Most of the homes here in Florida have a split system HVAC system. That means the Condensing Unit, (or compressor) is outside beside the house, and the Air Handler, (or coils) are either in the attic, in a closet inside the house, or some of them are in the garage. The coolant runs through supply  line from the compressor to the coils and returns through the return line back to the compressor. They usually run up the side of the house and into the attic and are covered by a metal cover channel that is basically a big "U". The issue is that if you don't seal the bottom of that channel, it is like a big runway running right up into your attic and your house inviting pests and rodents!

"How are those little pests getting into my house?" You may ask. They should be sealed by the contractor but nooooo... hardly ever! Some pest control companies will do it because the house is infested with, yep... rats or insects. There are several ways to do it, and you have to be certain it is sealed pretty good.

The first thing that comes to mind is the all popular "expanding foam". Well, that works pretty good but rats will chew through that and go right back up the runway! So you have to use a combination of screen, steel wool, or something tough enough to discourage the little fellers. I have found that the combination of course screen and the expanding foam works best.