The bactericidal effects of negative ions in air

The use of negative ions to improve indoor air quality has attracted increasing attention in recent years. Although the physical action of air ionisers is accepted, there is still debate over their apparent biocidal action. A recent clinical trial in an intensive care unit suggested that air ionisers may have a role in reducing the transmission of infection in healthcare environments1 and several authors have reported that ions inhibit the growth of a range of microorganisms. A further understanding of this process was gained through bench scale experiments exposing sessile cultures to positive and negative ions2. The aim of the work presented here was to follow on from the bench scale experiments to investigate the efficacy of negative ions with aerosolised microorganisms.