The RE series mix air units offer the most efficient available method to heat mix air. Direct fired make up air heaters may be considered to be 100% efficient because no heat is vented to the atmosphere. The theoretical 100% efficiency should be reduced to 92% due to water vapor being formed as a natural part of combustion. With heating capacities up to 11,000 MBH and air capacities up to 100,000 CFM. They are also available in variable capacity, dual capacity, air curtain, and/or heat recovery configurations