Heat exchanger units that use steam to produce hot water are known as indirect heaters. The plate heat exchanger should be selected for operation at the minimum pressure to provide the most efficient operation. Accessen plate heat exchanger series covers the simple basics of steam in HVAC systems. Most healthcare facilities and some industrial facilities use steam in processes, such as steam for humidification, sterilizing instruments and possibly steam heat exchangers. Many large cities have central steam distribution systems to downtown office buildings.