Greetings!

I am replacing old wooden wall paneling with drywall.

One of my furnace air return vents is on a wall I am drywalling. The sheetmetal return ducting is flush with the framing, not extended out – when I drywall around it, the metal ducting will be 1/2 inch removed from the grill/register.

My question: what should I do to avoid dust from the cut edges of drywall getting sucked in to system? i.e. all the air coming into this return first passes the cut edge.

Few ideas:
1. extend the ducting 1/2 inch out from the framing so it is flush with the drywall paper face
2. use drywall primer on the cut edge to encapsulate the edge dust
3. use some sort of tape over the cut edge for encapsulation
4. not worry about it / change the furnace filter more frequently

Any thoughts are appreciated!
Matt