Risks to health of carbon monoxide and other combustion gases in energy efficient homes

Revisions of the UK Building Regulations are resulting in changes in the design, construction, heating and ventilation of new and refurbished homes. There are concerns that inadequate ventilation of these energy efficient homes could result in increased levels of indoor pollutants. This study considers the possible risk to occupant health due to exposure to combustion by-products, such as carbon monoxide (CO). Measurements of combustion pollutants during the 2010/11 heating season were undertaken in 14 homes built/refurbished in accordance with 2006 Building Regulations or to a higher standard of energy efficiency, as well as 5 older homes over a two week period. No WHO indoor air guidelines for CO were exceeded in any home. It was found that there was a significant difference between CO and nitrogen dioxide in the kitchen and the bedroom of the main study homes. Modelling of CO demonstrated how situations of low ventilation combined with high and also moderate source emission rates could potentially lead to air quality guidelines being exceeded. Combustion, heating elements and some aerosols were found to greatly increase the number of ultrafine particles (UFPs). Currently, no guidelines for UFPs in air are available and there is limited literature reporting their measurement. The air quality measurements do not show that energy efficient homes pose greater risks to health of occupants from combustion pollutants than other homes. However, modelling suggests some scenarios could produce exposure to CO exceeding health based guidelines. The study is considered as a preliminary investigation, not representative of the wide range of different house types and occupant behaviours that may influence pollutant levels and exposure of occupants. It does provide valuable indicative data and identifies a need for further work as current knowledge about indoor air quality in energy efficient homes is limited and possible risks to health have not been fully evaluated.