High-space heating units, also known as high-space circulation heating equipment, high-space heating systems, or high-space HVAC units, have various names with diverse origins. We only need to familiarize ourselves with a few common terms, such as the air-to-air heating and cooling units based on their working principle. They are also referred to as high-space unitary systems, high-space heating unitary systems, high-space heating systems, high-space air heaters, large-space heating units, or high-space heating and cooling units. These are product names frequently used in both industrial and domestic applications.