Introduction: Preventing healthcare professionals from acquiring occupational infectious diseases is very important in maintaining healthcare delivery systems. For protection in the work place, healthcare professionals use PPE which helps prevent exposure to pathogens during patient care. N95 respirators protect healthcare workers against airborne pathogens that are known to be associated with different respiratory diseases. Since previous studies have shown that viruses can survive on PPE surfaces, it is important to examine the survival of viruses on respirators to determine if reuse of the same N95 respirator is possible when PPE shortages occur. Goal: The goal of this research is to determine the inactivation of bacteriophage Φ6 on the surface of N95 respirators at ambient temperature and two different relative humidity levels, 40 and 60%. Result: The linear regression showed that rate of inactivation was much lower in 40% than 60% RH (40%: Slope= -0.046± 0.007040; 60%: Slope= -0.20± 0.006136). Over 24 hours, there was a ~1 Log10 reduction in virus at 20°C and 40% RH, while there was a ~4 Log10 reduction at 20°C and 60% RH. Within the timeframe of a single patient encounter, there was a <0.02 Log10 reduction in virus at 40% RH and a <0.1 Log10 reduction at 60% RH. Conclusion: Bacteriophage Φ6 survives on N95 respirators for up to 24 hours at ambient temperature and 40 and 60% relative humidity levels. Inactivation rate was lower in 40% than 60% RH. The results showed that enveloped viruses survive on the surface of N95 respirators for longer than a single patient encounter. Therefore, this should be taken into consideration when doing a risk assessment of reusing N95 respirators when shortages occur.

The emergence of nanotechnology has increased the concern of exposure to nanoparticles through inhalation. Studies have examined the performance of filtering facepiece respirators against engineered nanoparticles. This has been done by the generation and dispersal of certain particles in a given size distribution, which have then been run through experimental set-ups involving Condensation Particle Counters, Scanning Mobility Particle Sizers, and high efficiency performance filters for a set flow. Published studies have shown that the respirators used do provide expected levels of filtration protection against nanometer-sized particles. However, studies have not examined or applied different types of nanoparticle samples - different particle types have differing morphologies and physical characteristics that could affect filter performance. This study has exposed NIOSH-approved N95 facepiece respirators to six different types of engineered nanoparticles: aluminum oxide, iron oxide, single-walled carbon nanotubes, synthesized diamond, silicon dioxide, and titanium dioxide. In addition, N95 respirators have not been commonly exposed to differing concentrations of an aerosol in order to observe a shift in the primary penetrating particle size and a shift in the overall size distribution. This study challenged N95 respirators to four different concentrations of sodium chloride: 0.1, 1, 10, and 50 mg/ml. Another concern is whether or not a prolonged exposure of a single respirator affects the overall performance and protection from an aerosol, especially engineered nanoparticles, since very few studies have been done regarding this matter. N95 respirators were exposed to several types of engineered nanoparticles in a respirator testing apparatus at a set flow rate, examined for penetration with an SMPS, CPC, and DMA given these conditions: differing concentrations of sodium chloride, different engineered particles, and an extended duration of exposure to both sodium chloride and 15-nm titanium dioxide. This study showed that the primary penetrating particle size through an N95 facepiece respirator does increase and shift with increasing concentrations of an aerosol; however, the overall size distribution did not seem to shift much. Penetration decreased as sodium chloride concentration increased. Different nanoparticles had differing primary penetrating particle sizes through the respirator; however, penetration of these particles was similar to one another with the exception of iron oxide which had quite a high penetration percentage. A decrease in N95 respirator performance was observed when exposed to a 1 mg/ml solution of sodium chloride, as penetration increased with prolonged exposure. However, this did not seem to be the case when the respirator was exposed to a 6.67 mg/ml suspension of 15-nm titanium dioxide, as the penetration over the extended period of time was similar to one another.

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