The air filters smell awful

It is the annual change of your filters a day. I change my filters once every 3 months because I like to stay up on that maintenance. I have a pile of brand new ones which I opened and placed in a stack on my basement floor. It’s probably about 2 years worth. I open them because when I do the change, I really don’t want to spend time opening them and in this way I can quickly do the change. I used to have an HVAC technician come to my house and do this but he gave me a lesson on how to do this myself so I can save money. I always loved that about the HVAC company around here, they always went above and beyond to look out for their customers. The last few days everything in my house started to smell very awful. I didn’t know where it was coming from but then thought maybe something died and maybe it was in my heating vents. I had to call the HVAC company and they sent out a heating and cooling tech. After he examined it, he said the smell was cat pee. I was confused at first but my cat Max wouldn’t have done that, would he? I checked the pile of air filters on the basement floor and they all smelled. It was disgusting and I was disgusted with Max. The HVAC technician replaced the air filters I had and said I probably should store them somewhere else going forward. I learned an important lesson that day, don’t leave your air filters on the ground, you never know if your cat will pee on them.
electric heating system