Health and capacity for work of a human to a large extent depends on indoor microclimate in his dwelling and working areas, where he spends most of his time. On the average, a person consumes 15 kg of air every day. How pure the air is, is it foul, warm or cool depends on engineering systems, specially elaborated for creation of comfortable indoor microclimate. Such systems include: ventilation system, also systems of heating and conditioning. Combined systems of heating and ventilation create sufficiently comfortable microclimate. Air-conditioning system represents a system of more capacity. Main advantage of air-conditioning system is that besides heating and ventilation there is a possibility to create comfortable indoor microclimate (comfortable temperature). The system can heat, cool, filter, dry and moisten air apart from metrological changes. You will always have comfortable climate indoors notwithstanding 40 C heat or 0 C cold outside.