My sister has really bad allergies and sinus problems. One year I had to throw out all of my perfumes because they were irritating her even though they were in my bedroom. When she moved into an apartment during her third year of college, it was a big deal because the only apartment she could find had window air conditioner units. It’s not that she is bougie and won’t accept anything less than an HVAC, but rather window A/C units don’t have great air filters. Central HVACs have air filters that are bigger and more innately designed to filter out particulate matter. The air filters for window air conditioners are basically sponges and don’t do a good job at filtering out much from the outdoors. My parents were so concerned about what this would do to her sinuses, so they purchased air purifiers for every room in the apartment. They even put air purifiers in her roommate’s room to make sure the entire place was filtered. Even though they don’t work super efficiently, it’s important for her to regularly swap out the air filters in the window a/c units so that they don’t clog up. A clogged a/c unit can cause it to overwork and lead to a blow out. Her new apartment has been great other than that, and she really enjoys her roommate. They have been living together for over a year now and they seem to really get along. I love when I go to visit because I think her roommate is cool and I think she has a crush on me.