Thread by @ghhughes

Are valved masks cooler? I tested 3 different 3M N95s to try to learn more about the effect of valves on heat in respirators.

Not much mathematical difference on average, under these specific conditions, with these 3 masks:

V-Flex +7.3°C
Valved Aura +7.3°C
No Valve Aura +7.5°C

I expect that results could vary dramatically under different conditions, including temperature, humidity, airflow rate, mask model and more. Even so, I was surprised that the valve didn't make a more substantial difference in average in-mask temperature.

I also tested valved and unvalved Auras during 15 minute outdoor walks in mixed shade and sun and got a similar lack of difference in average in mask temperatures (using different testing gear with 10 second intervals between samples).

The ambient readings were subject to heat from direct sunlight in the mixed shade and sun walk, so it's a bit hard to evaluate the difference in temperatures. I'm not even going to try to average them for deltas.

First mask is a valveless 3M Aura 9210+, 2nd is a valved 9211+.

The walking test was in ambient relative humidity of between ~35 and 40%.

I think a lot more tests are needed as these preliminary results are a bit limited and inconclusive. But they do suggest not to count on much temp reduction just from the addition of an exhalation valve.

(One issue that may be confounding my results is that all the masks I tested are very breathable masks - some of the best N95s available - which may make the airflow enabled by the exhalation valve more redundant than in the case of valves on less breathable masks.)

(I also don't know if that increase in temperature above ambient in between tests is due to the 1 cm proximity of the thermocouple next to my face, or if it's thermal conduction in the wire that is taped to my cheek to allow ot to fit under the mask up to sensor at the end.)