This is something I just learned how to do properly. Here are a couple of videos to watch to show you how.
If the air coming out of your AC unit is smelling stale or musty it can make you sick. Recently I had a couple days of terrible headaches, low energy, and complete inability to do any work. I discovered I had not learned how to properly and completely clean my AC window unit, which we’d just begun using again.
If you have central air instead, look for any evidence of staining of a darker color around your vents or dark dusty stuff coming out of them. That is evidence of mold and/or mildew. This can make you sick. Have your vents cleaned.Better yet, get an EcoQuest air purifier and keep it running next to your air intake on an ozone setting that is tolerable for constant use. Once a week when gone for at least an hour, push the ‘sanitize’ button and turn your central air fan ‘on.’ It will run on high ozone setting for 1 hour, then return to its usual setting.
This company’s air purifier (Flair model, discontinued) saved me from chemical sensitivity in a new house and allowed me to recover my health.