In recent years there has been many stories about dryers catching on fire*. Should we be concerned? Yes of course. We should take seriously anything that may put our family at risk.

Was the problem the dryer? Rarely.

After investigating it is usually determined to have been the venting within the home catching on fire, and not the dryer.

The drying process

When clothes are being dried inside your family dryer there are two processes happening. Firstly, heat is applied to the air inside the dryer drum as it turns. This raises its internal temperature to approximately 165 degrees Fahrenheit and causing moisture to be driven out of the clothes by evaporation. Secondly, a constant flow of air is passed through the clothes. Surprisingly, the real trick to efficiently dry clothes is not the heat, but rather this vast volume of air.

Most people think the purpose of venting is to push the heat and lint outside. Actually, its primary purpose is to dump the moisture outside the home. This job is accomplished easily when the dryer is near an outside wall.

The venting pipe

In many new houses the laundry room is located in the centre of the home, close to the family room or kitchen. If located upstairs it is often between the bedrooms, to allow easier access to laundry. Easier access, but the distance from the dryer to an outside wall is substantially longer. This leads to the crux of our problem. The venting is either too long, or has become restricted.

It is more difficult to push air down a long venting pipe than a short one. When the venting is too long the excess air can cause the venting to misbehave. This results in the moisture and lint collecting in the venting, rather than being dumped outside.

Taken to extremes lint can block the venting closed. When this happens it can cause the dryer to overheat. The normal drum temperature of 165 degrees Fahrenheit can quickly shoot up to 300 degrees Fahrenheit or higher. It may even get hot enough to allow lint in the venting to ignite.

For this reason manufacturers now suggest a maximum venting length of 15 feet. Excluding the first two elbows.

True venting length

If you want to know the true equivalent length of dryer venting, calculate the following:

1. Measure all the straight lengths and add them together

2. Count the number of turns or elbows, and multiply this number by 4

3. Add up the totals of steps 1 and 2

Example 20 feet of venting with 4 turns would actually be:

20 feet + 4X4 feet = 36 feet

Dont be surprised by the true equivalent length of your venting. In modern homes it can be substantially longer than the manufacturers suggested maximum.

Watch for these signs

If the blockage becomes critical the dryer will stop doing its job properly. As a homeowner watch for the following signs that the venting may be starting to block.

1 Clothes coming out wet
2 Excess lint left on clothes at cycle end
3 Inside of dryer feels wet
4 Taking too long to dry a load
5 Clothes very hot at end of cycle
6 Electrical consumption greatly increased

Since you can't move the laundry room the best thing you can do is be aware that the problem exists. Consider taking down the venting and cleaning out the lint buildup during your annual spring-cleaning. Also, regularly walk outside and check the vent cap where it exits your house. Remove any lint buildup and make sure the flap moves freely.

If for any reason you suspect a venting problem turn off the dryer, unplug it, and call your appliance service company. Tell them your concerns, and ask for their help. As the old saying states, "better safe than sorry".

* There are an average of 14,500 dryer fires every year. National Fire Prevention Association