Peter -
Are you sure it is the monoxide detector that is kicking off, and not the LP/propane detector? I suspect the latter since you can smell gas - carbon monoxide is odorless. What year is your TM?
The propane detector can be kicked off by any number of things, not just carbon monoxide. For example, I seem to recall that hair spray is among the favorites.
Just for interest, I will mention one thing that you can be sure of - if there is no flame, there is no monoxide, since monoxide is a product of combustion. But something is kicking off the detector, and it sounds like you are getting a quick shot of raw propane before the automatic valve closes. And it will close.
I don't know how to fix the flame-blowing-out problem, but you might try securing a piece of aluminum window screen (or fiberglass screen behind a sheet of 1/4-inch or 1/2-inch galvanzed hardware cloth) to the inside of the vent louvers. The idea is to break up the stream of air.
Finally, have you checked the quality of the flame, using the instructions in the water heater's manual? Or there is a good video at
If the flame is too lean (too much air), it will be on the verge of blowing itself out, and it doesn't take much of a puff of wind to finish the job.
Let us know.
Bill
[By the way, this thread belongs in the Appliances forum. I will move it there shortly, and you will lose access to it since your Sponsorship has run out.]