IAQ | RESEARCH n If a pollutant is claimed to be removed, what process would be applied? In the case of absorption (or other fixation process), is it proven over time, taking account of possible re-release? In the case of decomposition, what are the by-products and their effects? n Are the claims based on independent research? n Is data available from existing case studies? Some of these knowledge gaps may be filled in the future; the complexity of others means a precautionary approach will be required The following examples illustrate the importance of these questions. Photocatalytic removal using titanium dioxide this has been studied for many years to address a range of pollutants, with potential indoor and outdoor applications, including paints or wall coverings and internal duct surfaces. A recent independent comprehensive review6 on its potential to reduce levels of nitrogen oxides (NOx) concluded there is little evidence of an impact in outdoor applications, or that the impact would be very small and require very large exposed areas. It does appear to reduce NOx levels when applied indoors, but there remains much uncertainty as to other possible consequences for example, other hazardous pollutants such as ozone may be generated from the photocatalytic decomposition of NOx and other air pollutants. VOC-reducing materials a number of claims are being made about materials that may help reduce indoor VOC levels, either by absorbing or decomposing them. One example is wool, which has been shown to have VOC-absorbent properties. The extent would depend on the type of wool, and the air would need to be in contact with the wool, which implies applications for furniture, floor and wall coverings rather than insulation.7 The body of evidence is not yet substantial, and the effect may be small, but long-standing historic applications mean there is little risk of unintended consequence. Indoor planting is a large R&D topic in itself, so it is not discussed here but, in addition to recent CIBSE Journal articles, a CIBSE publication on this is planned. Other new products claim to decompose VOCs into inert products, which would then be either released into the air or bound to the product in question. However, there is little public data on the mechanisms and by-products, and claims should be examined carefully. An important conclusion from this evolving field is to follow the precautionary principle and apply source control, as some effects on health may only manifest themselves in the long term, as in the case of asbestos and lead paint. This does not prevent innovation, but requires a cautious review of claims, possible effects, and monitoring and evaluation, to keep new uses under review. CJ Articles in the next few months will cover other topics, including housing refurbishment and its impact on comfort, air quality, humidity and energy consumption; and air quality monitoring procedures and equipment. DR JULIE GODEFROY is technical manager at CIBSE References: 1 I ndoor air quality at home, draft guidance consultation, bit.ly/CJSept19NICE 2 Guidelines for indoor air quality: dampness and mould, World Health Organization, 2009. 3 Electromagnetic fields and public health Electromagnetic hypersensitivity, Backgrounder, December 2005. 4 SCENIHR, Opinion on potential health effects of exposure to electromagnetic fields (EMF), European Commission, 2015 5 Cullinan P, Building health and ill-health, presentation at annual BSRIA Briefing, November 2016, London. 6 Defra, Air Quality Expert Group, Paints and surfaces for the removal of nitrogen oxides, Prepared for: Department for Environment, Food and Rural Affairs; Scottish Government; Welsh Government; and Department of the Environment in Northern Ireland, Crown copyright 2016. Establishing the individual impact of multiple environmental factors on indoor air quality is highly problematic 7 Mansour E, Marriott R, Ormondroyd G, Sheep wool insulation for the absorption of volatile organic compounds, Young Researchers Forum III Innovation in Construction Materials, 12 April 2016. 72 September 2019 www.cibsejournal.com CIBSE Sep19 pp70-72 Research Air quality.indd 72 23/08/2019 15:24