Clogged vents, ducts, and filters are the primary causes of dryer fires. Usually, this is a result of a buildup of lint, but can certainly be caused by an accumulation of dirt, grass, or anything else that remains after the washing process.
In addition to the lint filter, the outside vent can also become clogged, which prevents airflow and potentially leads to hazardous conditions. Again, this could be a result of lint making its way through the duct and collecting on the screen. However, it can also become obstructed by pesky birds, insect nests, or rodent nests.
How to prevent dryer fires:
1. Make sure it's properly installed
2. Clean lint screen after each use
3. Clean the vent and duct
4. Replace ducts
5. Have your dryer routinely inspected
6. Make sure you are using your dryer correctly