Built-up lint inside dryer cabinets causes more than 15,000 fires every year. Lint escapes through tiny gaps around the edges of the dryer drum and falls into the cabinet, especially when the exhaust vent or vent cap is clogged and airflow is restricted. The lint can get ignited by electric heating elements, gas burners or even a spark from the motor, and the flames then travel through the lint-lined exhaust vent. To make sure this doesn't happen in your house, check the exhaust vent and the inside of the cabinet frequently.
To clean the exhaust duct, shut off the gas and unplug the dryer, then pull the dryer away from the wall and disconnect the duct from the dryer. Use a brush and a vacuum to remove the lint in the duct. If you have a flexible duct (especially the plastic type!), replace it with rigid metal duct.
To clean inside the dryer, unplug it and turn off the gas, then open either the top or the front. The procedure is the same for gas and electric dryers. For dryers with a top lint filter and a solid front panel, remove the lint filter and take out the two screws on the side of the filter opening. Pull the top forward (Photo 1). Disconnect the door-switch wires in the front corner, remove the front screws and drop the panel forward (Photo 2). The drum will tip as the panel drops, but this won't damage anything. Just hold it up while you clean.
Brush and vacuum under the drum and at the top and back of the dryer. Clean thoroughly around the heating element, but work gently around wires and mechanical parts. Use a long brush to clean the vent, then vacuum it from the top and back (Photo 3).
Finally, reassemble the dryer. Put the front into the drum and lift, then drop the front into the catches near the bottom while holding it tight against the sides. Reattach the front screws and wires, then set the top back down.
For dryers with a removable front panel, release the metal catches (or remove screws) and pull the panel off (Photo 1). Remove the screws that hold the vent in place, then clean out the lint with a vacuum and brush (Photo 2).