When an air purifier is running but a room still feels stale, do not assume the machine needs replacing. First separate three causes: a continuing odor or particle source, a ventilation problem, or filtration that is undersized, overdue for a filter change, or operating in the wrong room.
Air purifier room still stale: quick answer
Start with the source: cooking, smoke, moisture, pets, cleaning products, or another ongoing contributor can keep changing the air faster than one purifier can clean it. Then check whether outdoor air is suitable to bring in, and whether the purifier’s filter, placement, and room size match the space where people actually spend time.