Biological hazards refer to organisms or organic matters produced by these organisms that are harmful to human health. These include parasites, viruses, bacteria, fungi and protein. In general, there are three major of routes of entry for these micro-organisms into our body, i.e. through the respiratory system, transmission through contact with body fluids of the infected or contact with contaminated objects. The harmful effects posed to human health by these biological hazards are mainly of three types - infections, allergy and poisoning.Indoor workplaces like entertainment premises, restaurants and hotels, where employees generally work in enclosed areas with central air-conditioning Any microorganism breeding inside the air-conditioning system or cooling towers may spread in the workplace through the air-conditioning system.