The danger of exposure to tuberculosis (TB) exists primarily in facilities in which people with TB are likely to mingle with uninfected susceptible people. Such places include, among others, healthcare facilities in areas where TB is prevalent, shelters for the homeless in large cities, drug treatment centers, and prisons. If a given facility is identified as hazardous, an effective method for interrupting airborne transmission of TB is air disinfection with ultraviolet germicidal irradiation (UVGI). In this article, implementation of this method will be discussed: where, within a given building, UVGI fixtures should be installed; and what fixture design should be chosen for each location.
Where to install ultraviolet (UV) fixtures depends on where the hazard of airborne TB exists, and that depends on the behavior of infected people and the behavior of infectious airborne particles. Patients with known active TB normally are sequestered in isolation rooms where special precautions are taken to avoid transmission of infection. However, as stated succinctly in 1967 in a document accepted by the National Tuberculosis Association Board of Directors: “It should be made clear that the greatest risk of infection arises from the individual with undiagnosed or unsuspected tuberculosis.” Such people usually are unaware that they are infectious. They may be seated in clinic waiting rooms, walking the hospital corridors, or visiting in patients' rooms. If the unsuspected case is a member of the housekeeping or healthcare staff, he or she may be found anywhere in the building. The behavior of infectious airborne particles is equally unpredictable.