Why is Lead Used in Some States and Not Others

The two common way to seal vents is with lead or a rubberized grommet. The grommet is inexpensive and works fairly well, so why would anyone use the more expensive lead? The answer is the weather. Most, if not all, flexible plastics will harden over time when exposed to UV light and heat. In the Southern and Southwestern states you have a ton of both, along with a lot of rain. So flexible grommets, when they harden, crack and then leak like sieves.
Lead doesn’t do this. Lead sealed vents should last the life of the house. They dont fail due to light and heat. However, they are prone to being eaten by squirrels which causes them to leak. Also borderline states, such as Georgia, simply dont want lead in their landfills, so its use is limited.
Lead is also used in areas by tradition, such as St. Louis, or because they can be made large for large vents, such as Chicago area. In the end its superior to the rubber, but limited in its use to these areas generally for the reasons above.