One of the most ______ source of indoor air pollution is the allergens. House dust mites (HD

• M are very small insects not _______ to the naked eye and are the commonest source of allergy in the house. They are ubiquitous and _____ in a warm and moist atmosphere. They _____ very fast and are very difficult to eradicate. Modem houses present ample breeding spaces for them in the form of carpets, curtains, mattresses, pillows, etc.