There are several elastomeric respirators that are ventless or that have add-on vent filters. I’ve heard that some of these respirators are not that comfortable to wear for long periods of time due to increased humidity, rather than pressure drop or C02 accumulation. I’ve tried a 3M 6000 series respirator with the 3M 604 exhalation valve filter, and I’ve noticed no significant increase in breathing difficulty, but I didn’t use it long enough to determine if humidity accumulation is a problem.
Ventless disposables can also have humidity issues, so you’re probably better off with an elastomeric anyway.
There are several elastomeric respirators that are ventless or that have add-on vent filters. I’ve heard that some of these respirators are not that comfortable to wear for long periods of time due to increased humidity, rather than pressure drop or C02 accumulation. I’ve tried a 3M 6000 series respirator with the 3M 604 exhalation valve filter, and I’ve noticed no significant increase in breathing difficulty, but I didn’t use it long enough to determine if humidity accumulation is a problem.
Ventless disposables can also have humidity issues, so you’re probably better off with an elastomeric anyway.