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Comment by NikolaNovak | Hacker News Reader

Open source diy is wonderful. But is there a reliable trustworthy monitor that can just... Be bought? A box that will reliably tell me what's the carbon dioxide carbon monoxide dust allergens volatile compounds? Am I possibly being greedy and I need several konitors (I wouldn't have an issue with that)?

Every review I check for any consumer accessible device seems to indicate they're inaccurate, miscalibrated, or downright deceptive :-(

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I got the uHoo Air Quality Monitor[1] and I love it. One of the few nice smart-home/app ones to monitor carbon monoxide too. But it's pricey. I can probably get some discount codes from them if the HN community is interested (I've spoken with their team once before in Singapore and they were very nice and accommodating!)

[1] https://getuhoo.com/

Hey, have you tested it much? This evaluation site shows weirdly low r^2 values of 0.0, but maybe they just haven't evaluated it. http://www.aqmd.gov/aq-spec/evaluations

I own this one as well. I’ve been pleasantly surprised at how well it works and how quickly I can see changes when it alerts me to a CO2 buildup and I go open some doors. It’s satisfying to be able to see the effect fresh air has on my environment watching their charts.

I picked this one because it also monitors Nitrogen Monoxide which gas stoves give off which many other air monitors do not test for.

I haven’t tried their IFTTT integration though, that will be next.

I have this one too, but yeah, it was expensive when I got it and has only gone up. I also don't love the dependency on a remote cloud.

What I'd like is a box which would just host an HTTP endpoint on my wifi network, and respond with a Prometheus metric endpoint (maybe throw JSON in there so it can give a "device specific" super accurate response too).

Let the community worry about the rest of the integration.

Anything under $60 doesn't have a 'real' CO2 sensor. One of the good budget ones is Cleargrass Air Monitor.

You can diy for under 60 with a photoacoustic SCD41.

The Aranet has worked well for me, and I think is calibrated well and works smoothly. It’s not the cheapest though, but I haven’t recharged it in over a year… almost two years now!

https://a.co/d/9o1Qvzb

This is the right pick, because it has an NDIR sensor.

Yeah, I did a bunch of research before I got one. I was primarily interested in CO2. It was very interesting in the earlier days of covid-19, but it’s still interesting now, even around home. I have noticed how the CO2 level spikes to 1200 or more when I turn on my gas stove. That, along with recently learning about how gas stoves can cause issues for children, have me planning to get an induction stove very soon.

That one only does co2 though, am I correct? It would not help me with allergens or dust etc

Yes, CO2/temp/humidity only.

We have one in office, I think more than 2 years already and haven't changed batteries. Bought new one, compared readings and CO2 readings were matching.

Was trying to look whether old one should be recalibrated (per instructions, have to leave outdoors for a while every <don't remember> months). However our office CO2 is already ~600-700ish when people are here, so maybe it is fresh enough for recalibration.

Ah, and home-assistant integration is finally available for Aranet https://www.home-assistant.io/integrations/aranet/

Great product. You can get data into Prometheus with https://github.com/ryansouza/aranet4-exporter-go too.

The Airthings View Plus is a good one. It has high quality (for consumer) particulate, CO2, VOC and Radon sensors and a good interface. Also tracks temperature, pressure, and humidity for completeness.

For PM2.5, the Qingping Air Monitor (or the Lite version if you prefer that) is good. The review I've read found it has decent accuracy, and, though I haven't tested it rigorously myself, the readings seem reasonable in my experience. The main reason I recommend it, though, is that the UI is great: it keeps graphs of past values that are easy to access, both on the screen and in the app.

On the topic of allergens, I wasn't able to find any device that can measure that.

PM, CO2, temperature and humidity can be fairly accurately measured with consumer monitors provided they use good sensors.

You can check if the monitor is RESET AIR certified which is an independent and 3rd party test against reference devices.

https://www.reset.build/directory/monitors/air

There will be one from Ikea coming out [1], I'm currently waiting for that one after selling my Awair.

[1] https://www.notebookcheck.net/IKEA-VINDSTYRKA-smart-air-qual...

