Face masks are designed to be used for full on, consistent work around far more harmful materials and hazards. They can be kept permenantly and the filters can be swapped out to keep them fresh. There are a wide variety of face masks available, dependent on your application purposes and situation.
Without an effective seal to the face, the mask cannot filter the air you breathe. "Press to check" filters allow the wearer to easily check the fit of their mask, every time it is used, without the need for another device.
The table below highlights the various different levels of protection that each face mask offers. Most face masks have a rating of either P3, A2P3, ABEK1P3.