HVAC stands for Heating, Ventilation and Air Conditioning. The system was developed to regulate temperature and humidity indoors, to provide the circulation of fresh air and to remove odor from buildings.
-heating- there are several heating systems. The most popular and widespread is central heating. It is used mainly in private houses and public buildings.
-ventilation- aims at changing the air, controlling temperature and remove unwanted substances like carbon dioxide, bacteria, smoke, odor, etc. Ventilation is also responsible for exchanging the air with the outside and its circulation in a given room
-air conditioning systems- provide the removal of heat and cool the air. These systems are very popular in countries with warm climate.
Coming back to the problem of mold, there are several issues considering using HVAC. If you suspect that your HVAC system may be contaminated with mold, do not turn it on. In this way, mold spores may enter the air and pollute it. If you are not sure if air conditioning or ventilation system is free from mold, check it thoroughly before turning it on. Sometimes mold fragments are very small and thus impossible to notice.