In some areas of the country, spiders or small insects have been found to create “flashback” problems.
The spiders spin webs and/or insects build nests in the grill’s venturi tube(s). The web and/or nests can lead to gas flow obstruction which results in a “flashback”—a fire in the venturi tube(s). The grill may still light, but the obstruction does not allow full gas flow to the burner. Therefore, some gas will back up and escape at the venturi shutter. This will ignite, causing flashback, which also could damage your grill.
Cleaning your venturi tubes will require you to remove the burner. Be sure the grill is cold. Open the lid and remove the cooking grids, the porcelain briquettes and the briquette grate. This should give you access to remove the burner.