Below is my furnace and I need to change the filter however I am unsure which way is the airflow direction. Red or Blue?

enter image description here

  • 2
    Remember that the air needs to be filtered BEFORE it enters the air handler and furnace.
    – longneck
    Mar 11, 2014 at 12:51

1 Answer 1


Red, here's a diagram that shows airflow in a furnace: enter image description here

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