"The air inside an office is probably 10 times more polluted than that outdoors," says Gary Raw, director of the Centre for Safety Health and the Environment at BRE. According to Raw, a typical office will contain a couple of hundred pollutants seeping from furnishings, glues and paint, and these are added to by other nasties from photocopiers, cleaning products and even air fresheners. This chemical cocktail can be more than unpleasant. "In some cases, people's health is affected," Raw explains.
And if health is affected, then sickness absence increases and productivity at work decreases.
Dr Hazim Awbi, at the University of Reading's department of construction management and engineering, says: "Professor Fanger from Denmark, who is a world leader in indoor air quality issues, has shown that productivity can increase by up to 6 to 7% where air quality increases."
Convinced that developers would pay a premium for a device that improves office air quality, air-conditioning manufacturer Carrier has developed an air purification unit for offices that contains a catalytic converter designed to neutralise many of these harmful chemicals. The unit is claimed to improve the air quality of offices by degrading noxious and evil-smelling molecules to inoffensive compounds such as carbon dioxide and water.
The unit has yet to be officially launched, but the company has already sold 3000 of the modules to French development company SARI, for an office block being built in the La Defense district of Paris. Carrier is being cagey about the name of the tenant: all the company will disclose is that it is a Canadian-based firm. "We've met the developer and he told us that indoor air quality was among the most important items for this building," explains Olivier Josserand, product development engineer at Carrier France. Josserand says that by improving the building's air quality, the developer was looking for ways to add value to the building to make it attractive to very prestigious customers.
The unit has been 10 years in development. The company's research and development centre in America started work developing air purification systems for the aviation industry. "The idea was to develop an air purifier for aircraft cabins, after the plane manufacturers asked us to find a suitable system," recalls Josserand. But with the topic of indoor air quality rising on the developer's agenda, it was not long before the company's commercial equipment arm was asking for a similar system to be developed for buildings.
The purification module has been designed to slot into the company's existing room air-conditioning units for offices. These units are known in the trade as fan coil units because – unsurprisingly – they contain a fan and a heating and cooling coil. They are designed to circulate the air in a space by drawing it through the unit, heating or cooling it as necessary, and then returning it to the room. With the air purification module installed, these fan coil units will now clean the air as well as adjusting its temperature before returning it to the room.
The module consists of three primary components: a filter, an ultraviolet lamp and a titanium dioxide catalyst. The unit's high efficiency filter is the first line of attack against air pollutants. The air passages through this element are so small that dust and dander become trapped in the filter and are removed from the air.
Next the air passes beneath the ultraviolet lamp. "Ultraviolet kills living organisms," explains BRE's Raw. This part of the unit kills bacteria such as the tuberculosis bacillus and viruses such as influenza present in the air. It is also claimed to "de-activate" pollen and mould spores and to neutralise odours. But aside from its role as virus annihilator, the UV lamp also serves to activate the titanium dioxide-coated catalyst.
The catalyst is the last of the unit's array of weapons aimed at destroying impurities in the air. In the same way the catalyst in a car converts many of the harmful products in the exhaust into harmless compounds, so the catalyst in the purification unit converts harmful toxins in the air into harmless compounds.
To explain how the catalyst works, it is necessary to understand some rudimentary chemistry. Titanium dioxide is a semi-conductor. Activated by the energy from the ultraviolet lamp, the catalyst's titanium dioxide coating transforms the water and oxygen molecules in the air into aggressive molecules called free radicals. These are highly reactive molecules. "They eat stuff up," explains Jim Freihaut, Carrier's indoor air-quality programme leader.
The free radicals then combine with the benzene and formaldehyde and other volatile organic compounds in the air, oxidizing them into benign products such as carbon dioxide and water. Freihaut describes the free radicals as a bit like the computer game Pacman: "They just devour these compounds and destroy them," he says.
In fact, the combination of the ultraviolet lamp and the catalyst is so effective it will even exterminate the anthrax bacteria. "The UV decimates anthrax," says Freihaut. The bacteria can even be destroyed in its spore form, which is much harder to annihilate – although a much more powerful version of the lamp is needed.
The system is not perfect, however. Josserand is quick to point out that this system will not completely remove pollutants from a room in one cycle. "You'd have to pass it through several times to get close to zero pollutants," adds Freihaut.
Still, there are many advantages to the catalyst technology. "In contrast to carbon filters, this technology is auto-regenerative; pollutants are destroyed and there is no need to change the catalyst," Josserand explains. Maintenance of the purification unit is simply a question of replacing the filter when it becomes clogged, or replacing the lamp when it fails.
But in addition to improving the air quality inside a building, the active air cleaner is also being promoted as a way to reduce a building's energy use. Carrier has put together a control unit for their air-conditioning fan coil, designed to regulate the amount of fresh air supplied to a space. Called "demand control ventilation", the system works by using the fan coil unit to continuously circulate the room's air through the air purifier – keeping it free of impurities. The control unit then adjusts the amount of fresh air supplied to the room based on the amount of carbon dioxide present in the space.
This saves energy because the fresh air must be filtered and either heated or cooled before being supplied to the room. Josserand says the system will suitable for areas that have a variable occupancy such as meeting rooms or classrooms.
For now though, the development team is hoping the air purification unit's performance on the first commercial installation is a success. "We're working with the Institute Pasteur in France and with Harvard University in the USA to get independent verification of the results," says Josserand.
In the future, it may well be worth taking that last gulp of clean, purified air before leaving the office and hopping into the car for the journey home. But be sure it is a large gulp – the Commonwealth Scientific and Industrial Research Organisation of Australia has just issued a warning that air toxins inside a new car can be over four times higher than recommended levels.