Refrigeration compressors and air conditioning compressors provide air conditioning, heat pumping, and refrigeration for large-scale facilities and equipment. They use compression to raise the temperature of a low-pressure gas, and also remove vapor from the evaporator. Most refrigeration compressors (refrigerant compressors) are large, mechanical units that form the heart of industrial cooling, heating, ventilation, and air conditioning (HVAC) systems. Many air conditioning compressors are also large-scale mechanical devices; however, these compressors are designed specifically for air conditioning systems and do not provide heating or ventilation functions.