Ambi-Rad gas-fired, vacuum-operated ER Series radiant tube heaters fromAdvanced Radiant Systems, Inc.(Fishers, IN) are available in burner rating ranges from 40,000 to 150,000 Btuh in "U" tube or straight configurations in lengths of 20 to 60 ft. Up to 10 burners can be connected to one exhaust fan through an aluminum manifold with only flue to the atmosphere.