fire damage in water heater area

[mtpalms]

We got our '71 Safari home yesterday and started ferreting through it in the way new owners will with a new toy. Before we bought it, we checked out all the appliances in the usual manner, through the access doors, and all looked A-okay.
At home, we started opening doors, pulling out bins, and peeking under mattresses and cushions to find all the hidey holes, spare change, etc. To my horror, when I lifted the streetside twin mattress at the bathroom end, the was a huge burned area in the corner. The mattress didn't show any evidence of scorching, nor were there any other traces of recent fire damage that we could see. It appears that there had been a fire in the water heater compartment at a point in time.
We suspect that either A) someone was doing some maintenance, turned on the gas, then lit a match, and created the FWUMP! effect. Or B) left the gas and the water heater on while tooling down the road, causing a flare up, which extinguished itself by oxygen deprivation.
Anybody more knowlegeable than us have any idea what might have caused this, and what to look for as far as damage that may compromise the heater's safety?
This probably happened long ago, as there are no smokey smells, or soot evident anywhere, just a burned area in the plywood.

[overlander63]

Originally Posted by mtpalms

We got our '71 Safari home yesterday and started ferreting through it in the way new owners will with a new toy. Before we bought it, we checked out all the appliances in the usual manner, through the access doors, and all looked A-okay.
At home, we started opening doors, pulling out bins, and peeking under mattresses and cushions to find all the hidey holes, spare change, etc. To my horror, when I lifted the streetside twin mattress at the bathroom end, the was a huge burned area in the corner. The mattress didn't show any evidence of scorching, nor were there any other traces of recent fire damage that we could see. It appears that there had been a fire in the water heater compartment at a point in time.
We suspect that either A) someone was doing some maintenance, turned on the gas, then lit a match, and created the FWUMP! effect. Or B) left the gas and the water heater on while tooling down the road, causing a flare up, which extinguished itself by oxygen deprivation.
Anybody more knowlegeable than us have any idea what might have caused this, and what to look for as far as damage that may compromise the heater's safety?
This probably happened long ago, as there are no smokey smells, or soot evident anywhere, just a burned area in the plywood.

First, congratulations on your "new" trailer!
Look for evidence of a repair to the gas lines and pilot area. If there is none, you should check the area with a propane detector, with the propane on, and the pilot flame OUT.
Check for wasp and mud dauber nests in the combustion tube, look for cracks and holes in the tube, and exhaust.
If this is your first time lighting off one of these things, it would probably be money well spent to take the trailer to an RV dealer, and have them go over the propane system, and make sure everything works, and nothing leaks. Ask to be shown the proper way to light your appliances, they should be happy to show you.
Also, you have a trailer of the same vintage as mine, it would be a really good idea to have the furnace checked for cracked intake and exhaust hoses, mine has them, and the carbon monoxide would likely kill us if we used it. This is high on our "to do" list.
Anybody else know anything else to check?
Terry

[mtpalms]

Thanks Terry.
It isn't our first trailer, and my husband repairs spa and pool heaters, so this isn't completely foreign teritory, but having my mechanic (he's certified to work on RVs) take a look at everything is a good idea (we'd planned on it, but perhaps we should prioritize it). Particularly since you mentioned the furnace, the previous owner did say he replaced a boot on it indicating recent maintenance, but then again he never mentioned the "black hole" under the mattress. Better safe than - well dead, frankly.