My husband has been having a lot of difficulties with his allergies lately. I had read that by simply installing a HEPA air filter into your furnace or air conditioning unit, you could remove a lot of allergens from your air. I went to the home center and asked if they carried HEPA air filters for my air conditioning unit? As soon as I got the HEPA air filter home, I put it in the air conditioning unit. I couldn’t believe the HEPA air filter wouldn’t fit. I called the HVAC company to see if I needed a specialty sized HEPA air filter for my air conditioning unit. They asked me for the serial number of my AC unit? The HVAC tech told me that my air conditioning unit was not made to accept a HEPA air filter. I had to have some customizing done to my AC unit before I could use a HEPA. I had no idea what he was talking about. He explained that if I were to put a HEPA into my AC unit, I would need to have a bigger and heavier fan. Without a bigger fan, I wouldn’t be able to get enough airflow, and my air conditioning unit could end up being damaged beyond repair. This I understood. He told me they made portable air purifiers, which could be used in whatever room my husband was in. If the portable air purifier worked, I could always have revisions made to the AC unit, and then I could use the HEPA, but it was going to be expensive.