We go to hospital for treatment and improvement - few of us expect the experience to leave us worse off. Yet a tenth of all hospitalized patients in industrial nations pick up an infection in hospital that often prolongs their stay and leads to more treatment. In developing countries, that proportion rises to a quarter.

Hospital acquired infections (HAIs) are also costly to the health system. Recent estimates suggest HAIs cost $6.7 billion each year in the United States of America and $1.7 billion in the United Kingdom.

In hospitals many people, some of whom are very ill, mix together, and so do any bacteria and viruses they are carrying. Some of these pathogens pose a serious health threat, especially to people with compromised immune systems and often people in hospital do have lowered ability to fight off infections.

Bacteria and viruses such as the flu, TBC, pneumonia and MRSA, are known to be also transmitted via the air and there is increasing evidence that up to 20% of Hospital Acquired Infections (HAIs) are transmitted this way. Although clean hands campaigns such as the World Health Organization's Clean Care is Safe Care, can make an enormous contribution to reducing the level of HAIs and protecting patients, other means are needed to tackle airborne and surface-related threats.

Researchers have investigated a range of ways to disinfect air and surfaces including filtration, dilution and even essential oils. One tried and tested method is ultraviolet irradiation. The light in the short-wave UVC band provides a strong germicidal effect, which can be used to disinfect air, surfaces and water. UVC radiation works by damaging the pathogens' DNA, leaving them unable to replicate.