ProFire SBR-5 Series is compatible with boiler types such as firetube and watertube. The burner series is capable of less than 5 ppm NOX emissions with flue-gas recirculation (FGR). Designed for use with applications where strict emission levels must be met, the burner line includes a natural gas fuel option from 10.5 to 42 million BTU/hr. Also, it is capable of firing ASTM 2D-S15 (ultra-low sulfur diesel) as a backup fuel at NOX levels below 40 ppm. The burner has a unique fire head design to achieve controlled combustion with 3 percent O2 achievable for all firing rates. It provides up to 6:1 turndown on natural gas.