Smallest particulate matter air quality sensor for ultra-compact IoT devices
28 comments
·July 27, 2025zevon
f1shy
Lying?
TimByte
My guess is they're relying on natural air convection and using a more sensitive optical setup to compensate for the lack of forced airflow
f1shy
They don’t give lots of heat, so convection is negligible.
trailbits
Also wonder how the sensor can stay clean without a fan. I suppose mounting upside down would help. Other fanless designs require periodic cleaning.
dist-epoch
The integration picture shows an "optical cover" transparent surface. I guess it's not meant to be used in highly contaminated areas.
dist-epoch
They have some tech specs: https://www.bosch-sensortec.com/media/boschsensortec/downloa...
> Laser light is emitted from the sensor and focused by the sensor lens at approximately 5 mm from the top of the sensor’s lens surface.
> Particles traveling in free space due to the natural ambient airflow are detected when passing through the laser focal (sensitive) region.
> Due to the interaction between particles and light, the light scatters in different directions; a fraction is back-scattered towards the sensor, where the integrated photo-detectors detect it.
> The back-scattered signal is processed by unique algorithms (based on particle counts, particle relative velocity, probed air volume during measurement) to derive the particulate matter mass concentration.
trailbits
That's pretty much how all laser particle counters work... except the good ones use a fan and a chamber. Guess we'll have to wait and see how this compares to the reference sensors.
ImaCake
Yep, I suspect this is all marketing fluff and no substance. I see a lot of superlatives but no substantial technical breakthrough here.
9dev
Waiting for Achim Haug of AirGradient! What’s your thoughts on this?
ahaucnx
Hahah. Thanks for calling me!
We actually have a sample of the Bosch in our office but haven’t come along to test it yet. Maybe with this call, I will get our team onto it.
The form factor has pros and cons in my opinion. The size and lower energy consumption definitely opens new applications but the problem is that it needs a clear field of view to do the measurements.
This could in turn restrict the applicability, eg as a wearable sensor.
In general I think it’s great to see innovations in the PM sensor field but often minimizations go on costs of accuracy.
We saw that for example with the Sensirion photo acoustic CO2 SCD4x sensor that is tiny but needs more black box algorithms to compensate for certain environmental conditions that then limits the range of applications.
pppone
I've been running multiple Sensirion SPS30 PM sensors for years, and I'm honestly amazed how well they've held up. Particularly with respect to, within their spec'd error, how new/unused SPS30s report similar values to my heavily used ones.
Curious if there are any maintenance requirements for the bosch sensor.
TimByte
The fact that it's fanless and still works reliably makes me curious how well it handles airflow variability in real-world settings though
Catbert59
Many particle sensors are useless in foggy/hazy conditions, which ruins many citizen science projects in terms of data quality. Currently, the best solution is to calculate the dew point and then switching them off once you hit a specified limit.
How does this model deal with this?
pppone
I don't think it would. Data in these instances would have to be ignored.
You can detrend for high humidities, but once water condenses, the only way round this would be to add a drying instrument.
HPsquared
I wonder if a radiant heat source beside the sensor, maybe also somehow focused in the same area, could get rid of the condensed water.
Catbert59
The problem is not condensed water. This can be solved with heating.
It's that fog is being detected as a particle. This distorts the measured values.
TimByte
I didn't see anything in the article about humidity compensation
smingo
The entire device is tiny: 20mm x 5mm x 5mm approx. It looks to work using a small laser and a lens which focuses the beam about 5mm above the device. The sensor unit contains a photodiode(s), and algorithms count the particulates. It looks to need a heat sink.
alliao
love this... while the politicians busy angle themselves over stances on whether air filtration is required for public space during a pandemic engineers and companies come up with products and solutions ready to deploy.. it is my dream that our last generation gave us clean-ish water, and we can somehow pass down clean-ish air...
progbits
I mean this is cool but the size claims are somewhat misleading. They only sell you a sensor element on flatflex PCB, then you need to add own metal cage for thermal dissipation and a lens, so the overall size is significantly larger.
This is great for flexibility but very impractical especially for DIY space. Hopefully small fully integrated modules on something like edgeconnector PCB come out soon enough.
joshvm
Unless I misread, the lens is integrated, but Bosch recommends an optical window to protect the device. The integration guide is pretty comprehensive. Many fan-based air sensors require some specific enclosure considerations to separate the in/outflow.
Sparkfun sell a module with a ground plane + thermal pad as heat sink. This is suggested as OK by Bosch, though adding a small heatsink is probably a good idea, or just mount the enclosure on a metal surface.
https://www.sparkfun.com/sparkfun-air-quality-pm1-pm2-5-pm10...
https://www.bosch-sensortec.com/media/boschsensortec/downloa...
arnejenssen
Cool. So we could get air quality apps for the phone or smartwatch?
mjs
Might need to wait a few generations. It costs ~30€ for a single unit (maybe half that at volume?). And not waterproof.
progbits
It needs an external lens anyway so you could shove it into the camera assembly, waterproofing is not an issue.
Cost is one, but this isn't something you can measure quickly on demand, you want to keep averaging multiple measurements over time. So unless you want to hold out your phone for minutes to get a measurement it doesn't seem practical.
SideburnsOfDoom
FYI, it is a "Smallest sensor, for particulate matter", not "sensor, of Smallest particulate matter"
Does anybody know how they actually do it without a fan and a defined volume around it? The marketing fluff says "It applies sophisticated algorithms to measure the PM2.5 concentration directly in free space, without requiring a fan", so I assume the main difference to traditional PM sensors is the software?