Mary sent in a warning instead of a question. I thought it might be important to explore.

Here's her e-mail:

Hi,

Just trying to get the word out to all. I had a fire in my home caused by a laptop computer (turned off and unplugged) sitting on my sofa arm. The fire dept. said this was a common way for a fire to start. Please let your readers know the batteries stay very hot after they are turned off. We were lucky to escape with our lives, but this could happen to anyone.

OK. I'm a skeptic. So the first thing I did was tried to track down some information about Mary's situation. After all, we don't want to be accused of spreading urban legends. She was kind enough to provide her address to I could check on the story. The home was in San Luis Obispo.

She also mentioned this:

Now the Dept. of Consumer Affairs is also looking into this fire for faulty batteries and batteries that are pirated. Many computers have been recalled due to this matter.

A quick search turned up a couple of articles:

http://media.www.mustangdaily.net/media/storage/paper860/news/2008/03/13/News/Fire-Forces.Students.Out.Of.Home-3272347.shtml

http://www.sanluisobispo.com/breakingnews/story/306886.html

The next step was to check in with the fire department, since both articles at the time said the cause was under investigation. Since it happened back in March, I thought we could get some input on the likely cause — and prevention.

I reached John Madden, fire investigator for the San Luis Obispo Fire Department (he also happens to be a former Ventura County resident). Apparently, there's still more investigation going on, but here's what he had to say:

The fire started in the area where a laptop was sitting on a blanket on the couch. Madden said material was recovered by a private investigation firm that sent it for lab testing. That testing is still in progress.

Until the lab testing is done, all he can say is that the fire came from that area. But fires have been started by laptops before.

Madden said typically what happens is that the battery gets warm, doesn't have the ventilation needed to cool off and the battery overheats.

There was all of that news of exploding laptop batteries not too long ago. In case you missed it, here's a refresher:

In 2006, HP, Apple, Lenovo, IBM and Sony recalled laptop batteries because they could start fires. In 2007, Lenovo, Acer and Toshiba recalled laptop batteries because they could start fires. This information is from the U.S. Consumer Product Safety Commission.

Some companies announced the recalls were due to a fire hazard, while others said they were because of previous fires. Those stating reports of fires said they had involved minor burns and minor property damage.

We're not talking a small number of batteries here. Demand for laptops has outstripped desktops in recent years and a lot of laptops means a lot of batteries.

In 2007, Toshiba recalled about 1,400 units, Acer recalled about 27,000 units and Lenovo about 100,000.

Even those numbers are smaller than some recalls. In 2006, Apple's recall affected about 1.1 million battery packs.

So what do you do?

First, make sure you don't own a laptop that has one of the recalled batteries. You can go here to search for the recalls. If you search for "computer equipment," they'll show up:

http://www.cpsc.gov/cgi-bin/prod.aspx

Then there's a little bit of common sense.

Here's what Madden suggests:

In the case of the San Luis Obispo home, it could turn out that the blanket was the culprit. That's because it gets pushed up against the laptop and doesn't allow the air to circulate properly.

"The blanket encased it to where it had nowhere for the heat to go," Madden said.

He suggests users make sure their laptops are elevated on a hard surface so the air is able to circulate and dissipate the heat from the battery. If the screen is on and pulling power from the battery, that can make it work even harder, he said.

Anything that has a motor and generates heat has to have the airflow around it to move the heat away, he said.

PC World had a good piece on laptop battery safety back in 2006 that cautioned against getting too worked up about this. Realize that the cases of laptop battery crisis are few — but also realize there are things that can be done to be safer and not become one of the rare statistics:

http://www.pcworld.com/article/id,127029-page,1-c,notebooks/article.html

That's the article. Here are the tips:

http://www.pcworld.com/article/id,127031-page,1-c,notebooks/article.html

One suggestion: Get a laptop "lapdesk" where it sits when on your lap. This tends to lift it up a little and keeps your legs from getting uncomfortably warm when you're working on the couch. I use one for my laptop at home and the laptop pretty much stays on it all the time — even when I'm working at my desk.

I hope this was helpful. Any other suggestions out there? Please feel free to pass them on.

And if you have questions, cautionary tales and other column ideas, please send them my way at abruce@VenturaCountyStar.com.