I received this very interesting dryer-vent story from Steve L., who lives in Southern CA with a seemingly harmless variety of small wildlife. He shared this tale in the hopes that other people will be spared the olfactory misery he had to suffer.
The other day, I found a small mouse in my side yard where our dryer vents. I chased him from his hiding place and thought I had him cornered next to some recycling boxes near the dryer vent. I moved the boxes a bit to find that he had made a little bed out of vented dryer lint. Then in a flash, he darted toward me a few inches and then hopped right up into the dryer vent (the dryer was not on at the time).
I had never looked at the workings of this vent because it has one of those angled covers that directs the air down. I didn't want the mouse setting up shop in there so I ran in the house and turned the dryer on a minute, hoping to scare him out. I went back outside and saw no sign of him. I figured he probably ran away or, worst case, would crawl out when he got hungry.
That must have been a couple days ago. Well, today our laundry room really started to stink. I immediately suspected the worst. I pulled the dryer out and disconnected the few feet of flexible metal duct between the dryer and the wall.
I gingerly carried it outside. I looked inside and what do you know, a dead mouse sitting right in the 90-degree angle fitting that was attached to the back of the dryer. That mouse died within an inch of the inside of our dryer.
Here's how it all happened: I discovered that our exhaust vent has one big flap under that external angled cover. Years of lint had propped it open by about half an inch. I figure that little bugger was able to jump up nose first into that half inch opening and squeeze himself inside. His big mistake was crawling too far inside. The inside flexible ductwork followed an upside down U pattern. I think he was able to crawl up the incline from the hole in the wall to the top of the inverted U but then fell down the longer other side. He was not able to climb back up from the floor level where the exhaust exits the dryer to the top of the inverted U. Tough luck.
That duct has been thoroughly scoured and reinstalled and everything is back to normal. I'm now highly motivated to check that exhaust vent every week when I take out the trash. I also changed the course of the flexible ductwork. It now follows more of a C pattern, which hopefully won't be as challenging for any future invaders.
I have found that it is often best to vent fans and dryers through the roof. I urge you to watch this video of mine to see how easy it is to install the correct vent-cap flashing on a roof. Have no fear - if done right you will have no leaks.