Development of a test system to apply virus-containing particles to filtering facepiece respirators for the evaluation of decontamination procedures

Abstract

A chamber to apply aerosolized virus-containing particles to air-permeable substrates (coupons) was constructed and validated as part of a method to assess the virucidal efficacy of decontamination procedures for filtering facepiece respirators. Coliphage MS2 was used as a surrogate for pathogenic viruses for confirmation of the efficacy of the bioaerosol respirator test system. The distribution of virus applied onto and within the coupons was characterized, and the repeatability of applying a targeted virus load was examined. The average viable virus loaded onto 90 coupons over the course of 5 days was found to be 5.09 +/- 0.19 log(10) PFU/coupon (relative standard deviation, 4%). To determine the ability to differentiate the effectiveness of disinfecting procedures with different levels of performance, sodium hypochlorite and steam treatments were tested in experiments by varying the dose and time, respectively. The role of protective factors was assessed by aerosolizing the virus with various concentrations of the aerosol-generating medium. A sodium hypochlorite (bleach) concentration of 0.6% and steam treatments of 45 s and longer resulted in log reductions (>4 logs) which reached the detection limits for both levels of protective factors. Organic matter (ATCC medium 271) as a protective factor afforded some protection to the virus in the sodium hypochlorite experiments but was not a factor in the steam experiments. The evaluation of the bioaerosol respirator test system demonstrated a repeatable method for applying a targeted viral load onto respirator coupons and provided insight into the properties of aerosols that are of importance to the development of disinfection assays for air-permeable materials.

Figures

FIG. 1.

Schematic diagram of the BARTS.

FIG. 2.

Schematic diagram of the test specimen holder assembly.

FIG. 3.

Effects of a neutralizer on the efficiency of MS2 application to FFR coupons. The symbols indicate the averages and the error bars indicate the standard deviations for four coupons loaded in two experimental runs.

FIG. 4.

Repeatability of the application of MS2 using BARTS. MS2 was loaded onto 90 FFR coupons over a 5-day period. Six coupons were loaded simultaneously during three runs per day. The bars indicate the average for each filter sample port (ports I to VI).

FIG. 5.

Percentage of MS2 deposited on each coupon layer for LPF and HPF suspension media. The error bars indicate standard deviations of four samples.

FIG. 6.

Size distribution of particles generated from the nebulization of suspension media: combined SMPS and APS size distributions for particles as measured at the sample ports for water, LPF medium, and HPF medium. The data were normalized to the peak bin value of the scan for each medium type.

FIG. 7.

Sodium hypochlorite concentration-dependent reduction of MS2 aerosolized in LPF and HPF media. The error bars indicate the standard deviations of three samples. Note that bleach concentrations of 0.006%, 0.06%, and of 0.6% for LPF medium and 0.6% for HPF medium resulted in LRs which reached the detection limits.

FIG. 8.

Steam treatment time-dependent reduction of MS2 aerosolized in LPF and HPF media. The error bars indicate the standard deviations of three samples. Note that steam treatments of 45 s and longer for both LPF and HPF media resulted in LRs which reached the detection limits.