That is the only thing that is passing between the two units.
Furnace outside air intake.
There is no chimney in the house gases are vented through pvc pipe out the walls seperate 2 for water heater and furnace has 2 4 pvc plus this 6 outside air intake.
Through mechanical ventilation devices such as bathroom or kitchen fans that vent to the outdoors or heating ventilation and air.
You don t want to bring any of those exhaust gases back into the home heating system.
But during a wildfire they can pour unhealthy air into your home s interiors.
If airflow comes in from the top it is a downdraft or downflow furnace.
Keep the intake hood away from exhaust vents dryer vents and furnace vents.
Outdoor air including fine particles from wildfire smoke can enter your home in a few ways.
However this does not mean that your home does not need a fresh air intake just because you have a high efficiency furnace.
It is much more efficient to use outside air for combustion air.
That air is replaced by cold outside air that will then need to be heated.
Baseball is like church.
If your furnace draws combustion air from inside the house you are using air that you have already heated.
The air that is surrounding your outside unit is just outside air and the air coming from your inside unit is inside air.
If return air comes in at the bottom it is an updraft or upflow furnace.
How your ac unit works.
Since high efficiency furnaces draw air directly from outside the furnace itself does not require a fresh air intake in order to replace inside air that otherwise would have been drawn from the room the furnace is located in.
There are alot of gas furnaces in this neck of the woods that have no outside air intake granted these are mainly older homes.
The indoor portion of your unit has an air conditioner return air intake usually located on the ceiling.
Through open windows and doors which is known as natural ventilation.
Locate a spot for the fresh air intake hood on the outside of the home.
Ways that outdoor air can enter a home.
Many attend but few understand.
To keep smoky air outside close the intake using the damper.