Are air purifiers a waste of money if you already vacuum twice a week? Purifiers

I bought a cheap laser particle counter before the purifier, which is the only reason I can say anything useful. Evening baseline in the living room was 8,000 to 12,000 particles per cubic foot at 0.5 micron; with a mid-size HEPA unit on speed two it settled to roughly 1,000 to 1,500 within forty minutes and stayed there while it ran. What did not move at all was the dust on the shelf, because that is mostly heavier fibre that falls out of the air in minutes and a purifier never gets a chance to see it. The smell only changed on the unit with an actual carbon brick in it, not the thin carbon-dusted pre-filter that most of them ship with.

I own three and regret two. The one I would buy again is a plain box with a big filter and a dumb dial. The two regrets were both app-controlled with a sealed proprietary cartridge, and the replacements are close to a third of the purchase price every year, which nobody puts on the box. Before you spend GBP 250, price two years of filters for whatever you are looking at and then decide.

Slightly disagreeing with the top answer, only on emphasis. With cats the thing you are actually chasing is the allergen carried on skin flakes, and a decent chunk of that does stay airborne for hours in a carpeted room. My wife's eyes stopped being red in the evenings about ten days after we started running one in the room the cats sleep in, and that was the only change we made. It did nothing for the visible dust, exactly as described above.

Windows first. Sealing draughts is cheap, permanent and does not have a running cost. Then if you still want one, buy on clean air delivery rate for your room area rather than on the claimed square footage, which is always quoted at the top fan speed nobody can stand to sleep next to.

Not a waste, but the value is mostly invisible and that makes it hard to feel good about. If you want a cheap test before spending GBP 250, tape a MERV 13 furnace filter to a box fan for a weekend and see if anyone in the house notices anything. Published chamber testing puts that crude single-filter version around 111 CFM of clean air delivery, which is genuinely low but not zero, and it costs about the price of a takeaway.

Litter smell is not a filtration problem, it is a litter problem. Bigger box, more of it, scooped twice a day, and a carbon layer as the last resort. I ran a purifier next to a covered box for a year thinking it was helping and the actual fix was switching to an uncovered tray so the smell stopped concentrating and then blooming every time the cat used it.