But having those open windows means that it's not just air is getting in. There is:

Dust

Pollen

 

Allergens

And that's just the start!

Your filter will be working to clear all these those things out, and if your neighbors are putting on that room addition, you're going to get their construction dust as well. All of this makes September a great month to change your filter!

Do what I do, order a filter from filter-guru.com (or a few) and wait until a Saturday morning. Say "I'm going to change out the filter and then watch the game." Give yourself a couple of minutes then open the windows and watch the first game of a college football Saturday.

You're on your own to figure out what you do after that to watch the second game.