Air return for gas furnace?

[William Horsey]

Question about the air return: Should duct work always be used to make-up the air return from the homes interior wall to the gas furnace? Can framed in drywall be used?

Thanks.

[Tom W.]

@William Horsey 

Mechanical code allows for the use of drywall cavities to move air as long as certain parameters are followed.

1) They cannot be used for supply air

2) They cannot be part of a fire resistance rated assembly

3) They cannot convey air from more than one floor level

4) They have to be isolated from adjacent concealed spaces by fireblocking

5) They cannot be used in exterior walls

In addition, there must be a direct, sealed connection to the furnace. No return can be drawn from the room in which the furnace is located.