If I plan to wear something in the baking, humid heat for more than 5 minutes, that's where the respirator comes in handy.
Really not sure where this "3" number comes from though. Not enough thinking around all this mask malarkey. If the masks is there to protect others, then who cares how often it gets changed. The cloth/surgical masks are certainly not there to protect the wearer (I'd like to hear someone justify how it would protect the wearer, considering all the air intake comes from the air gaps).