Maintenance strategies and spare parts consumption is greatly influenced by the reliability characteristics of system or components under consideration. Any maintenance policies or spare parts planning without considering the reliability characteristics are not optimum. Therefore it is important to study and analyse the reliability characteristics before making decision concerning spare parts and maintenance planning. It is known that the operating environmental conditions in which system is to be operated, such as temperature, humidity, dust, load, voltage stress, etc. often have considerable influence on its reliability characteristics. These factors, in fact affect the failure rate of a repairable system and non-repairable components, but are usually ignored in the reliability analysis. Thus operating environment should be considered as an important factor while making decision about maintenance, spare parts planning, product support, and service delivery strategies. In general, new products are often used under conditions that are not anticipated. It is common to modify predicted life length and reliability characteristics of product by considering the environmental and other factors. The purpose is to incorporate the effect of the environmental factors such as temperature, humidity, dust, voltage stress, etc in reliability analysis.