Surface-catalysed reactions on pollutant-removing building products for indoor use

In order to evaluate the potential for emission of secondary reaction products from building materials designed to remove pollutants from indoor air, four samples of ceiling tiles – three commercially available and one custom-made – were investigated in chamber experiments. The chambers were irradiated with artificial light simulating indoor conditions and formaldehyde as well as several VOCs (2-butanone, n-butanol, toluene, hexanal, n- butylacetate, 2-butoxyethanol, α-pinene, benzaldehyde, n-decane, limonene and 1,2-dichlorobenzene) were added. Depending on the individual substrate–substance combination, it was possible to identify secondary emissions, e.g. formaldehyde, furfural, acetophenone, n-butylbutyrate, n-butyl-i-butyrate, n-butylpropionate, 4-heptanone, acetic acid, i-butyraldehyde and crotonaldehyde. These were generated by cleavage, hydrolysis, rearrangement or radical reactions. Some of these reactions also occurred with samples not containing photocatalysts. All these secondary emissions have to be taken seriously into account when evaluating the performance of materials designed to remove pollutants from indoor air, as they can prove detrimental to human health.