I have been really loving these HEPA air filters that I bought. I had never before tried HEPA air filters and I now think that they are the best type of air filters around! These are for my central heating and air conditioning system unit. Though I know that HEPA air filters are also available for portable air conditioning systems, portable air purification systems, whole home air purification systems and even vacuums believe it or not! HEPA really has the world of air filters locked down I would say. And with good reason. Because these HEPA air filters are totally great and I would never go back to the old air filters that I used to buy for my central heating and air conditioning system. I was always wondering why the air quality in my home sometimes would get bad. It was all because of the air filters! Now, with these HEPA air filters I should not have to deal with any such thing any longer. HEPA air filters as long as you change them when they are dirty will provide the best possible air quality to come out of your central heating and air conditioning system unit. That is the truth! I did not believe it when a friend told me about HEPA air filters being this way. And that is also why I decided to give them a try. I am so glad I did! Because now I will never turn back and keep on using HEPA air filters when I need to have some kind of filter in my central heating and air conditioning system.