Pure characters equal= 99% successes, not hurt others= save and protect oneselves, always keep vigilant eyes and mind, away from trouble environment, good win, bad lose no matter whenever and wherever!
The HVAC system in the US apartment is usually one unit per apartment. The return air is within the the individual apartment, not circulation throughout the building. Also, people don't usually open windows for fresh air often here. My parents complained about the "stuffy" air in my house when they were here visiting. All that makes the indoor air poisoning possible.
This is a really sad case. In 2002, I lived in a $700 per month one bedroom apt in a nice community in plano, tx(North of dallas). I always walked with light weight slippers. But the lady downstairs, often use broom to make noise to ceiling…complaining…one night, she called the police. Glad two friends came visit me, I told the police, “Sir: I am not playing loud music or anything, just normal cooking and walking.”…Then, 4 mos later, due to job change…I moved away from that apartment. This lady is crazy.
Renting an apartment in US often encounters this kind of issue. I remember in 1997, I lived in a 2nd floor nice apartment in Baltimore, the downstairs renters were american medical school student/ resident couple. He knocked our door one day, complained about us making noise so he couldn’t sleep! Me and my husband just did normal living! I guess as a top school (Johns Hopkins University) medical student, he was under a lot pressure. We only stayed in that nice apartment for a year then moved to other city, so don’t know what happened to them afterwards. Wish him the best! The wife was nice, I met her in the laundry room once, we had a friendly talk briefly, she didn’t mention the “noise” issue at all😀