consideration on the dimensions that affect the respirator fit. Since N95 are commonly used in the healthcare settings to prevent airborne transmission, the practice of respirator fit testing and selecting N95 with high passing rates for healthcare workers need to be emphasized.

Effect of UV-C germicidal irradiation (UVGI) on the structural integrity of N95 and KN95 respirators.

This study focuses on reprocessing a group of filtering facepiece respirators (FFR) using ultraviolet germicidal irradiation (UVGI). The aim is to explore the possibility of disinfecting selected KN95 FFRs, in comparison with the N95 FFRs, and assess their viability for reusage. For this purpose, five models of unused N95 and KN95 FFR models obtained from the hospital were exposed to UV-C light using a customized UVGI chamber. The material integrity of treated FFRs was examined in terms of particle penetration and strap tension. The surface morphology of all models is inspected to determine the visible changes of each FFR upon exposure to 1-100 cycles (1 cycle is equivalent to 1 J/cm2 UV dose). The penetration test results indicate that the physical properties of the KN95 and N95 FFRs remain within permissible limits despite being reprocessed by up to 100 cycles (100 J/cm2). Using a microscope, the physical observations also reveal that no visible damage can be seen even after 100 J/cm2 exposure. Apart from the filter bodies, the tension of each strap was also found to not be significantly affected by UV radiation by at least 10 disinfection cycles (10 J/cm2). This confirms that KN95, as well as N95 FFRs, can be subjected to UV treatment as a means of disinfection.

Performance Comparison of Single and Double Masks: Filtration Efficiencies, Breathing Resistance and CO2 Content.

The emergence of a pandemic affecting the respiratory system has resulted in a significant demand for face masks. Masks have always been mentioned as an effective tool against environmental threats. This includes the use of double masks by large sections of the public, as can be seen during the current global spread of COVID-19. However, there is limited knowledge available on the performance of the various commonly available double face masks used. In this study, we have compared the performance of single and double face configurations. Three types of 3-ply face mask (FM), three types of fabric face mask (CM) and nine configurations of these face masks were investigated based on morphology, filtration efficiencies, breathing resistance and carbon dioxide (CO2) content. The filtration efficiencies of the double face masks are enhanced when combined with a fabric mask, and were found to improve by 500% compared to those of a fabric mask. The lowest breathing resistance among the double masking was observed in the combination of FM1 and fabric face masks. From the results, it was found that all combinations of double face mask are suitable to use since the measurements indicate that the breathing resistance and CO2 contents are still lower than the acceptable value set by the Malaysian Standard (MS 2323:2010) and European Standard (EN 149:2001 + A1:2009). The performance of double masks is comparable with that of N95 respirators. The double masking combination can be used as an alternative method to reduce inhalation exposure to airborne contaminants.