OT: Can an Air Quality Sensor Detect Cats Using a Litterbox?

Random thought of the day...

I've often wanted to figure out a way to automatically turn on my laundry room vent fan when the cats use the litter box (it is in the laundry room, obviously).

Don't really want to mess with finely tuned motion sensors, or pressure sensors under the boxes.

So I picked up an air quality sensor (measures PM1, 2.5, 10), hooked it to an ESP8266, pumped the data to MQTT/Grafana and am going to trend it for a while and see if I can see correlation.

Might not work. Probably won't work. But it gave me something to do for a few minutes.

(side note - I can definitely detect when the dryer is running with it... lol... Litter box is TBD...)


You are too constrained in your thinking. What you need is a Litter Robot 3 Connect. Dominic Meglio (@dman2306) ported Nathan Spencer’s SmartThings integration, and it works well. The Litter Robot has a litter drawer into which all the poop and clumped pee is dumped, and it is sealed to keep all the odor in. The cats love it because their litter is always clean. You just have to change the litter bag every few days when it tells you it is full. It’s a real engineering marvel. It will change your life.


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What kind of litter do you use? What you may see with an air quality sensor is an increase in fine litter dust. Another option would be to do this with a VOC sensor (like a BME680) instead of an air quality sensor.

Cat urine has volatiles in there - like felinine and a few mercaptans. And heaven knows that cat poo has all sorts of volatiles - mercaptans and indoles. I know that a BME680 can pick up indoles. And I would be surprised if it didn't also pick up mercaptans.

Standard clumping litter. And it makes a reasonable amount of dust overall, so it "might" work... At least that was my thought. We'll see.

That was plan B. I have one sitting around here somewhere.... Probably should have just wired it up and did both at the same time.

EDIT: Nope, I was wrong. I have a CCS811... That is tVOC, not bVOC. Will just pickup a BME680, too.

Just heard from my Bosch rep today.

There is a BME688 coming out that can distinguish between three different gases. I don’t know if it’s available yet.


Ooh - the specs on that are excellent for my professional needs!


Picks up VOCs, VSCs and CO/H. Specific detection of VSCs would be superb. One of the bugs that I work with does this reaction:

C3H7NO2S -> C3H4O3 + NH3 + H2S

Having a sensitive/quantitative way to detect the H2S would save us a bunch of time.


Hmmm.. So a definite "maybe" on the air quality sensor and litter box. Needs days/weeks more data though to tell for sure.

Spikes were periods the cats were in there. And as expected, it is the PM10 that spikes the most.

My BME680 will be here Friday, so I'll get that setup in parallel this weekend.


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Well, PM for litter box detection isn't looking good. Sometimes it registers, but often does not. I'm sure if I put the sensor RIGHT next to the litterbox it may work, but the cats would destroy it in days or it would get so dust covered it may not read long.

I have a BME680 in place now, I'll see if that works any better in the location I have it mounted at... If not, it was a fun $15 diversion.

BME680, measuring kOHM resistance.



what about this one ? Detect Ammonia, could be nice too


OK, just to put a bow around this...

BME680 didn't work reliably enough. It would peak after litter box use, but it would also drift around a lot due to general environmental changes. So it was tough, but not impossible, to use for this purpose. Would probably have to do it on Rate of Change, not any fixed trigger value.

After moving the PMS5003 closer to the litter boxes, it seems to be the winner. Triggering the room exhaust fan @ PM10=25 has worked pretty reliably without false alarms. Maybe it misses some events, but every time I've checked, it ran. So I'm calling this done/success.


Just an update. Still working great!

I trigger the room vent fan on PM10 >= 20 to reduce 'false alarms'. It probably misses some events with the setting that high, but seems to work well enough.



I wonder if this could also be used for toilet going stinkers like all of us, turn the fan on whenever it smells nasty around the throne?

Don't think so, as this works due to the dust stirred up from the cat litter.

I did try to use two different VOC/TOC sensors first to see if that would work - it didn't seem to work reliably though.

Theoretically some form of Voc/toc/other gas monitoring should work for humans if sensitive enough.

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