The development of wool-based passive filters to improve indoor air quality

It is well known that wool carpets and upholstery permanently remove many gaseous pollutants from the air, thus improving indoor air quality, and peoples’ wellbeing. The aim of the work reported here was to develop wool-based filters that could be used in homes and offices to improve indoor air quality. The abilities of wool, jute, and some other materials used in building interiors, to absorb common indoor air pollutants, formaldehyde, sulphur dioxide and nitrogen oxides were compared. Testing was conducted in a chamber that reproduced the conditions found in a typical room. Wool and jute were found to give high levels of absorption and the results were used to design six types of wool-based filters that were intended to be compact, with high rates and capacities of absorption. The filters were passive, relying on high surface areas and diffusion, rather than forced air circulation, thus minimising their net environmental impact. Filters based on wool yarn, roving, balls and unbacked carpet, were all very effective, absorbing between 94 and 96% of the air pollutants over six hours. This study has shown that wool-based passive filters can significantly improve indoor air quality, and represent a new use for wool.