The Smell Problem in a Small Flat

Living space per person in Hong Kong is given as roughly 172 square feet in a government press release citing the 2021 census; a separate compilation of the same 2021 data puts it at about 161. Both claim to rest on the same census, and the gap probably comes down to how the figure was defined or rounded — we list both rather than picking whichever sounds better. Broken down by housing type, public rental housing runs to about 150 square feet per person, and subdivided flats go as low as about 48.

For a litter box those numbers are not abstract statistics. They are the volume of air available. In a 500-square-foot house the smell has plenty of space to dilute into. In a 150-square-foot public housing flat holding a family of three, or something smaller, it has nowhere to go — the same quantity of cat urine simply sits at a higher concentration. That is physics, not a question of which brand of litter works hardest.

“The whole flat smells of it” is the common complaint in a small home. On placement, most small flats offer the corridor, the bathroom doorway, or under a bedside table, and not much else. The principle is simple: away from the food and water, away from where you sit, and ventilated as far as possible. But “ventilated as far as possible” is often not achievable here — plenty of rooms have a single window, and partitioned rooms and subdivided flats may have only a high window or none at all. Relying on opening a window to clear the air is not realistic in a lot of homes, and that limit is worth stating honestly.

A covered box looks attractive in that situation: sealed, tidy to look at, no smell escaping immediately. But there is a trade-off to think through — sealing it concentrates the smell inside the box, and the cat takes that concentration every time she goes in. Some cats will refuse, and will go beside the box instead. A covered box suits the owner; it does not automatically suit the cat. Choosing one is not only about whether you can see in from outside, it is about whether she will walk in.

In a small flat, size should not be the last line of small print on a product page. It should be the first filter. Buying one and then finding it will not fit the corridor, or that it fits but she cannot turn around inside it, are both things you discover after the money is spent. Measure the space first, then look at capacity and odour control. Getting that order the right way round matters more here than almost anywhere.

Beyond the box itself, the litter you choose and how often you clean it both get amplified by the weather here. The Observatory’s 1991–2020 normals put average relative humidity at about 78% across the year, holding at or above that from March to September. Damp can make some clumping litters start clumping before they are used, and go hard if stored for a while, which makes them clump worse when it counts. That last point is mainly the consistent line from the trade and retailers; we have not found independent test data for it, though it is consistent with the humidity figures we did verify. Whichever litter you use, in a small flat the cleaning frequency has to keep up with how heavily the box is used, rather than following a rhythm that worked in a larger home.

Worth knowing: if she suddenly stops using her usual box, strains without producing urine, or cries inside the box, those are not a smell problem in your home. Those are signs to get her seen immediately.

This article is general background, not veterinary advice. If your cat shows anything that looks like a health problem, ask your vet rather than deciding from an article online.