Indoor air quality, dust mite allergens and asthma

This controlled trial evaluated allergen and water vapour control measures on the level of house dust mite (HDM) Der pI allergen and indoor absolute humidity, concurrently with changes in lung function measured by am/pm peak flow and questionnaire indices of clinical well being in 54 subjects who completed the protocol. Allergen control involved protein denaturing by steam cleaning and exposure was minimised by mattress encapsulation using microweave envelopes. Mechanical heat recovery ventilation units (MHRV) increased air change rates and lowered internal water vapour pressures during the winter months. Mean Der pI reservoirs in carpets and beds were reduced by over 94% and 86%, while the MHRV units reduced water vapour pressures in the active group by an average of 12%. Lung function measurement and health questionnaire data confirmed a significant clinical improvement in the active group compared with the control