If you work in a healthcare setting, or where there is dust, heat, humidity, or mist around you, respirators are necessary.  Respiratory protection is regulated by OSHA, which determines which type of respiratory protection is appropriate for each kind of hazard.  NIOSH regulates the manufacture and testing of face masks/respirators, and OSHA is responsible for their use.

Masks used by healthcare workers may be surgical, procedure, isolation, dental, or laser masks.  These masks trap germs and resist fluids.  Surgical masks protect the employee from microorganisms, body fluids, and large particles in the air.  They cover the mouth and nose loosely and are not sized for individual fit. Good hand hygiene must be practiced, such as washing hands before putting the mask on and taking it off.

N95 filtering respirators, “air purifying respirators” cover the nose and mouth.  A respirator classified as N95 means that 95% of most penetrating particulates will be filtered out. This type of respirator protects the wearer against breathing in small particles that contain viruses, such as in a healthcare setting.  For other occupational exposures, the respirators filter out dust, mist, heat and vapors that can be harmful to your health.  To be fully effective, N95 respirators must fit closely to form a light seal over the mouth and nose.  Persons with mustaches or beards may not be able to get a secure fit.  Respirators require fit-testing, to be sure there are no leaks.  There are fit-testing kits that are used to ensure their compliance to safety requirements.

Due to the fact that respirators are made of more dense material than facemasks, persons who have heart disease, lung disease, or other respiratory illnesses should consult a healthcare provider before using a respirator.

In cases of widespread illness, such as pandemic influenza, it is wise for persons who act as family caregivers or have to be in public transportation, etc., to stock up on these protective masks.

Source:
CDC