Einstein proved in 1905 that a photon of light can activate metal oxide (photocatalytic oxidation or PCO). Studies in the US have shown the process can create toxic side-effects, yet a company in the Czech Republic says they have created a powerful air-cleansing paint for indoor use
In a small, rather dilapidated factory on the outskirts of Prague, a company called Advanced Materials is putting titanium dioxide to use in something called photocatalytic paint, an incredibly clever, virtually translucent paint that actually cleans the air in your living room of everything from bacteria to cigarette smoke.
“Even in a concentration of one cigarette per cubic metre, you see very high degradation rate,” said Jan Prochazka, Advanced Materials’ co-owner. In one hour, he said, a cubic meter box used to test the paint is clean of cigarette smoke.
“We say [the paint will oxidize] ninety percent of all contaminants in 24 hours, but it’s much faster. It’s just to stay on the safe side,” Prochazka added.
There are two risks to this kind of solution. First, the paint has to sit on a base that can resist it and second, the byproduct of the paint has to be non-toxic.
Air-Cleansing cement for outside use has been available for nearly ten years and paint was introduced five years ago.
In 2002, after 7000 square metres of road surface in Milan, Italy, were covered with a catalytic cement, residents reported that it was noticeably easier to breathe – with the concentration of nitrogen oxides at street level cut by up to 60 per cent. […] The paint could cover a much greater surface area than cement, since every building and piece of street furniture could be painted with it. Photocatalytic cements and paving slabs are already used in Japan, where the market for such building materials is growing.
These outdoor solutions have proven the first risk has been controlled. The second risk, however, is not settled. Science labs in the US report increases in formaldehyde and acetaldehyde. They propose air-ducts or standalone units be setup with PCO, instead of used as an indoor paint, so the flow of air is controlled and then filtered with “chemisorbent oxidizer—sodium permanganate—downstream of the PCO device”.
Small, stand-alone active PCO units are available commercially, but Destaillats warns buyers that the performance of current products is uncertain. It is possible that some units produce harmful aldehydes and that catalysts become deactivated.
Berkeley Lab’s current research addresses only the large systems that can be incorporated into a building’s HVAC system. These systems are still in the experimental phase. Ideally, in-duct air cleaners should include several stages (such as the use of a chemisorbent after the PCO), but the cost of a multi-stage system may be cost-prohibitive for some.