Some new dryers boast a feature to alert you if your lint duct is blocked. Chris Olsen shows you how it works -- and what you can do to reduce the risk of a dryer fire at home.

Lint-filled dryer ducts cause about 4,500 fires a year in North America. Some are fatal. In September 2008, mother of two Gena Brown of Lexington, Massachusetts was overcome by heat and smoke. Fire investigators blamed a blocked dryer duct.

There's a new feature on some dryers that could help prevent fires. But does it work? On the LG dryer it's called "Flow Sense" and on Kenmore machines it's a "Check Vent" indicator. The manufacturers say these will sense if a dryer's vent is blocked. While both companies say this will improve performance, neither is calling it a safety feature.

Consumer Reports tested to see if this feature could alert you to a blocked dryer vent.

"We tested each dryer by blocking the vent completely, and then operating it with a full load of wet clothes," the magazine's Jim Nanni said.

Turns out, the results were inconsistent. The four orange "Flow Sense" bars clearly show that the vent is blocked.

But other times, despite the fact that the vent is completely blocked, there is no signal at all, and the dryer continues to run for more than an hour.

"These tests, though limited, show that these indicators can't be relied on to alert you to a blocked vent," Nanni said.

So no matter what dryer you have, Consumer Reports says use a metal dryer vent and clean it regularly.

Flexible ducts made of foil, or plastic, pose the most serious problems. They can sag, letting lint build up at a low point.

If you're in the market for a new dryer Consumer Reports says the Kenmore 800 series is a best buy for about $500. If you need a large capacity consider the Kenmore Oasis for $50 more -- it's highly rated and is packed with usable features.

Among full-sized stackable dryers, the LG DLE 2701 is tops in Consumer Reports testing, and costs $1,100.

It scored "excellent" in overall performance for drying, capacity and for noise level.

Its automatic dryness control recognized already-dry loads and turned off the dryer.

Consumer Reports recommended dryers use a moisture sensor to get the job done with the least wear and tear on your clothes. So when you use your dryer use the automatic settings, not timer settings. And, new or old, make sure to clean your lint trap every time you use your dryer. It's an easy habit to develop.

With a report from CTV British Columbia's Chris Olsen.