Air conditioning can completely eliminate or minimise the effects of harmful factors such as excess heat (conventional, causing an increase in air temperature and radiant); excess water vapour – moisture; gases and vapours of chemicals with toxic or irritating effects; toxic and non-toxic dust; radioactive substances.
The sources of hazardous factors include:
Excessive heat. An adult person in a calm state and under normal microclimatic conditions emits 85-120 W into the environment, of which an average of 20% is by convection, 55% by radiation and 25% by moisture evaporation. The amount of heat emitted by a person varies depending on physical activity and the air temperature in the room. In crowded rooms, heat emissions create unfavourable conditions that have a harmful effect on people’s health and performance.
Moisture emission. The amount of water vapour emitted by the human body at moderate air temperature and light physical activity is 40-75 g/h. At high ambient temperatures, moisture production can increase to 150 g/h. Excessive water vapour in the air can occur in public buildings, as well as in workshops and departments of industrial enterprises.
Gas emissions. The content of gases and dust should not exceed the maximum permissible concentrations in accordance with regulatory documents.
Optimal microclimatic conditions are those combinations of air parameters in the working area that ensure the preservation of the normal functional and thermal state of the body during prolonged and systematic exposure to them.
In accordance with sanitary and hygienic requirements, air conditioning systems should provide the following in the serviced premises
– Set internal temperature conditions;
– relative humidity
– gas composition;
– air purity and mobility.
The most favourable temperature in public and administrative premises should be 20-22°C, with permissible fluctuations in the warm period ranging from 20 to 28°C, and in the cold and transitional periods from 18 to 22°C.
Relative humidity is considered optimal in the range of 30 to 60% in the warm period and 30-45% in the cold and transitional periods. The upper permissible limit of relative humidity is 65%.
In order to destroy the shell of gas emissions created by the human body, it is necessary to organise the movement of the air environment. However, it is unacceptable to excessively increase the speed of the air movement due to the feeling of discomfort and the possibility of colds. At an air temperature of 20-25°C, the permissible air velocity is 0.2-0.3 m/s for easy work.
The condition of the air environment in technological premises is a necessary and often decisive condition for the stable and long-term operation of many electronic devices. One of the requirements for uninterrupted operation of equipment is to maintain optimal air temperature, purity and humidity. These parameters are ensured by air conditioning systems, which are subject to the following requirements: reliability, accuracy of temperature control, maintenance of the specified humidity and dust content.