We have plenty of deep box type air filters with pleated nylon filter medium. I understand that the direction of pleats need to be kept vertical while the box filter is fixed on to the frame. What is wrong if the pleats are in a horizontal direction? would someone clarify my doubt? is there any code / guide line for such fixing.

Do these deep box filter have a user manual?

gravity will cause stuff to accumulate on the upper surface/pleats reducing filter efficiency by 25%

This message has been edited. Last edited by: Jonesy,