The National Fire Protection Association estimates a nationwide average of 12,900 home dryer fires per year between 2012 and 2016. On average, dryer fires are blamed for 10 deaths, 360 injuries, and $211 million in property damage annually.
Lint is very easy to burn, very flammable and doesn't allow for adequate air flow in the dryer. You're working with high temperatures in a dryer, so build up over time causes a real safety risk.
Experts say the biggest warning sign that you have lint build-up is if your dryer is taking longer than usual to dry your clothes. You should clean the lint filter before and after each load of laundry. Don't forget to clean the back of the dryer where lint can build up. The frequency of cleaning your vents usually depends on the number of loads you typically do, but don’t overlook this step. In addition, you should clean the lint filter with a nylon brush at least every six months or more often if it becomes clogged.
If your dryer does start smoking leave the door shut, try to turn it off or unplug it, and get away. If it's in the laundry room, close the door and call 911. The worst thing you can do is open it the dryer door. It gives it more oxygen and then you will have a bigger fire.