Unless you’ve been properly fitted for the mask, you’re rolling the dice. It’s entirely possible you’re getting ZERO benefit.
A few years back, I was doing EMS and had to fly a patient 2.5 hrs with an N95. I felt dang-near hypoxic from the restriction and ATC had a really hard time understanding my transmissions. And it was nasty. There was so much condensation inside the mask when we arrived...it was necessary, but not fun.