**1. Introduction**

Clean air is a basic requirement for life and healthy living. The quality of air in homes, offices, schools, day care centres, public buildings, health care facilities and other private and public buildings where people spend over 80% (3/5) of their time daily is crucial for healthy living and people's well-being. The National Health and Medical Research Council (NHMRC) defines indoor air as 'air within a building occupied by people of varying states for a period of at least one hour' (NHMRC, 1996). Buildings covered by this definition include homes, schools, restaurants, public buildings, residential institutions, offices, etc. (www.arf.org.au)

Indoor Air Quality (IAQ) is an increasing concern in the world today. In fact, the mere presence of people in a building can significantly alter indoor air quality. Indoor air pollution is present in virtually every indoor space, with the exception of strictly controlled and sterile spaces in pharmaceutical, medical and research facilities. Indoor pollutants may originate from human activities, building materials and carpets; they may also penetrate from outdoor environments by forced ventilation, diffusion or infiltration [8]. Humans are inevitably exposed to these pollutants, considering the amount of time spent indoors, but the influence of the pollution on human health may vary, depending on age, sex, nutritional status, physiological conditions, and individual predisposition.

There is increasing evidence linking indoor air pollution to increased risk of respiratory tract infections, exacerbations of inflammatory lung conditions, development of chronic obstructive lung disease, cardiac events, stroke, eye disease, tuberculosis, cancer and hospital admissions especially in women and children who are the most exposed [40, 54, 59, 63].Acute Respiratory Infections (ARIs) are responsible for one-third of hospital admissions and 20%–30% of deaths among children under 5 years [19, 48] in developing countries.

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However, information regarding IAQ in Nigeria is scanty. Aside from the data collected by a few individuals and corporate organisations at scattered locations, there is no comprehensive and empirical database on the magnitude of the health risks and deleterious effects associated with exposure to poor IAQ by occupants in different built environments and the general population in Nigeria.
