Short answer: yes, they still smell sometimes. Anyone who tells you otherwise is either selling you something or has only owned one cat.
But here’s the part that matters: they smell significantly less than a manual box that’s been waiting for its once-a-day scoop. I noticed the difference within 48 hours of setting up the Litter-Robot 4. Miso used it, the box cycled seven minutes later, and by the time I walked past the bathroom the smell was already gone. That had never happened with a manual box — no matter how good the litter was.
So let’s talk about where the smell actually comes from, because the answer changes what you do about it.
Why Automatic Litter Boxes Still Smell (Sometimes)
The core logic is sound: remove waste quickly, reduce odor. But there are a few places it breaks down in practice.
The waste drawer. This is the main culprit. Once waste gets sifted into the drawer, it sits there until you empty it. If you’re going 7–10 days between empties — which some manufacturers imply is normal — you’ve got a week’s worth of waste in a small enclosed space. Open that drawer and, yeah. Even the Litter-Robot 4’s well-sealed drawer starts showing its limits around day 6 or 7. I empty mine every 4–5 days and it stays manageable. Wait longer and the smell migrates through the plastic.
Urine residue. Solid waste gets sifted cleanly, but cats that consistently use one corner of the globe can saturate that spot. Over time, even with clumping litter, fine particles and residue build up on the globe walls. I do a wipe-down with an unscented cleaner every three weeks or so, and that keeps it in check.
The litter itself. This one’s underrated. I’ve run the same box with cheap supermarket litter and with Dr. Elsey’s Ultra, and the difference in ambient smell is bigger than the difference between box models. Your litter choice matters more than most people give it credit for.
Which Boxes Handle Odor Best?
Litter-Robot 4
Whisker added the OdorTrap system specifically to address smell complaints from the 3 Connect — a tight-sealing waste drawer, carbon filter, and a carbon pocket in the globe. In my experience with one and two cats, the room smell between empties is minimal for the first five days. Day six and seven you start to notice it. Empty before you think you need to and you’ll stay ahead of it.
Leo’s Loo Too
The active deodorizer spray is the differentiator here. After each cycle, the box sprays a deodorizing agent into the globe — you can set the frequency in the app. It works. In my small bathroom I could genuinely tell the difference versus running it without the spray. The cartridge costs about $12–$15/month, which adds up over a year, and if you have a sensitive cat you’ll want to watch how they respond to it. But for odor control day-to-day it gives the Leo’s Loo Too a slight edge.
PetSafe ScoopFree
Crystal litter is a genuine odor weapon. It absorbs and neutralizes urine rather than just clumping around it, which means the smell stays controlled even in an open-top box. I was skeptical about this — no lid, less smell seemed counterintuitive — but in testing it held up better than I expected in a smaller room. The disposable trays mean there’s no long-term buildup; when the tray’s done, you toss it.
Budget Auto Boxes
The cheaper boxes (sub-$200) still beat a neglected manual box on smell, because they’re removing waste faster. But don’t expect much beyond that. Small waste drawers, no odor-specific features, thin plastic that lets smell through quickly. They do the job, just not as well.
What Actually Reduces Smell: The Practical Stuff
Get better litter. Seriously. This is the highest-impact change most people aren’t making. Dr. Elsey’s Ultra, Fresh Step Crystals, World’s Best Cat Litter — any of these outperform generic supermarket clay by a meaningful margin. The extra $5–$8 per bag is worth every penny.
Empty the waste drawer more often than you think you should. The 7–10 day figure is marketing. With one average cat, 5 days is where I’d draw the line. Two cats: every 3 days. Multi-cat homes: daily check, empty when it’s more than half full. Takes 90 seconds.
Do a full litter change every 3–4 weeks. Auto boxes make people lazy about this because they’re not scooping manually, but fine waste particles and urine residue accumulate in the litter over time even when clumps are being removed. I set a phone reminder. Without it I’d definitely forget.
Ventilation helps more than people realize. I moved the box from an interior closet to the bathroom with a window cracked, and the ambient smell dropped noticeably — not because the box changed, but because the air moves. If you’re fighting persistent smell and everything else is in order, look at where the box is sitting.
The Honest Answer
Automatic litter boxes reduce smell noticeably. They don’t eliminate it — and anyone promising otherwise is overselling. The best ones, set up right with good litter and a realistic emptying schedule, keep a one-to-two cat home genuinely fresh between maintenance sessions. That’s a real improvement over a manually-scooped box for most people.
But the biggest real-world upgrade most people experience isn’t from the box’s odor features — it’s from the consistency. When the box cleans itself seven minutes after each use instead of waiting for the once-daily scoop, the waste spends so much less time sitting out that the smell problem mostly solves itself. That’s what changed things in my apartment. Not the carbon filters. The timing.
Good litter, frequent drawer empties, regular full changes. Get those three right and whatever auto box you pick will do the rest.