Does Masks With An Exhalation Valve Prevent Viruses

The function of the exhalation valve is to reduce the exhalation resistance of the protective mask. The reason why medical protective masks do not allow an exhalation valve is that an open exhalation valve may discharge droplets or bacteria from the mask wearer, which may threaten patients who are undergoing surgery.
Therefore, if wearing a protective mask is to prevent yourself from the virus, it is no problem to choose a more comfortable protective mask with an exhalation valve; but if a person suspects that he is infected or has been infected by some virus, he should take initiative to wear a mask without an exhalation valve to protect others.