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I would hesitate to say the IKEA is worse. Inside the IKEA is a reputable Sensirion all in one sensor module. It's much cheaper and smaller because the CO2 sensor in it is using different (newer) technology that only released a few years ago from Sensirion.

(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)

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Worse specs? Sure. Worse value? I don't think so. Worse accuracy? Perhaps not either.

A price of 30 EUR makes this sensor really easy to pick up. For the same price as one Aranet (~180 EUR) the typical household can place a sensor in every room of the house. Which provides far more accurate readings for the whole house than just one high-end sensor in one room.

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I have one IKEA Apstuga on my desk, sitting right next to a good CO2 monitor. Since Apstuga uses worse approach (heat) rather than light as the good sensors, it diviates around +/- 100 ppm. For example the correct CO2 is 610 ppm and IKEA's sensor shows 552 ppm with is reasonably close. So the trend will be correct and the values will not be.

But when it goes over the safe limit it should be enough to decide to ventilate.

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No, it is crap. Yes, it is Sensirion, but it uses a thermal conductivity sensor, which is a very indirect method of measuring CO2. One part of the sensor emits heat and the other senses it and the idea is that heat transfer changes with different CO2 concentrations. However, a lot of other factors influence this as well, such as ambient temperature/humidity (which is why the sensor incorporates measurements from an SHT sensor), but also gas mixture, etc. You only get good readings at lab conditions. Even below 1000 ppm, I would often see readings that are 300 ppm from more expensive, known-good CO2 meters.

If you want a CO2 meter on the cheap, either wire up an optical NDIR sensor like the SenseAir S88 (22 Euro) up to an esp32, which is possibly the best sensor you can get for the money (slightly cheaper version of the sensor that the AraNet4 uses). Or if you want something standalone with a display, get the SwitchBot Meter Pro CO2 for ~50 Euro, which uses a photoacoustic NDIR, but is still miles better than the sensor in the ALPSTUGA. Can also be hooked up with HA through an ESPHome BLE proxy or with the SwitchBot Hub.

You can find a comparison of the IKEA sensor with other affordable sensors here:

https://danieldk.eu/hardware/smart-home/ikea-alpstuga

(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)

You forget to mention that it is ±100ppm plus ±10% of the ambient ppm, which makes a big difference. At 1000ppm it's ±(100ppm + 0.10*1000) = 200ppm and that's only in an environment with 25C, 50% RH, and 1013 mbar. So, that does not tell you much, given that thermal conductivity is very sensitive to environmental factors.

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if you just want to know if CO2 is too much, 300ppm precision is fine.

I dont need to know the exact level, just give me a green/yellow/red LED and make it cheap so I can have a sensor in every room

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No, it's not. You generally want to ventilate an office when you reach 1000ppm, but then the IKEA will often warn you already at 700ppm. 700ppm is fine.
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"Generally" is a vibe measurement to begin with. You won't notice any difference at all between 700ppm and 1000ppm. It's once you start hitting 2000ppm you are getting noticeable brain fog.
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Had bad ventilation in my old apartment (built 1888) so got a co2 monitor. Started feeling the effect at 1100-1300ppm, so would open it in home assistant and check, never below and never above really. During winter when it was -10 so couldn't keep the window open all the time.
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I disagree. I feel a very steady and progressive deterioration starting at 600 ppm. It becomes significant at 800 ppm. The studies back up the latter threshold.
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Unfortunately it will be hard for you to know how much of that effect is placebo. Unless you tested this with some kind of double-blind setup.
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You're not wrong, but indoor CO2 at these sub-1000 levels is a useful proxy metric for bioeffluent VOCs which are an objectively tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
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You would not notice a difference if you weren’t checking the CO2 ppm. You primed your brain to ‘feel’ the effects of higher CO2 by reading a study and are experiencing the nocebo effect.

If it makes you feel better I don’t see a problem with it.

