Retro-fit Infection Control

Ultraviolet light in the c-band range (225–302 nm) is lethal to micro-organisms and is referred to as ultraviolet germicidal irradiation (UVGI). It is well known for its germicidal – or germ killing – properties and is used extensively for water and surface treatment. Historically, airstream disinfection has proven less predictable. This is due to underspecifying the UV-C dosage and poor design. UVGI works by cross linking the nucleic acids (DNA & RNA) which prevents replication and proliferation of micro-organisms such as viruses, bacteria, spores, moulds, yeast and fungi. It is important to use the correct UVC dosage in order to achieve high kill rates.

Low intensity UVC can be used for surface treatment as there is a long UVC exposure time whereas high intensity UV-C is required for air treatment as the exposure time is short.

The UV dosage to achieve microbial kill varies considerably between micro-organisms, with spore-forming microbes being more resilient to UV attack than vegetative cells, for example. Microbial spores are akin to plant seeds and are adapted to withstand extreme environments whereas so-called vegetative cells are those which grow and divide – a plant seed can survive in, and actually requires, dry conditions whereas the vegetative new shoot after germination requires water.