The inside of your dryer collects lint and if not cleaned frequently can cause a fire. My first post isn't meant to create drama but more to create awareness of the danger of your dryer catching fire.
A customer came in a couple of months ago and said, "she smelt fire when the dryer was on". I commended her on not using the dryer. She bought a dryer and we delivered it and picked up the old one.
Here's what we found. The dryer had caught fire and the inside of the box was burnt. In addition, there was lots of lint and the dryer wheel had broken. This damage had also allowed small socks and items to fall down inside the dryer. These three things had caused the fire.
To summarize, if you smell fire when drying your cloths stop the dryer and unplug it and call a qualified technician. It can become very serious.
Get in the habit of cleaning the dryer filter with each load you dry.
I'm starting to sound like your Mother but one more thing to keep in mind, if you use fabric softener sheets, you will clog up your filter and not even realize it. After a couple of months clean it with hot soapy water or until the water pours through the screen. This will insure a good air flow over the filter screen and catch the lint from the dryer.