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. 2016 Jul;13(7):569-76.
doi: 10.1080/15459624.2015.1043050.

Respiratory source control using a surgical mask: An in vitro study

Rajeev B Patel  1 , Shaji D Skaria  1 , Mohamed M Mansour  1 , Gerald C Smaldone  1
Affiliations

Respiratory source control using a surgical mask: An in vitro study

Rajeev B Patel et al. J Occup Environ Hyg. 2016 Jul.

Erratum in

  • Correction.
    [No authors listed] [No authors listed] J Occup Environ Hyg. 2022 Jun;19(6):409. doi: 10.1080/15459624.2022.2065169. Epub 2022 Apr 20. J Occup Environ Hyg. 2022. PMID: 35442863 Free PMC article. No abstract available.

Abstract

Cough etiquette and respiratory hygiene are forms of source control encouraged to prevent the spread of respiratory infection. The use of surgical masks as a means of source control has not been quantified in terms of reducing exposure to others. We designed an in vitro model using various facepieces to assess their contribution to exposure reduction when worn at the infectious source (Source) relative to facepieces worn for primary (Receiver) protection, and the factors that contribute to each. In a chamber with various airflows, radiolabeled aerosols were exhaled via a ventilated soft-face manikin head using tidal breathing and cough (Source). Another manikin, containing a filter, quantified recipient exposure (Receiver). The natural fit surgical mask, fitted (SecureFit) surgical mask and an N95-class filtering facepiece respirator (commonly known as an "N95 respirator") with and without a Vaseline-seal were tested. With cough, source control (mask or respirator on Source) was statistically superior to mask or unsealed respirator protection on the Receiver (Receiver protection) in all environments. To equal source control during coughing, the N95 respirator must be Vaseline-sealed. During tidal breathing, source control was comparable or superior to mask or respirator protection on the Receiver. Source control via surgical masks may be an important adjunct defense against the spread of respiratory infections. The fit of the mask or respirator, in combination with the airflow patterns in a given setting, are significant contributors to source control efficacy. Future clinical trials should include a surgical mask source control arm to assess the contribution of source control in overall protection against airborne infection.

Keywords: Aerosol; environmental controls; respirator; surgical mask.

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Figures

Figure 1.
Figure 1.
Model of source manikin, receiver manikin, and environment interplay. Model of source manikin, receiver manikin, and environment interplay. Parameters can be set or measured. Dilution is an effect of the environment on the concentration of produced aerosols. Filtration (capture efficiency) is a function of the mask used and takes place at both the source and receiver. Particles that are not captured can be deflected (outward leakage around the faceseal perimeter) by the mask at the source and carried away from the receiver by the environmental flow. Breathing patterns simulate adults with tidal breathing or coughing.
Figure 2.
Figure 2.
No flow chamber with, 0 air exchanges per hour (ACH). Schematic representation illustrating a chamber, containing the ventilated manikin heads 3 ft apart. Source head was connected to a nebulizer and exhaled radioactive aerosols. A filter was attached to the Receiver head to capture and quantify inhaled radioactive aerosols (exposure) (A). Hospital room chamber, with 6 ACH. Schematic representation illustrating a chamber, containing the ventilated manikin heads 3 ft apart. Source head was connected to a nebulizer and exhaled radioactive aerosols. A filter was attached to the Receiver head to capture and quantify inhaled radioactive aerosols (exposure) (B). Negative pressure room chamber, with 12 ACH. Schematic representation illustrating a chamber, containing the ventilated manikin heads 3 ft apart. Source head was connected to a nebulizer and exhaled radioactive aerosols. A filter was attached to the Receiver head to capture and quantify inhaled radioactive aerosols (exposure) (C).
Figure 3.
Figure 3.
Schematic representation illustrating cascade impaction experiments.
Figure 4.
Figure 4.
Exposure data for tidal breathing, expressed as a percent of aerosol exhaled with a two-sided 95% CI, plotted for different masks on the Source or Receiver. An asterisk (*) denotes significance for a p-value <0.05 using the Kruskal-Wallis one-way analysis of variance. S = Source, R = Receiver, MaxEx = Maximum Exposure, SMnat = natural fit surgical mask, SF = SecureFit Ultra fitted surgical mask, N95 = 3M N95 respirator, N95vas = 3M N95 respirator with a Vaseline seal.
Figure 5.
Figure 5.
Exposure data for cough, expressed as a percent of aerosol exhaled with a two-sided 95% CI, plotted for different masks on the Source or Receiver. An asterisk (*) denotes significance for a p-value <0.05 using the Kruskal-Wallis one-way analysis of variance. S = Source, R = Receiver, MaxEx = Maximum Exposure, SMnat = natural fit surgical mask, SF = SecureFit Ultra fitted surgical mask, N95 = 3M N95 respirator, N95vas = 3M N95 respirator with a Vaseline seal.
Figure 6.
Figure 6.
Mask capture efficiency (percent of aerosol exhaled with a two-sided 95% CI) mask on Source. (Upper Panel) Tidal Breathing. (Lower Panel) Cough.
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