Before you let it gall you, remember that many components have expected lifetimes based on cost analyses made prior to manufacture. I suspect it is possible to design 2500 watt lamps that are internally water cooled, but such a design was determined not to be cost competative.

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I think I will take your suggestion about getting a mechanical contractor and measure the actual air flow at the stack and tell us what has to be done to get them within specifications.

Jerry, it was not really a cost vs design problem. It was designed by someone who was not familiar with the problems. Some of these guys thought a projection booth is nothing more than a small room with a 16mm projector using a 1,000 watt incandescent bulb. There are some contractors that still think all that is needed for a lamp vent is a bathroom fan!

It appears the contractor made some incorrect calculations. A 360 CFM unit was used. Apparently, they forgot to calculate how much airflow was lost in the duct work run, elbows, and reducers.

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At an old theater we have, I wanted to significantly increase the air flow. (The booth used to run carbon, but now has two xenons.) I just replaced the smaller roof fan with a big honking fan, and all was well - got great bulb life.

Some years later, at a newer theater, I wanted to do the same thing. (This theater was designed only for xenon lamps.) After I did it, the air flow was still poor. It had the same size fan and ducts, with the same lamp as the previous theater. It took a while, but finally I figured out why it wasn't working.

Although I had a bigger exhaust fan, I still had the same supply fan. That is; I was trying to pull more air out, than was going in, to the booth. The old carbon booth had two external ducts at each end of the room that went directly to the outside, so air flow "in" was no problem. The new theater had never been designed that way - the only air into the booth was through an AC unit.