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Indoor CO2 is likely overrated here at these sub-1000 levels but it's a useful proxy metric for bioeffluent VOCs which are a tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
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you assume that the error will always be in one direction

and if sometimes you ventilate a bit sooner than required, at 700, what?

businesses will not put $200 meters in every room

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Have you looked at the prices of meeting room furniture? A $200 meter is not a significant cost measured against what it costs to furnish the room in the first place. It only becomes significant is you treat it as a line item disconnected from the room it's in
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businesses will not put $200 meters in every room

There are good $50 Euro meters. Besides that, I am not sure if that is true, at my wife's workplace, they put high-end CO2 meters in every larger room where multiple people meet. Admittedly, this was during COVID, so a lot of organizations were using CO2 levels as a proxy for finding whether a room was properly ventilated.

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Presumably there is still the need to ventilate. So the concentration can also be measured more centrally. That is how the mechanical ventilation unit in my house works. For both humidity and CO2.
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$200 is nothing compared to the lost productivity.
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You put one CO2 sensor in the return air duct and tie it to outside air control.
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You generally want to ventilate almost continuously, so if a circulation fan kicks on at 700 instead of 1000 that's really not a big deal.
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But if I open a window at 700ppm, so what?
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Maybe you live in a place where the room temperature is the same as outside. Here in winter, it means sitting in the cold.
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Suddenly there's not enough CO2 in the room and you get overly awake! Bummer! /s
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I got the ikea sensor, I’d say it’s way more accurate than you need for personal use. I wouldn’t use it as a scientific instrument but it’s well good enough to see if the room is ventilated enough.

I was shocked to see just how fast CO2 climbs while in a room, and how just opening the window just a crack was enough to restore the room to baseline co2.

The thing runs on usb 5v so the power consumption is negligible. It also plugs in to home assistant great.

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I have HA send me a notification to ventilate my office when the air reaches 1000ppm CO2. The IKEA ALPSTUGA is often off by 300ppm even under 1000ppm. If I'd use it, I'd be getting notifications at 700ppm.

It is a thermal conductivity sensor, which is a very indirect way of measuring CO2 and is very sensitive to environment factors. You only get somewhat good readings in lab conditions.

Don't by the ALPSTUGA for anything but very rough trends, there are much better affordable options.

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Within 300 ppm is more than good enough. Realistically 1000 ppm is not that bad. The average meeting room is multiples of that.

Also in my experience it’s much more accurate than that.

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I notice that thinking becomes less clear when going above 1000ppm, so I let HA send a notification at 1000ppm. With ALPSTUGA it would send already at 700ppm. By the way, above 1000 the divergences become even larger due to the inaccuracy also being 10% of the ambient CO2 concentration (in optimal circumstances, probably larger IRL). So, suppose you want to be notified at 2000 ppm, the IKEA sensor might already do so at 1500 or 1600 ppm and it continuously drifts, so it's not like you can use a particular offset.

Besides that, what's the point? There are much better meters in a similar price class. As an additional benefit, they can last months or up to a year on two AA batteries.

ALPSTUGA is an inferior product.

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Can you recommend some?
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>With ALPSTUGA it would send already at 700ppm.

"oh no I am getting too much fresh air"

I get your point but come on.

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In some situations it means opening a windows, with big temperature drops when it is cold outside.

At any rate, this is really a weird discussion, because you can get far more accurate meters at similar price points. Why waste your money on a much worse meter?

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Can it work with Zigbee network or is Matter/Thread required?
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I'm using a bunch of IKEA's "smart home" stuff, all via Zigbee+HA, works great. Look for the Zigbee icon on the package, and the pairing for Zigbee vs their own home controller might have slightly different pairing sequence on the device, otherwise it just seems to work.
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ALSTUGA does not work with Zigbee.

They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter. Some of the new devices (mostly those who support TouchLink, e.g. some of the lights) have a secret pairing mode with which you can use them with Zigbee, but it's only a subset of the new products.

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> They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter.

Uuh, seems not keeping up with social media finally backfired. That sounds horrible! So far IKEA been a great experience when it comes to HA+Zigbee stuff, and I started buying stuff relying on they'd keep just keeping up with that, really sad to hear they've changed course.

The "secret pairing mode" stuff sounds the same as currently/before though, but they only do so for a subset is new and hope they again change their mind.

