When i started my job just after covid, I found out that my coworkers hated the ~5 air purifiers that were bought for the few staff that were in every day, because they were incredibly noisy. They celebrated the day they were allowed to stop turning them on.

I asked if they ever changed the filters, to which they replied 'you can do that??'

...The filters didn't need changing, because all 5 of them still had plastic on them, and now we use them to circulate air if a room gets stuffy but another room is too cold (our HVAC is poorly adjusted for the building). They do that quite well, and very quietly too.