House dust mites - the minute creatures which spark asthma attacks - are found in very high levels in two thirds of homes, according to a survey by the Building Research Establishment. The findings explode the myth that mites, invisible to the naked eye, mostly inhabit mattresses. In some properties more were found in bedroom and living-room carpets. Fewer than one in three homes was below recommended mite levels and one count showed 15,840 mites - 3000 higher than the previous highest recorded. All houses, and 99% of dust sample yields peaked in autumn. House dust mites contribute to 1500 asthma-related deaths each year.