Remove them from the wall to paint the wall.
Can you paint air return vents.
This is the best design decision.
Be sure to turn the vent cover over so you can paint both sides.
Give the spray paint can a good shake then use even strokes to apply the paint.
I would just clean them really well and then look for the spray paint that s meant for plastic to be sure it will really stick.
Once the return grilles are primed they will accept paint.
Do you have some vent covers who could need some updating.
Any time the vents are blocked or restricted in some way your furnace has to work that much harder to pull in the cool air from the room.
Paint will off gas and that does bother certain people and in reality isnt good for anyone.
Or have you ever spray painted your vent covers.
So you ll be fine.
If you are inside open windows before spraying and wear a paint mask to keep from inhaling paint particles and fumes.
I agree with painting them.
Condition the grilles with a special etching primer formulated with an acid base.
In most homes what seems to be typical is to paint the vent with a regular paint brush.
It will really make your vents look so clean and fresh instantly.
So in essence its no worse to paint the inside of that return as it is to paint the house.
Air return grilles are metallic a characteristic that leaves them less suited for paint than porous drywall.
The problem with this method is that the paint tends to ooze through the holes which leads to a partial blockage.
Spray the vent with a metal primer.
Probably will require 2 coats.
Spray the vent in a well ventilated area.
So if you are looking to do some simple upgrades clean off those vent covers and give them a coat of spray paint.
Brush paint the vents after they air dry when the paint has dried reinstall.
Painting your air vents to match your wall color makes them blend in with the wall leaving your furniture or artwork as the focal point of the room.
Let dry then add another coat or two until you ve achieved solid coverage.
This is a great upgrade project to do if you are planning on selling your home too to make it more appealing to buyers.
Finish the grilles using the appropriate application technique or the paint may sag.
However you can also purchase a decorative air vent that matches the design aesthetic of the room.
Carefully wash the vents and rough them with steel wool or a scotch brite so your paint will adhere.