Last year I added UV-C bulbs to my air conditioning system. One bulb is placed before my air filter and the second bulb is placed after my coils in space 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 one straight for an hour. But for someone like myself with regular seasonal allergies 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 HVAC maintenance and service appointments. I even have my ductwork professionally cleaned every two years. Despite all of these attempts at better indoor air quality, I was still noticing issues with shortness of breath, headaches, and occasional wheezing and sinus congestion. My HVAC technician recommended the UV-C bulbs at that point and I promptly scheduled an installation appointment for the following week. The first week 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 easily the best investment in my system yet, but after 8 months of use I started to notice a drop in performance. I had occasional headaches again and my lungs weren’t feeling as good 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 HVAC tech put in new bulbs last week and I have been living better again as a result.