JOE <> The problem here is the fact that you probably won't be producing enough heat to justify the cost of a heat exchanger, in relation to how much heat you can gain from it... Depending on your lamp size, the heat it produces (at the exhaust) is about equivalent to a good sized hair blow dryer, unless you have something in the range of 4k watts, or larger... Since the heat exchanger isn't nearly 100% efficient, you can recover only part of that, and I doubt that what you will recover will justify the cost of recovering it... Now, I am going to make a confession, and you gotta swear you won't rat me out... I built my own lamphouse conversions, and the last item on the lamphouse is a fairly quiet blower which normally exhausts the lamphouse into a gravity/draft system dumping into outside atmosphere... In cold weather I loosen the clamps at the top of the flex connecting hoses, and install plugs in the gravity duct which have a bracket to support the exhaust flex, and dump all the heat into the booth... I utilize 100% of the heat from the lamps... Is this safe?... Well, the booth is fireproof, having been built back in the nitrate days (I finally did away with the fire drops about 20 years ago, when the state finally admitted they weren't necessary any longer) so there is no fire danger (which is questionable IF there is, under ANY circumstance, with xenon)... The lamps are supposidly ozone free, and it hasn't been that long ago that ozone producing lamps were sold to reduce bacterial contaminations and odors, and touted as healthful... Every other week something that has been "good" for you, is NOW declared "bad" for you, then reversed again, so what can you believe... I suspect that even IF there is a small amount of ozone produced, it isn't that unhealthy... Besides, I am a 3 pack-a-day smoker, and have worked with asbestos based brake linings, and clutch facings, hydrocarbon based carburator cleaner, fiberglass, lacquer paints, leaded paint, leaded gasoline, formaldehyde and hundreds of other things which are NOW declared to be health hazzards... To be sure, something will eventually kill me, but I doubt that it will be the short time exposure to the exhaust from a Xenon lamphouse... In the meantime, I supplement the heat in my booth with some "free" heat for a couple of months a year, and it feels damned good!...