Sick building syndrome is a term used to describe a range of symptoms suffered by office workers, such as headaches, fatigue, difficulties in concentrating and respiratory problems.

It has been estimated that these symptoms occur in 20% to 30% of office workers.

Some researchers believe that high levels of bacteria and fungi in ventilation systems could be to blame.

These micro-organisms have been detected in high concentrations on cooling coils, filters, drip pans, humidification systems and in the ductwork of the supply air.

A report in the journal Occupational Environmental Medicine says that the health of office workers improved after high intensity ultraviolet lights were installed in the ventilation systems serving three floors of an office building in Montreal, Canada.

In total, 113 management employees worked on these floors, of which over 80% were non-smokers.

Switched on and off

The lights were switched on and off for a total of four alternating blocks of three weeks each.

The levels of airborne bacterial and fungal organisms remained the same throughout the study, but were virtually eliminated from the surfaces of the ventilation system within three weeks.

The employees reported fewer symptoms when the ultraviolet lights were operating and took less sick leave. They were aware that the lights had been installed, but could not tell when they had been switched on or off.

Employees are not directly exposed to the UV rays, so the system is safe, and is relatively cheap, say the authors.

They suggest these lights could be installed in the air conditioning, ventilation, and central heating systems of most existing modern office buildings and high rise towers, and would kill a wide range of microbes.

This might alleviate symptoms often referred to as sick building syndrome, they conclude.

The ability of ultraviolet lighting systems to kill microbes has been known for many decades. It is used in hospitals, food processing plants and pharmaceutical manufacturring.

Until now it has not been used in ventilation systems because of technical limitations.