I had to buy a current air filter for my cooling system, however there were so many of them at the store that I got a little bit confused, but replacing your air filter in your a/c or your gas furnace on a proper basis is the best way to keep your Heating & A/C system running for a very long time. Having clean air filters can also help you to keep your heating & cooling bills lower than they would be otherwise; A lot of people, adore me, tend to forget about decreasing their air filters for months & months at a time. I have a rough time remembering to change mine, however most Heating & A/C companies recommend that you change cheaper air filters every thirty days or so. If you Springtime for higher end filters, then you might be able to let them go for nearly several months at a time. When I called to get my Heating & A/C serviceman’s opinion, she said that a wonderful rule of thumb would be to change your air filters every ninety days. Since I have a animal & a pet & they both shed, I figured that I should definitely change my air filters even more often than that. When I got to the local hardware store, there were so many air filters in the heating & cooling aisle that I got all confused. I started studying about the pros of HEPA filters & I ended up purchasing one of those to put in my a/c. Now that the air filter is in & working, my indoor air pollen levels is much better.