Section 431.246 - Energy conservation standards and their effective datesA unit heater manufactured on or after August 8, 2008, shall:
(a) Be equipped with an intermittent ignition device; and(b) Have power venting or an automatic flue damper. An automatic vent damper is an acceptable alternative to an automatic flue damper for those unit heaters where combustion air is drawn from the conditioned space. 70 FR 60418 , Oct. 18, 2005, as amended at 71 FR 71374 , Dec. 8, 2006