[buybackoff]

It escapes during exhale since it naturally pushes the mask away and the fit becomes looser. During inhale air pushes the mask toward the face and the fit becomes tighter.

Most problems are during some, even light such as walking, physical activity when more air is needed. Inhaling is limited by the mask, but it cannot hold a strong exhale. I imagine sitting in a subway or a train should be fine. Hope to get on a train trip in 2 weeks so I would rather postpone my second covid, that's why I'm going for those inconveniences.