Surgical mask

Three surgeons operating with surgical masks. Fitzsimons Army Medical Center, circa. 1990

A surgical mask is designed to be worn by health professionals during surgery and at other times to catch the bacteria shed from the wearer's mouth and nose.

Outside health care facilities, simple, inexpensive surgical masks are commonly worn in heavily polluted various industrial centres in East Asia. More recently, they were widely used in China, Hong Kong, and Vietnam during outbreaks of the SARS virus.

Construction

Most "real" surgical masks used in operating rooms for the purposes of reducing infection are made of paper or non-woven, and are disposed of after each use.

Effectiveness

Simple surgical masks do reduce the spread of bacteria and aerosols. Apart from protecting the wearer from splashes in the mouth with body fluids they are designed to protect others from the wearer's oral bacteria. They are not designed for protecting the wearer from inhaled particles.

Viral particles are far too small to be caught in the fibres of a regular surgical mask. Thus, a mask wearer would not be less likely to catch a viral disease than someone not wearing a mask. However, an already infected person wearing a mask may slightly reduce his chances of infecting others, as it may catch droplets of fluid expelled during sneeze or cough.

The NIOSH N95 standard mask is designed to protect the wearer from viral particles. Another benefit of masks, even ones permeable to viruses, is to remind the wearer not to touch his face. Direct skin contact after touching a surfaces with viruses on it (termed a fomite) may transfer viruses which are not typically airborne.

A surgical mask will trap some dust but is a lot less effective than masks designed for this purpose.