cats

Use unscented, clumping, cat litter. Good unscented cat litter doesn't really smell like much of anything.

Run your bathroom fan, it will suck clean air from your house into the bathroom and flush it out so that even as you approach the bathroom youl be smelling air from the rest of the house and bad odours won't build up.

Scoop the soiled, clumped litter into a green bin, and then tie the bag closed between scoopings.

Avoid "light weight" litter, that just means it's lots of fine particles that are more likely to fly around.

Dis you try wood pellets?

This definitely isn't the best solution, but when I got one of those litter robots that automatically dump into a sealed compartment, I haven't noticed the litter smell.

I use plain Arm & Hammer clumping clay litter.

We use a "flushable" clumping corn-based litter. We don't actually flush the clumps of litter, that's a recipe for disaster. But it does mean I can scoop poops directly into the toilet and flush them. (My cat never got the memo on burying poops, but she does warn us when she's going to go, so I can get them right away.) I scoop the clumps into those little green dogpoop bags, and put those in a lidded can with a liner. It's not perfect but it's not bad. We also discovered our bathroom vent fan just went into the walls, so we had a contractor run a proper vent duct to the outside, made showering in there much better as well.

It doesn't eliminate the smell, but air purifiers can reduce it significantly. We have a decent one in the room where the litters are that turns on on a schedule. It's a bit annoying that if the cats use the litter just when it's turning off then it's kinda no use.

My long term plan if I ever get around to it is to build a cupboard type thing to put their litter in with an extractor fan to the outside.

Litter robots could help, but all the people I know who have them said they just replace some issues and chores with other issues and chores in the end.

Honestly, look into the Breeze litter boxes. They're not automatic or anything crazy expensive, but it really does make a HUGE difference. I've been told by multiple strangers "I thought you had a cat?" after being in my house a while because she hides and the box generally cannot be smelled. If you change the pads regularly (i.e. before they are full), replace the pellets 2-3 times a year, and clean the box itself when replacing the pellets, the only smell you will have is from poop. I personally buy the bioplastic dog poop bags in bulk, and just use those to quickly grab and dispose of it.

When we used regular litter the cats tracked it everywhere, flung it out of the box, and it always had a smell, even when cleaned daily. I have none of those things with the Breeze boxes. We were using two when we had 3 cats and I had to replace the pads every 3 days. Now with one cat I replace the pads every week to two weeks depending on whether she divides her usage or fixates on one. We pick up the poop as soon as we notice it, which is usually very quickly because they can't really bury it as well. I will never go back to traditional litter.

My neighbor uses crushed walnut shell litter and I can never smell anything. I was thinking of getting it too.

When I still had kitties (and a house), I bought a litter box with a lid. I then fashioned a vent hose with a 120mm 12V PCM fan running at low RPM. The hose went through the ceiling in a closet and exhausted out an attic vent. Zero cat box smell and no noise. While my exact implementation isn't available to everyone (like in apartments), the basics can be adapted to almost any situation.

The quicker the poo dries out, the quicker it stops smelling. This is one of the benefits of crystals, but I prefer wood pellets for the same reason.

There are for sure brands that are more perfumed than others, and there are some that are unscented. Of course, the scent is there too mask the pee smell. We use scoop away, which is scented, but not heavily so.

We have a covered litterbox with a little charcoal filter in the lid, and that helps some. Also, since we have dogs who like to look for cat poo roca, we have ours in a closet with the sliding door open just enough for the cat, and that helps too.

We use a pure-clay, non-clumping litter for that reason. I hate the chemical smell of the clumping litters. I’ve also heard really great things about wood pellets.

If you clean the litter tray regularly, replace the litter once per week, and keep the house well ventilated then there should not be a bad smell. If there is it may be worth taking your cat to the vet if their poo smells worse than usual.

For a spray that actually will kill the odor, try Ozium. But that probably needs to be an additional tool in your arsenal.

We use swheat scoop and it is pretty neutral and if you clean it regularly, doesn’t smell much

Put the litter box in the garage with a cat door if that's an option.

I assume you're referring to the clay litter? You probably just want an air purifier. You will have litter smell and dust for a short time is all. The one problem, is that the fine clay dust will make mincemeat out of most purifiers. You'll want a good one with easily replaceable filters or easy to clean filters. If they're replaceable, cost is also a factor. Or, you can get two furnace filters and rubber band it onto either side of a box fan and use a smart plug to run it now and then.

Using litter tray liners virtually eliminates the smell in my apartment. Also recycled paper litter. Of course, now my overlord the cat asks me to give him a fresh one multiple times a day, since he loves the freshness too.

Get yourself one of these bad boys:

https://www.citikitty.com/

Try fresh step crystals. It lasts a month and doesn't smell. I've had up to 9 cats before, I tried so many solutions. Scoop the poop every couple of days, no problem