I would normally remove them, so as not to cause them to be permanently "glued" to the wall. If this is done, it is very difficult to remove them, and the ducting itself, for cleaning. Also, i prefer to use a match color of oil enamel to paint them. The oil enamel is much easier to clean and does not literally catch the dirt, as does low sheen latex paints. If possible, I would spray them with a a close color spray can. Again, such a finish does not get dirty as quickly, is easier to clean and does not leave a high build of paint to restrict the air flow.

I don't believe in caulking them back on. I want to be able to remove them for cleaning.

In truth, from a pragmatic sense, it is best to leave them with the factory finish. Aesthetically, this might not always be pleasing.

Why does it matter if they are painted on the wall or off the wall? There is no standard for this, but they should do what the customer wants.

Paintguy,

You're right, ultimately, the customer should get what they want. My only point is that if painted on the wall, they tend to get "glued" to the wall and are difficult to get off for cleaning without damaging the coat of paint. Maybe it is just me, but over the years I have seen ducting really clogged with wall to wall dust and I have wanted to periodically remove them.

In terms of ease of long term maintenance, they are best left with the factory finish. That hard finish literally does not catch the dirt as badly and is easier to wipe clean.

It's very common to caulk the gap between wall and vent cover. A simple removal is a razor knife. Nothing more ugly than an ill fitted vent cover over a painted wall.

Since people don't repaint every week, making removal of a slim bead of caulk a major setback is unwarranted.

quote "it is best to leave them with the factory finish". I agree, but certainly paint and caulk them as needed