Assessment of the Particle Filtration Efficiency of N95 Masks Protecting Quarry Workers in Erongo, Otjozondjupa, and Kunene Regions of Namibia DOI: https://dx.doi.org/10.4314/ajhs.v38i1.5

Abstract

Background: Quarry workers use different types of N95 masks to protect themselves from occupational respirable dust. However, little is known about the filtration efficiency of N95 masks among Namibian quarry workers. Hence, this study measured the filtration efficiency of the different N95 masks used in quarry mines following respirable dust exposure.

Methodology: The study employed a quantitative experimental design in a controlled environment with a sample of seven (7) N95 masks labelled A, B, C, D, E, F, and G from seven (7) quarry mining sites, with one mask from each site. Samples were selected using purposive sampling, focusing on the availability of masks FFP1 and FFP2, which are considered standard respiratory protection masks used in quarry mines. Masks' particle filtration efficiency and effectiveness were assessed by an experiment that included gravimetric weighing, mask testing, and particle size analysis techniques.

Results: The seven N95 masks collected insignificant dust compared to the amount of dust that passed through them, through gravimetric weighing. Site G recorded the highest dust exposure at 0.015mg, above the technique's standard uncertainty of ±0.010mg. Sites A and B had lower filtered dust weights, whereas Sites C, D, F, and G had higher values. The mass on filters increased significantly with a 5-minute sample period. The particle size analyser method showed that Sites A, B, and C showed smaller particles with 100% of the PM10 range, while sample Site D showed the highest particle size, with at least 60% below the PM10 range.

Conclusions: The N95 mask efficiently filters respirable dust particles at the initial stages. However, their filtration efficiency diminishes following prolonged use. Accordingly, Efficacy decreases as respirable dust exposure increases.

Recommendations: Based on the study findings, all the N95 masks met the filtration efficiency standards that attain the ideal respiratory protection; therefore, quarry workers should just increase the frequency of changing the masks. Additionally, masks should be tested upon fitting, properly fitted when used, and frequently replaced to complement the desired filtration efficiency.