By precisely matching air and gas proportions (stoichiometric ratios), the SunTwin Series of high-intensity, two- stage infrared heaters achieves optimal combustion in both operating stages, the manufacturer says. The heater can be powered by natural gas or LP/propane gas. Models are available with 50,000 to 200,000 Btuh inputs for natural gas and 45,000 to 160,000 Btuh for LP/propane gas. Features include seamless, no-weld construction and rugged, 16-gauge, corrosion-free, aluminized steel main frame, the manufacturer says. The complete ceramic burner assembly has a lifetime warranty.