In the Webster Combustion aggregate dryer burner family, the company offers the HDRA Low NOx burner series—rotary drying. The model HDRA-RF is a register-style total air burner that allows producers to shape the flame by automatically controlling the register vanes to optimally fit their dryer and combustion zone. This flame-shaping capability means the flame will not impinge on material or flights, and CO can be maintained at much lower levels. In addition, NOx levels for the HDRA-RF are significantly lower than typically seen in asphalt applications, according to the manufacturer. It is designed for firing rates from 50 million up to 200 million Btu/hour. Its turndown rates are up to 10 to 1 on gas firing; up to 8 to 1 on oil firing, according to the manufacturer.