Hi I wanted to know if a Return Air Filter Grille would replace me having to put an air filter in my air handler. I have a return underneath my air handler which is easier to access than swapping out the air filter under my air handler.

Please advise, thanks.

Yes you can use them but the total area of the replacement unit must equal the area of the original filter. You can also get smaller units that fit in the wall and replace each room return.

YouYou should still replace your filters on a regular basis to protect your air handler operating efficiency.

As was previouly mentioned. Plus its far easier and cheaper to replace ONE filter than it is a dozen or more (taking a wild guess)