Available in both natural and propane gas, the new PTS/PTU Series Tube Heaters from Space-Ray use positive pressure to push products of combustion through the heavy-duty calorized aluminized or alumatherm steel combustion chamber. The tube heaters include patent-pending Tube Integrity Safety System for additional safety. Capacities for the PTS/PTU Series range from 40,000 BTU/hr to 200,000 BTU/hr.