In mid-June, I had a major fire at one of my complexes. Fortunately, it only burned out one unit. I got very lucky because a chain of circumstances led to unusually rapid response from both Police and Fire depts.

It seems that the fire started in the vent fan in one of the bathrooms. According to my service records, that fan was cleaned and lubed about two years prior, before the current tenant moved in. According to the tenant, it had been working normally the night before the fire. According to the tenant's son, it began making a grinding noise minutes before the fire started.

Now, I have been scratching my head over how a vent fan could start such a fire. The fan housing was plastic, so it burned and the fire was quickly in the attic. Fires tend to destroy a lot of clues, so we never figured this one out.

We pulled sample inspections on vent fans in the rest of the complex, and didn't find anything unusual. We inspected about a third of the fans in the place.

Today, since I am very shorthanded right now, I was running service calls. I was working for awhile in an apartment in that complex that came open last weekend; we have someone waiting for it so we have to turn it immediately. While I was working in there, I took the cover off the vent fan in the bathroom.

Bingo! This fan was covered with lint, probably as much as a quarter inch all over the motor and inside the housing. I have no clue where the lint came from; this is an upscale property in an upscale neighborhood, and we seldom have sanitation problems with our people, and in the majority of cases we return at least part of the deposit (meaning cleaning, damage and repair expense due to tenant negigence is minimal).

However it got there, it was there - and in quantity. The fan motor (which ordinarily should be at most very slightly warm to the touch, after extended running time) was almost too hot to handle. I took it down, disassembled it, cleaned it out, lubed it, and put it back. Then it ran cool.

So, what caused the fire in June is this: for some reason, a lot of lint and dust gets into the environment in the apartment. The vent fan is run a lot, and it pulls this lint/dust in. Some deposits on the fan. Eventually the fan overheats, blows a spark as the motor fails, and ignites the lint.

This idea had never occurred to me before, the more so because I cannot account for where the lint came from.

As soon as I have enough staff back in place (next week, I hope), I'm going to start an inspection program for all our vent fans in every location.

I'm also going to pull all the vent fans in my house and look at them.

I've never heard of this problem before, but it bit me hard, and I found another situation that was developing.

Now, later model vent fans have a thermal fuse in them; if that motor gets too hot the fuse blows. However, I don't know if ALL vent fans have this feature; the complex I have been discussing was built in the mid '70s and it doesn't have them, and my house was built in 1992 and IT doesn't have them in the vent fans. So, I don't know if these fuses are common or not.

You might want to pull the covers off your vent fans and have a look. After all, what'll it cost you to do that?

About the Author: Jim Locker is a technical guy who has done a lot of real estate investing and landlording. The experiences he writes about and advice he gives are either first hand, or in answer to specific questions posed by others. He is commonly known as jiml8 around the internet.