Are disposable n95 respirators with exhalation valves effective against germs? are they to be replaced after about 8 hours? and should they be tossed after taking them off, even if 8 hrs haven't elapsed? or can they be stored for later wearing. thx!

Very effective : N95 face masks are epidemiological protection masks, they have superior level of protection, you can use them for days if they are clean. However they are expensive and should be used only for specific reasons.

N95 respirators: are very effective for protecting against germs if there is a good fit and they are in proper working order. In the past, they would be tossed, now they are being stored and used over and over. Per CDC, discard N95 respirator that is obviously damaged or become hard to breath through, or if it is soiled / contaminated with blood, respiratory or nasal secretions or other bodily fluids or close cont