Technical Report.  Filtering Facepiece Respirators with an Exhalation Valve: Measurements of Filtration Efficiency to Evaluate Their Potential for Source Control.  DHHS (NIOSH) Publication No. 2021-107

The study problem is clearly defined in three computer generated exhalation emission photographs:

1) A properly fitted filtering facepiece respirator (FFR) without an exhalation valve showed less than 5% of the particles escape on exhalation.  

2) The FFR with an exhalation valve allows 20% of the particles through the valve.

3) a barrier face covering without a good fit (seal to the face) releases 50% of the particles.

All types of FFRs and masks were tested at "moderate exercise" levels of 85 liters per minute (lpm) as specified in NIOSH certification tests.  Two lower breathing rates were also compared.  But the effects of a cough and sneeze were not investigated which limits this study.

Another study limit was the test method in which the FFRs and masks were sealed with beeswax to the inward and outward testing apparatus.  This eliminated the fit of the respirators as a factor.  

The mitigation (blocking) of the FFR valves was done with 1) surgical tape placed over the valve inside the FFR, 2) electrocardiogram (ECG) pads pressed onto the interior opening of the valve, and 3) placing a surgical mask over the exterior of the FFR.  

NIOSH also tested unregulated face coverings of four models of surgical masks, seven procedure masks, six cloth face coverings, and two fabric masks from cotton t-shirts.  The cloth face coverings, two had filter inserts and three had exhalation valves. I will not report this data because it seems obvious that starting with a poorly-fitting, inferior-filtering cloth mask and adding a valve to make it worse is not worth reviewing.

Conclusions

But in the body of the study it noted a reason some were as low as 1% is that some of the valves did not open during the test.

It seems to me that data from these irregularly operating valves only confounds conclusions and should have been separated from general conclusions since one could not, in practice, assume that the valve would be closed during use.  And the valve would be especially likely to open on a cough or sneeze. 

The remaining important conclusion are as follows;

This is important since if mitigation with an ECG pad is practiced, it is necessary for hospitals to be well-aware of this model and other similar models in order to avoid purchasing it.

The final conclusions are:

With mitigation measures such as surgical tape or an ECG pad secured inside, the FFRs can perform nearly as well as an FFR with no exhalation valve. 

And

During shortages of respiratory protection, FFRs with an exhalation valve provide an additional source of equipment for workers who need respiratory protection and are concerned about source control. 

The problem with this is all EEG pads are not the same.  Having had recent experience on a monitor for several days and becoming visibly allergic to one brand, I was plastered with three different brands of EEG pads, each with different degrees of adhesion. One also has to wonder when a mask gets damp inside, would the pad still adhere? 

These uncertainties aside, the good news is there are large supplies of these valved respirators that could be used in an emergency with this mitigation.  And it looks like the study was released just in time for this current one.

-----Original Message-----
From: John Callen <jbcallen**At_Symbol_Here**GMAIL.COM>
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Sent: Fri, Dec 11, 2020 11:47 pm
Subject: [DCHAS-L] NIOSH Technical Report P/N 2021-107: Filtering Facepiece Respirators with an Exhalation Valve: Measurements of Filtration Efficiency to Evaluate Their Potential for Source Control