CDC now says valved N95 has better source control than cloth/surgical masks [pdf]
I think this post&#x27;s title is heavily editorialized, and is not reflected in the study&#x27;s conclusion, which is quite confusing:<p><pre><code>    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
</code></pre>
Note &quot;nearly as well&quot;. This will be contradicted by the conclusion. Also it&#x27;s quite logical that if you tape over the exhaust valve, it will behave like a non-valved mask? When compared to models without valves:<p><pre><code>    the maximum particle penetration through the unmitigated 
    FFRs evaluated in this study was 55%, which occurred at 
    55 lpm, while the maximum penetration for surgical masks 
    was 17% for the filter media and 76% when considering fit
</code></pre>
17% seems quite a bit better than 55%. And then they conclude with<p><pre><code>    FFRs with exhalation valves can reduce 0.35-μm MMAD
    particle emissions more consistently than surgical 
    masks, procedure masks...
</code></pre>
followed immediately by:<p><pre><code>    With mitigations that cover the exhalation valve, 0.35-
    μm MMAD particle emissions can be limited to 5% if the 
    filter media does not interfere with providing a good 
    seal to the exhalation valve
</code></pre>
5% is where the number in N95 comes from, that&#x27;s not any better?<p><pre><code>    the exhalation valves could be improved by establishing 
    criteria for valve performance
</code></pre>
Why would it matter to improve the valve design, if it&#x27;s being covered?<p>The conclusion is that taping with micropore performs just as well as a non-valved mask, but blocking the valve completely with an ECG pad performs <i>better</i> than not having a valve at all. How?<p>Are there other design differences in valved masks that account for the difference? If I attach an ECG pad to the center of a non-valved mask would it improve performance?