Abstract
Various types of face masks available to the general public are worn for protection against inhalation of dust, pollutants, allergens, and pathogenic organisms. Recent news stories have illustrated the widespread use of face masks for protection against Swine flu (H1N1), Severe Acute Respiratory Distress Syndrome (SARS), Highly Pathogenic Avian Influenza (HPAI) virus outbreaks in Asia, and dust from the collapse of the World Trade Cen- ter. However, the level of protection provided by face masks is unknown. The objective of this study was to determine how efficiently face masks prevent respiratory exposure to potentially harmful aerosols. Three types of commonly available face masks were tested: a surgical mask, a pre-shaped dust mask, and a bandana. An N95 respirator was tested as the positive control.
…with a mass median aerodynamic particle size of 1.6 m. Face mask protective efficiency was calculated as the ratio of mannequin sample probe concentration to reference sample probe concentration. The protective efficiencies were 33.3%, 11.3%, and 6.1% for the surgical, bandana, and dust masks, respectively. The N95 mask protective efficiency was 89.6%. In conclusion, the surgical mask protected the best of the three face masks tested. However, it is important to note that all three masks offer very little protection when compared to the N95, and wearing these face masks may produce a false sense of protection.
Conclusions
Three commonly available face masks—a surgical mask, a pre-shaped mask, and a bandana—were challenged with saline aerosols in concentrations and particle size distributions representing dust storm conditions to determine their protective efficiencies. A N95 respirator was used as the positive control and challenged un- der the same conditions. All three masks performed poorly, with protective efficiencies less than 34% as compared to the N95 respirator that had a protective efficiency of nearly 90%. Possible factors related to the protective efficiencies observed with face masks and the N95 respirator includes the penetration efficiency and particle load characteristics of the fabrication materials. Equally important is the fit of the face mask and respirator. This may account for the less than 95% efficiency observed for the N95.
Protection from dust, allergens, and infectious aerosols with face masks and respirators is dependent on the aerosol concentration of the compound and the infectious or inhaled dose. The results demonstrate that use of these types of face masks may not provide as much protection as desired against inhaled aerosols.
