A dryer vent is much more important than most homeowners realize. A properly installed dryer vent, using the right materials, practically eliminates poor dryer performance, increased wear and tear on the appliance, and the very real fire hazards that go hand in hand with poor vent installation. For all these reasons, it's important to know the ins and outs of this often overlooked home improvement.
Rule #1: Always Run Your Dryer Vent to the Outdoors
Unfortunately, one of the biggest mistakes homeowners make, and installers try to get away with, is venting dryers into basements, crawlspaces, attics, or garages. This is a very bad idea! For starters, it makes for a big mess: dryer lint everywhere. But from a safety standpoint it's also really the pits. By blowing fine particles of cotton and polyester into an area that is rarely cleaned or maintained, you drastically increase the risk of fire. It's akin to packing your attic with kindling and then hoping no one lights a match. And from a moisture standpoint, it's a bad call as well. The increased humidity in these enclosed areas makes for the perfect breeding ground for both mold and mildew to develop.
Rule #2: Never Use Plastic Vinyl Dryer Vent Hose
One of the most common mistakes homeowners make when venting their dryers is to use the economically attractive plastic vinyl vent hose. Again, this is a fire waiting to happen. Lint collects in vent hoses regardless of the material you use, but if the dryer overheats and the lint ignites in a vinyl tube, the hose is going to go up with it and the house often follows. By installing steel tubes and aluminum hose, you decrease friction within the tube (meaning less lint buildup to start with), and you provide a fire barrier between a lint fire and the rest of your residence.
Rule #3: Perform a Dryer Vent Cleaning Once a Year
Perhaps by now you're sensing a common theme throughout: lint accumulation, wherever it is, is bad. It cuts down on the efficiency of your dryer, will wear it out sooner, and worst of all, it presents a huge fire risk. The only way to ensure lint won't ever be a problem is to perform a dryer vent cleaning at least once a year. A vent brush is the tool of choice, though many homeowners choose to hire this job out. Consider adding this chore onto your annual duct cleaning. Most cleaning services will be happy to perform this necessary upkeep as part of a larger routine maintenance call.
Rule #4: Not Just Any Vent Will Do
The final thing to take into consideration is the type of outdoor vent you want to purchase. There are two main considerations to entertain here. First of all, all the lint has to get outdoors. Secondly, you don't want any critters, or weather, using your dryer vent to get in. In order to meet all these requirements, look for a four inch vent with louvered doors if you're venting out the side of your home, and be sure to get a rain proof vent cap if you're venting out the roof.
Remember, proper dryer vent installation isn't a laughing matter. In fact, it can easily be a life or death matter. That being the case, make sure your dryer is venting properly, and that your vent is built from the proper materials. If not, talk to an appliance repairman or other contractor about coming in and doing the work necessary to get your dryer venting as it should.

Matt Goering, formerly a carpenter and house painter, is a freelance writer for the home improvement industry who has published over 600 articles.