Separated Combustion Unit Heater (PTS/BTS, HDS/HDC) – Separated combustion unit heaters obtain 100% of their combustion air from outside, ensuring that nothing but clean, fresh air is burned in the combustion chamber. This fresh-air supply reduces common concerns about maintenance, performance and durability, especially in dusty, dirty or humid applications. It also increases the overall heating efficiency. Available in commercial (PTS/BTS; 150,000 to 400,000 Btu/hr) and residential Hot Dawg sizes (HDS/HDC; 30,000 to 125,000 Btu/hr), with both blower and propeller units available. Learn more about our Commercial Separated Combustion Unit Heaters (PTS/BTS) or our Residential Separated Combustion Unit Heaters (HDS/HDC).