Veloci’s Inlet ducting accessories are specific to each heater due to inlet diameter. Be sure to adhere to the inlet ducting maximum length of 20 feet for each heater model (40′ max for the Firestorm400HC) and remember to limit the recirculated air temperature to less than 120°F. Always use an inlet duct clamp to properly secure the duct to the inlet adapter – Part #48.7241.