Something’s are not meant to be used everywhere, that’s the case with the N95 masks, specifically a certain type.
In general, N95 mask has the capacity to filter up-to 95% of the airborne particles, in the present scenario & the limited availability of the Personal protective equipment, these masks should only be used by the health workers.
Now specifically researchers are now warning people not to use a particular type of N95 Mask that comes with valve, the valve is designed to make breathing out easier and is designed to be used by construction workers, in the current pandemic it can do more harm as this valve allows droplet release from the mask, putting others at risk, hence all Health Authorities are recommending against the use of Masks with valves.
Thanks for the update