Last year I added UV-C bulbs to my a/c. One bulb is located before my air filter and the hour bulb is located after my coils in area leading to the opening to the entire duct system for the house. The bulbs utilize a special ultraviolet light frequency that is so bright that it kills essentially anything that it comes in contact with at close enough proximity. They’re so bright you’d go blind if you stared at 1 straight for an hour. But for someone like myself with regular seasonal pollen irritations and bad enough asthma as it is, they’re amazing. I use the highest allergen rated air filter that my hardware store carries and I am thorough and frequent with my Heating and Air Conditioning service and service appointments. I even have my ductwork professionally cleaned every numerous years. Despite all of these attempts at better indoor air conditions, I was still noticing concerns with shortness of breath, headaches, and occasional wheezing and sinus congestion. My Heating and Air Conditioning serviceman recommended the UV-C bulbs at that point and I promptly busy an installation appointment for the following week. The first month with the bulbs was like a dream, no headaches of any kind and I felt like I could breathe easier with little to no nasal or sinus congestion. They have been unquestionably the best investment in my system yet, however after 8 weeks of use I started to notice a drop in performance. I had occasional headaches again and my lungs weren’t feeling as superb as usual. I assumed that the bulbs would burn out completely when they had expelled all of the ozone gas inside, but I was wrong. You could have those bulbs in their creating light for years after they have been used up completely for their antimicrobial properties. My Heating and Air Conditioning tech put in new bulbs Last weekend I have been living better again as a result.