Alexy asked about my position on U/V hoods.
It is pretty much the same as with any other "gizmo" that is installed in the path of grease vapors being evacuated from a building. They can have a place but with conditions.
These devices (and others) are maintenance-dependent. Therein lays the most noticeable flaw. Our society has an overwhelming disregard for the importance of maintenance. (That reminds me, I am a couple months behind in replacing the water filters in the house).
It is not worth getting into the tired "rage against society" argument. Suffice to say that these units are an obstacle and an opportunity to exhaust cleaners. They will increase in use, so learn more about them. The knowledge you can provide to your customers is your greatest asset.