CHAPTER ONE
1.0     INTRODUCTION
        Air supplies us with oxygen which is essential for our bodies to live. Pure air is a mixture of gases that are invisible, colorless and odorless consisting of 78% nitrogen, 21% oxygen and other gases as well as varying amounts of water vapor (Murray et al., 1995). This pure air can become contaminated in various ways affecting humans, plants and animals. Air pollution is the introduction into the atmosphere of chemicals, particulate matter or biological materials that causes discomfort, disease or death to humans, damage to other living organisms including food crops. Both indoor air and outdoor air can become polluted by pesticides. These pesticides contain active and inert substances such as cyclodiene which is associated with symptoms such as dizziness, headaches, weakness, muscle twitching and nausea (Hays et al., 1995).
        Good indoor air quality (IAQ) is important for all of us; most people spend 90 % or more of their time indoors. Most of this time consists of the hours spent at home or at work, while school age children spend 20 % of their time in schools (Clench-Aas et al., 1999). Good IAQ consists of many aspects; it is an interaction of a functioning and efficient ventilation and the lowest achievable amount of chemical, inorganic or organic and microbial compounds which should not evoke symptoms in the occupants (Spengler et al., 2001).
       Microorganisms such as bacterial and fungal spores are almost always present in the air. The quality of indoor environment, however, is not easily defined or readily controlled, and can potentially place human occupants at risk (Jaffal, et al., 1997a). Airborne transmission is one of the routes of spreading disease that is responsible for several nosocomial infections (Claudete et al., 2006).
        Exposure to bio-aerosols, containing airborne microorganisms and their by-products, can result in respiratory disorders and other adverse health effects such as infections, hypersensitivity pneumonitis and toxic reactions (Gorny et al., 2002; Fracchia et al., 2006).
        Indoor air quality is a term which refers to the air quality within and around buildings and structures especially as it relates to the health and comfort of its occupants. Indoor air can be polluted by various compounds such as carbon monoxide, volatile organic compounds (VOCs), particulate matter and microbial contaminants (moulds, bacteria, viruses) and any action that introduces harmful contaminants into the air within the building. The concern for quality indoor air is necessary especially in institutionalized settings that accommodate a large number of people such as hospitals, nursing homes, prisons, schools, family because contaminated air can cause both mild and severely irritating health conditions (Tambeker et al., 2007). The quality of air in hospitals in relation to microbial contamination at a given time period is determined by the quality of air entering into the building, the number of occupants in the building, their physical activities and resultant aerosol generation, human traffic and the efficiency of ventilation (Adebolu and Vhirterhre, 2002).