When you stop using your air conditioner for the year, you get to stop doing things like changing the filter every month (assuming the air conditioning system you have has a separate filter from your furnace). But what about when the weather is cooling down but has occasional spikes, so you use your air conditioner for only a couple of days each week? If that goes on for a month or two, do you still have to change your filter?

Pollen Still Exists

While your use of the system has clearly dropped, the amount of pollen in the air might not have. Pollen exists, even in fall (ask any ragweed- or cedar-allergy sufferer), and any time you turn on the air conditioner, those pollen grains will become trapped in the mesh of the filter. If you are still using the air conditioner by a fair amount, you'd likely have a pretty good buildup of pollen sitting on the filter, and you don't want that lying dormant in your home during the winter. Even if the use is no longer consistently every day, you should really change the filter one last time before mothballing the air conditioner for the cool-weather season.

If you've barely been using the air conditioner, however, say a couple of hours a week, then the question is whether you're allergic to any pollen types. If you're not, leaving the filter as is might not cause you a problem. You could change the filter at the beginning of warm-weather season if you wanted to be sure you started off with a completely clean filter. But if you are allergic, yes, get that filter out of there and put in a clean one.

Dust Still Gets Trapped

Another issue is that dust will still get trapped, too. If you're allergic to dust, you can follow the same protocol as someone who is allergic to pollen. But if you're not allergic, the situation changes slightly.

Significant use, again, would call for changing the filter when turning off the system for the last time before winter. There's no reason to leave a dirty filter sitting in the system. However, if there's been only minor use, you may want to leave that filter in and change the filter at the start of spring instead. This is because dust is going to float around your home and likely hit the filter anyway, albeit in much smaller, more random amounts. Look at any side table's legs in your home; even the vertical surfaces gather dust. That's happening to the filter, too.

In other words, any filter you put in now and then let sit is going to gather dust. If you turn on the system in spring with that filter, you'll already be starting out at a loss in terms of efficiency. If the filter is relatively empty already, you might consider leaving the filter alone, letting it catch that dust, and then changing it in spring, or even once over the winter and again in spring.

If you need help, call for air conditioning services.