Be aware that its "predecessor" happily:

> shows you a green light until 35 μg/m³ which is SEVEN TIMES the WHO air quality guideline. It is also around 3 times what the US AQI regards as Good.

https://www.airgradient.com/open-airgradient/blog/ikea-vindr...

Check out the Purple Air community map and their sensors:

https://map.purpleair.com/?mylocation

https://www2.purpleair.com/products/list

What is wrong with an cheap device like this?

https://www.aliexpress.com/item/1005005011458177.html

$15 from AliExpress including shipping. If you are concerned about accuracy, could you not take it outdoors to see how it measures the unaffected atmosphere, then bring it back indoors to see how it compares? For instance, if you are concerned that the 900 PPM reading in your bedroom is inaccurate, you could take it outside and see how it reads compared to the expected ~420 PPM. You might be off by a few PPM, but would it not be accurate enough to see if you are approaching dangerous levels?

Sensirion CO2 Gadget is good with one of the best [small, reasonably priced] sensors (SCD41). Has BLE interface (with android/ios app). Only shows co2. https://sensirion.com/products/catalog/SCD4x-CO2-Gadget/

It does use auto calibration, which means you need to bring it outside for a few minutes every once in a while (7 days IIRC). Not doing it will not break it, but the readings will drift downward (sensor assumes that the lowest reading it gets in a period of time must be 400 ppm) - and will be fixed in a few minutes outside (few minutes of <400 ppm sets lowest reading to 400).

I highly recommend Dual-NDIR sensors that bring their own volume of calibration gas. Auto calibration is not practical in any serious indoor monitoring use case.

How would that work? Having one sensor sealed with reference gas does nothing to help the second sensor. Is there actually a dual sensor which shuttles the gas between them? Seems complicated.

it's a 2nd sealed chamber and shares some sensor parts. Some parts are different, so it's not perfect of course, but much better as the requirement of regular manual calibration. Sensirion SCD30 for example, where you can even see the Y shape of the gas chambers.

SCD30 also has autocalibration with outside air though?

I’m fond of the CO2 Gadget too, but the autocalibration function takes 7 days to kick in, during which it must be plugged in continuously. This makes it impractical for use as a travel CO2 sensor when moving between two locations at different elevations. E.G., I had my Gadget calibrated for CDMX (2050m), then travelled to SF (50m) where the Gadget read 800ppm outdoors. I left the Gadget plugged in outside for four days, but it never calibrated before I left. I corresponded with an engineer at Sensirion who said it may be possible to add manual calibration via software update, and created a ticket for their product team. I hope they implement that.

That's interesting. For regular use however this may not be a big deal, auto calibration has a secondary mechanism by which it will recalibrate in just a few minutes if ppm < 400.

So after 8 days plugged in, the sensor is sure to be calibrated incorrectly to inside air, then you take it outside and it recalibrates again to correct values within a few minutes?

Recently bought Netatmo Smart Home weather station, which comes with both indoor and outdoor modules. It measures air quality (CO2, PM2.5) along with temperature, humidity, air pressure, sound. It has its own app and can work with Apple HomeKit and Alexa. Happy with it as of now.

https://www.netatmo.com/en-us/weather/weatherstation

Pretty sure that Netatmo measures only CO2, not PM2.5. There’s no mention of PM2.5 on the link you posted.

Also, to properly calibrate the Netatmo needs to be exposed to essentially outside air once a week as it takes the weekly lower bound as its reference point. More sophisticated sensors don’t have this limitation.

I have been using the Awair for like 3 years, and it seems to work fine. I never did a test to compare it to other products, though.

Seems like airgradient has one https://www.airgradient.com/airgradient-one/

There's no pricing though and it looks like it's tied to subscription software.

I spent $30 on one and $20 on another. They're "close enough" and I could connect them to home assistant. The reviews suggests the CO2 is off by 100 ppm. I've only seen VOC measurable when it's in my garage.

It depends on your purpose.

There's also privacy, many monitors also record sound levels (like the Netatmo for example which is used a lot.) Many monitors send all collected data to their cloud.

Amazon has their own air sensor for Alexa that can do PM2.5

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