If it's been a while since your dryer's vent has been cleaned out, you'd better call to have it done again -- and then have it done regularly. Not only can a buildup of lint create efficiency problems and fire hazards, but it can contribute to the presence of animals in the vent. Here's a look at why the animals get in there and what you can do to keep them out, or at least reduce the likelihood that they'll want to stay.
Cozy, Warm Nests
Dryer vents are nice, warm, cozy places that are well-hidden from predators. There's also this handy nesting material -- lint -- that shows up on a regular basis. The vent and hose connected to the dryer are thus desirable places for small animals like mice who want to stay safe. Birds are also attracted to the vent openings, which often provide sturdy ledges where they can build a nest.
The hoses in particular can become traps for those small animals. Too much lint and too much heat, as well as vertical drops that can injure and kill an animal if it falls down one of them, can result in dead animals stinking up your home. The dead animals can then block the hose and vent, reducing the dryer's efficiency and increasing the risk of fire from excess lint.
Screens and Fire Risks
One solution that may come to mind is to put a screen across the opening to the vent, much like you'd place screens across attic or crawlspace vents to keep animals out. However, because the vent has to let lint come out, the screens can serve as obstacles themselves, blocking lint from exiting and creating a clogged vent.
Hose Length and Vent Placement
Instead of a screen, you can try to keep hoses as short as possible -- don't let installers put in hoses that twist, turn, and loop because the hoses are too long. If you're installing a new hose yourself, cut it down to fit. Also place vents in areas that are clear of debris and away from all plants, tree branches, wood piles, and anything else a critter could use to climb into the vent.
Despite all of these precautions, animals can still get in; birds can still fly into even isolated vents. Regular vent cleaning and hose inspection is your best way to prevent problems. Even if an animal is attempting to build a nest, the cleaner will be able to spot it and remove it.
If you want to find out more about dryer vent and hose cleaning, contact a service that specializes in appliance duct cleaning like Home Plus Duct Cleaning. The staff can describe their process and show you what they look at, and you can discuss ways to block access by animals.