Have you checked your filter lately? Every a/c unit should have a filter. Keeping a clean filter in your system is an important part of maintaining an efficient a/c unit. Its just as important as changing the oil in your car. All filters are measured on the particle size the filter can catch. There are 3 different filter ratings. I use MERV (Minimum Efficiency Reporting Value) rated filters. They give the a/c coils great protection and have good catching rates. With so many filter options it can get confusing. If you have any questions or need help selecting the best filter for your system please give us a call, we'll be more than happy to help!