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Air quality monitors: paying more does not get you more accuracy

airgradient.com

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Re: Air quality monitors: paying more does not get you more accuracy

#61

Post by ioulian »

For people who use Home Assistant, I've gone with DIY route with ESPHome [1] and senseair CO2 sensor. You can buy those sensors for +- 26 USD on AliExpress. Together with 5 USD, ESP32 devkit, it's mostly "solder"-n-play.

Of course, I only have one of them, so I can't say if they are accurate, but I just need to know if the CO2 levels are normal (+- 400ppm) or high (+1000ppm), to open a window. I have tested it with just blowing on it, the CO2 value jumps up, putting it near a window, goes directly to +- 400.

I haven't had any strange readings with it, ESPHome developers really made an excellent product, that is stable and "just works". You can even calibrate the sensor by putting the it outside (but I haven't really bothered with it).

ESPHome has also support for a lot of other sensors that you combine on a single ESP32 module.

[1] https://esphome.io/components/sensor/senseair.html

Re: Air quality monitors: paying more does not get you more accuracy

#62

Post by Leo_Germond »

vbezhenar wrote: post #51

I recently bought one air quality monitor (levenghuk wezzer something). Generally it works, but after few dozens of minutes its temperature sensor starts to display like +5 degrees compared to proper temperature. Very weird.

Membrane sensors have to get very high in temp locally in order to do a membrane cleanup, thos being large compared to a temp probe, the probe is probably catching of the heat because it is not properly isolated. Some SW model for heat flux can somewhat reduce this effect but in general this is AFAIK an open problem for miniaturized AQ sensors.

Re: Air quality monitors: paying more does not get you more accuracy

#63

Post by Wolfenstein98k »

vbezhenar wrote: post #51

I recently bought one air quality monitor (levenghuk wezzer something). Generally it works, but after few dozens of minutes its temperature sensor starts to display like +5 degrees compared to proper temperature. Very weird.

I think it's because the unit heats up over time, and its sensor can't adequately adjust for that.

My baby monitor does the same thing - the temperature tracks up after a half hour or so. The unit is warm to the touch by that point.

Re: Air quality monitors: paying more does not get you more accuracy

#64

Post by agos »

athollywood wrote: post #9

I bought a fairly expensive air quality monitor. Accuracy wasn’t what caused me to go with a more expensive model. I wanted CO2 readings, which most models under $200 don’t provide.

can you share which one was it? I'm also looking for one, and CO2 is surprisingly uncommon. I'd also love for it to be HomeKit compatible, which makes it nearly impossible

Re: Air quality monitors: paying more does not get you more accuracy

#65

Post by 2rsf »

amatecha wrote: post #23

My three AirGradient DIY units are going strong. They seem very accurate -- strongly correlating with nearby weather stations and online services. Definitely nice to have high-granularity/accuracy details both indoors and outdoors. It's also really interesting to see different "trends" and how different weather conditions correlate with (and/or affect) air quality!

Are there online co2 measurements from weather stations? I couldn't find any for Sweden

Re: Air quality monitors: paying more does not get you more accuracy

#66

Post by Leo_Germond »

pachico wrote: post #33

This is not a joke, I am really asking: how do you measure the accuracy of an air quality monitor? Comparing it to another monitor? Creating an air pollution condition and seeing how close to that is the measurement?

One way is to set up a flottila of sensors around a certified control sensor, such as an aerotrack, and measure how they evolve in regards to age, temperature, wind, level of pollutants, ans measurement time. That is a pretty rich task, because low cost sensors will vary wildly in performance due to mechanical variations.

Re: Air quality monitors: paying more does not get you more accuracy

#67

Post by Havoc »

To a point. Eg I bought both a bme680 and scd41.

Ie one co2 equivalent and one real one. The difference is sizable. Equivalent is basically garbage data. Correlates a bit with say opening a window but that’s about it

Esp in absolute values. The trend seems vaguely ok

Re: Air quality monitors: paying more does not get you more accuracy

#68

Post by supermatt »

ahaucnx wrote: post #3

Author here. I wrote this article a few weeks ago after discovering that a well known air quality monitor in the market that retails for more than USD 1000 actually uses a PM module that costs less than USD 20. Often people assume that the more expensive, the better but as you can see in the article this is often not the case -especially when it comes to the accuracy of the monitor. If you are looking for an open sou…

What is the difference between the indoor/outdoor kit? It seems the outdoor one contains more sensors but is less expensive? (or is this a nod to the article in some way ;))

My partner has a pottery studio with a kiln, it can get pretty smoggy in there when a firing is taking place (its unoccupied during, but it takes a while to settle afterwards), so I want to get a sensor. Are there any add-on sensors you can think of that would be useful in addition to assess off-gassing of VOCs (or something else?) from the kiln firing?

Re: Air quality monitors: paying more does not get you more accuracy

#69

Post by ffgjgf1 »

Al-Khwarizmi wrote: post #56
hammock wrote: post #18

Earlier quoted context omitted.

The same is true of digital bathroom scales. In fact almost all consumer grade digital scales have “fake accuracy” built into the firmware that ensures the same exact weight shows up when you step on the scale twice in a row, even if you pick up e.g a quarter-pound weight in your hand the second time

That should be outright illegal... Why do they allow equipment that deliberately lies to the user?

Because users want to be lied to?

Re: Air quality monitors: paying more does not get you more accuracy

#70

Post by nicbou »

Rebelgecko wrote: post #52
pachico wrote: post #33

This is not a joke, I am really asking: how do you measure the accuracy of an air quality monitor? Comparing it to another monitor? Creating an air pollution condition and seeing how close to that is the measurement?

The state of the art for reasonably priced CO2 monitors seems to be that they hard code in the "ambient" Co2 level and instructions tell you to let it sit outside every once in a while. The the sensor adjusts can adjust it's baseline accordingly , assuming that the lowest CO2 level it's seen in the last week or so is equivalent to the "ambient" outside level. Ofc this is susceptible to issues and can require even mor…

That last sentence was a punch in the gut
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