The Effect of Soil Accumulation on Multiple Decontamination Processing of N95 Filtering Facepiece Respirator Coupons Using Physical Methods
Edward M. Fisher, Jessica Williams, and Ronald E. Shaffer
The supply of filtering facepiece respirators (FFRs) may not be adequate to match demand during a pandemic. One possible strategy that has been identified is to reuse the FFR after application of a decontamination method to remove infectious material contaminating the FFR. One of the factors affecting decontamination in real world application is soil load (accumulated residues such as cells, cell debris and proteins), which can inhibit the effectiveness of the decontamination method. The objective of
this study was to assess the effect of soil load on repeated decontamination of FFR coupons using energetic methods; microwave-generated steam and ultraviolet germicidal irradiation (UVGI). MS2 bacteriophage, suspended in media containing soil loads, was aerosolized and applied to FFR coupons. The coupons were cyclically contaminated and then treated with microwave-generated steam or UVGI for three series. The effect of soil load was evaluated by measuring decontamination efficacy, residual protein concentration, and UVGI penetration into the contaminated coupons. Soil load, measured as protein concentration, increased with each successive cycle of contamination. Microwave-generated steam decontamination efficacy was similar for all three cycles regardless of the soil accumulation (p = 0.34). UVGI decontamination demonstrated a difference in efficacy among the cycles of both the low and high soil load sample sets (p < 0.01). UVGI penetration into the FFR generally decreased with an increase in soil load but demonstrated a linear correlation with decontamination efficacy (R2 = 0.88). Steam treatment of FFRs may be a viable decontamination technique for multiple cycle treatments, given the lack of effect of the soil load on virus inactivation efficacy. Soil load has the potential to lessen the efficacy of UVGI, but this effect can be mitigated by measuring the decrease in UVGI irradiance and compensating with increased UVGI exposure time.
Keywords: filtering facepiece respirator, N95, reuse, decontamination, UVGI, steam