with the increase in nosocomial infections, evaluating the indoor air of health institutions have gained much attention. understanding the type of microorganisms and their population in the indoor air could be used as index for the cleanliness of the health centres and control of air-borne infections. This book provides information relating to the quality of indoor air in some government health institutions and methods used in determining the microorganisms present in the indoor air of any environment. Bacillus cereus, Chryseobacterium sp, Escherichia coli, Proteus mirabilis, Staphylococcus aureus, Staphylococcus epidermidis, Aspergillus fumigatus, A. flavus, A. niger, Candida sp, Mucor sp, Penicillium sp, Trichoderma sp and Rhizopus sp are microorganisms which in large numbers could pose serious health challenges. They could cause hospital related infections or nosocomial diseases.