Issues Affecting Respirator Selection for Workers Exposed to Infectious Aerosols: Emphasis on Healthcare Settings

The goal of occupational health practice is to protect the health of workers by preventing diseases and injuries from occurring. When work activities are anticipated, recognized, or found during an investigation to involve risks to workers' health, preventive measures should be taken to control hazardous exposures in the workplace. Respirators are often used to control inhalational exposures to hazardous airborne contaminants, including infectious agents. Of the three methods available for selecting a respirator, the expert opinion method is used most frequently to recommend respirators for controlling exposures to infectious agents. The size of the particles comprising an infectious aerosol has received particular attention relating to the selection of respiratory protection for healthcare workers. Conflicting meanings of the term “droplet” are central to this issue and may be partly responsible for confusion concerning the particle sizes that surgical masks are unlikely to protect against. Although workers caring for patients with contagious respiratory infections are at risk of exposure to large-particle droplets greater than 100 micrometers in diameter, their risks of inhalational exposure to infectious particles are likely to be predominantly to an aerosol consisting of a mixture of evaporating droplets and droplet nuclei that remain suspended in room air for prolonged periods. Because surgical masks are intended to be used only as barriers against large-particle droplets, only respirators certified by the National Institute for Occupational Safety and Health should be used as part of a strategy for protecting workers against inhalational exposures to infectious aerosols. The issues outlined in this paper are focused on workers in healthcare settings, but also apply in other settings where workers may be exposed to infectious aerosols.