Fresh air is brought in from an outside intake hood and dispensed in the return air duct.
Fresh air intake into furnace room.
There s also a separate fresh air intake which is currently covered with dry wall.
There are often two separate vents that go to the outside for a forced air furnace.
The purpose of it is with the new homes and energy efficiency of the homes they are sealed so tight that it allows no fresh air to come into the furnace room area to allow fresh air to flow into.
Some modern furnaces actually draw air from outside directly into the unit.
The air passes through the filter of the unit and quickly passes over the supercooled coils inside.
The gap is big enough to allow a lot of air to get in i ve never seen a open fresh air intake for combustion air in newer houses.
This reduces the amount of cold dry air that is pulled into the home.
So when you remove the filter from a return plenum in a gas furnace installation in a new home and look closely you ll likely note some kind of system that allows fresh air to be drawn directly from the outside and delivered into the return of the furnace cabinet.
It is then heated by the furnace and distributed through the home.
One brings air into the furnace room and dumps it on the floor.
If you re simply concerned about the quality of the air entering the home it s possible that you could install a filter on the intake.
Unfortunately the fresh air intake you have described is the second type and does not provide direct combustion air to the furnace room as it is directly connected to the return air plenum for.
This return air intake grille typically includes some type of filter to keep dust and debris out while allowing air to pass through.
Also with the increasing concern of radon infiltration fresh air becomes an even greater need.
The indoor portion of your unit has an air conditioner return air intake usually located on the ceiling.
Many people erroneously close this one off because it freezes out the basement.
In many homes the fresh air intake is simply an open duct ran from an outside vent into a basement or any room housing the home s furnace.
Fresh air intakes can be in multiple locations throughout your home especially in newer homes built to modern building codes requiring homes to be much tighter than older homes.
With today s homes being built increasingly airtight it is becoming essential to bring fresh air into the home mechanically.
In these cases an air intake will also be used.