Quote Originally Posted by oj88 View Post
The one-way valve lets you expel the air more easily (less resistance) and also so that you'll be breathing in less of your own breath. It doesn't help with inhaling (valve closed).

As a side note, this type shouldn't be used to mitigate Covid-19. The one-way valve isn't filtered so an infected person's breath would just vent out, unfiltered.
Yup I only used it outdoors when I jog around the village wala naman ako usually kasabay


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