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. 2011 Jan;110(1):287-95.
doi: 10.1111/j.1365-2672.2010.04881.x. Epub 2010 Nov 4.

A method to determine the available UV-C dose for the decontamination of filtering facepiece respirators

E M Fisher  1 , R E Shaffer
Affiliations

A method to determine the available UV-C dose for the decontamination of filtering facepiece respirators

E M Fisher et al. J Appl Microbiol. 2011 Jan.

Abstract

Aims: To develop a method to assess model-specific parameters for ultraviolet-C (UV-C, 254 nm) decontamination of filtering facepiece respirators (FFRs).

Methods and results: UV-C transmittance was quantified for the distinct composite layers of six N95 FFR models and used to calculate model-specific α-values, the percentage of the surface UV-C irradiance available for the internal filtering medium (IFM). Circular coupons, excised from the FFRs, were exposed to aerosolized particles containing MS2 coliphage and treated with IFM-specific UV-C doses ranging from 38 to 4707 J m(-2). Models exposed to a minimum IFM dose of 1000 J m(-2) demonstrated at least a 3 log reduction (LR) in viable MS2. Model-specific exposure times to achieve this IFM dose ranged from 2 to 266 min.

Conclusions: UV-C transmits into and through FFR materials. LR of MS2 was a function of model-specific IFM UV-C doses.

Significance and impact of the study: Filtering facepiece respirators are in high demand during infectious disease outbreaks, potentially leading to supply shortages. Reuse of disposable FFRs after decontamination has been discussed as a possible remediation strategy, but to date lacks supporting scientific evidence. The methods described here can be used to assess the likelihood that UV-C decontamination will be successful for specific FFR models.

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Figures

Figure 1
Figure 1
FFR interfaces and layers, (a) environment interface, (b) user interface, (c) outer layer, (d) internal layer, and (e) inner layer.
Figure 2
Figure 2
Dose–response relationship of MS2 inactivation on FFR coupons exposed to UV‐C. The data points represent the average LR of MS2 on FFR coupons exposed to UV‐C doses determined for the internal filtering medium using αIFM. The error bars represent ±1 standard deviation range for quadruplicate coupons (n = 4). The trend line is the biphasic mdel generated using the GInaFit freeware tool.
See this image and copyright information in PMC

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