The control was with negative pressure(demand) masks;
I haven’t seen a demand pressure scba on any ships I’ve been on, they’ve all been positive pressure… I will reiterate my experience not having any issues in fire school with a two inch beard- the edges were well groomed though, it wasn’t scraggly.
Positive pressure scbas also have the advantage in that the tank duration tends to be the same. Demand set ups have an issue with folks sucking air too fast.
A bigger issue is out of shape folks who’ll pass out or potentially have a cardiac event or just not be able to fully engage in event of fire/emergency. Is MSC going to institute a PT test annually, with cardio events, be it a run/bike/swim?
I understand on tankers being clean shaven as respirators meant for hazmat/fumes don’t seal with facial hair, if they say it’s for cbrne that’s another thing, but a beard with the right fire fighting setup prolly wouldn’t be an issue.