Published case studies on UV in-duct air and surface disinfection systems have demonstrated major reductions in indoor airborne concentrations of pathogens and allergens.
Robertson et al (1939) tested an installed in-duct air disinfection system and showed that up to 99% of the bacteria passing through air ducts could be removed with UV.
Allegra et al (1997) used a unitary UV system without a filter to reduce airborne concentrations of bacteria in a room, and obtained a 93-99% reduction of airborne counts within a matter of minutes.
In 1937, the application of UVGI to a school ventilation system dramatically reduced the incidence of measles (Wells 1955).
Rosenstern (1948) showed that UV in air conditioning systems could reduce cross-infections by 71% or more in a nursery.
Riley and O’Grady (1961) demonstrated the complete elimination of TB bacilli from hospital ward exhaust air using in-duct UV.
Schneider et al (1969) applied UV both in-duct and in corridors and effectively controlled pathogens in a hospital isolation unit.
Menzies et al (2003) studied the effectiveness of UVGI in a forced air ventilation system and found that respiratory symptoms in commercial office buildings were reduced from 3.9% to 2.9% after the installation of an in-duct UVGI system, representing a net decrease of 27% in respiratory symptoms.
A study on mold-sensitized children afflicted with asthma who lived in residential homes equipped with in-duct UV systems showed that UV air disinfection was effective in decreasing respiratory symptoms (Bernstein et al 2006).
A study by Dionne et al (1993) demonstrated a reduction in airborne concentrations of microorganisms in a day care center. Airborne concentrations of bacteria were reduced from about 500 cfu/m3 to about 160 cfu/m3 after 3 weeks.