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Thread is significantly better. Zigbee relied on proprietary hubs and apps or hacky work arounds. Matter over thread devices don't need a brand specific hub or app. You can literally control the new ikea products direct from a modern iphone which includes a thread radio, no hub, server or app required.

If you already own the ikea hub, they secretly put thread radio in it which was just sitting unused in preparation for this range.

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It's complicated. Matter over Thread is indeed nice in that it you only need generic Thread and Matter servers. It also makes it easier to share credentials between ecosystems. Thread itself is also a pretty nice standard technically.

There are also strong downsides though, one is privacy and future cloud lock-in. Zigbee is fully local. Previous Thread standards added the option for NAT64 so that Thread devices can access the internet and there were some Thread + Matter devices that already require internet access for full functionality (IIRC some Nuki smart locks, but I might misremember). However, Thread 1.4 also adds support for Thread devices to get a globally routable IPv6 address. The Thread 1.4 whitepaper is pretty blunt about what this enables:

Simplified Cloud Integration: Thread devices can now seamlessly connect directly to cloud services, enabling remote control, monitoring, and over-the-air firmware updates.

https://www.threadgroup.org/Portals/0/Documents/Thread_1.4_F...

The fact that Thread and Matter are strongly pushed by Google, Apple, etc. should tell you enough.

Now, a TBR may simply allow you to disable NAT64 or globally routable IPv6 addresses (e.g. Home Assistant's addons), but many consumer implementations don't. E.g. the Apple TV is a Thread Border Router and does not allow disabling NAT64, so Thread devices can access the internet, send analytics, and can be cloud-controlled.

Also, the ecosystem is still pretty immature, as a result of which you can encounter issues, typically resulting in unstable device connectivity. E.g. TREL does often does not work well. Apple has some hacks to fix most of the issues, but it only works well between Apple devices. So it's generally the best to avoid combining multiple TBRs into the same network.

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> Thread is significantly better.

Better than what already exists and is deployed? I dunnno, hardware already in use always beat "hardware conceptually better but I don't have it", that's why Zigbee is better, for me. Protocols much like everything in the world, isn't correct/incorrect or universally "better", it's all down to use cases.

Personally, as someone who started to rely on IKEA providing Zigbee devices, Thread is obviously worse, because 100% of the devices I have are already Zigbee and not Thread.

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Ikea preemptively sorted this out by putting thread radio in their hubs years before rolling this out. There's also thread radios in the latest chromecast, apple tv, and loads of other products. If you have a single thread border router in your house from any brand you'll be able to connect to any thread device from any brand. Phones can also directly control thread devices without needing any network or hub.

It's a vastly better system and the transition period is so smooth because the smart home companies have been deploying the thread hardware for years before anyone started using it.

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smart home companies have been deploying the thread hardware for years before anyone started using it

Also worth mentioning that many modern Zigbee radios can also be Thread thread radios using different firmware. There are even multi-PAN radios that can do Zigbee and Thread at the same time. Some smarthome hubs use multi-PAN (e.g. Homey Pro), but it's generally recommended against now because of lower reliability.

The same applies to devices, e.g. some of the new IKEA devices work over Thread or Zigbee (Zigbee pairing is triggered using a non-documented sequence, presumably they added support for TouchLink). Or e.g. the Aqara FP300, which can be flashed with Thread + Matter or Zigbee firmware. It works because the same radio can be used for both protocols.

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This wasn't true for zigbee either. I used a zigbee usb stick with home assistant, could use any stick that was supported.
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Yeah, I bought a bunch of INSPELNING smart plugs when they were clearing out the inventory. The new GRILLPLATS switches are more compact though, which is nice.
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It’s part of the new range which is all matter over thread only. The existing ikea hub can do thread though.
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> The thing runs on usb 5v so the power consumption is negligible.

There’s a huge leap from that to the power consumption being low enough to be integrated into a smartphone, as demanded by OP.

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I don't think power use is the issue. I have this cheap CO2 sensor: https://www.domadoo.fr/en/devices/5882-heiman-zigbee-air-qua... which draws 0.5W. This includes thermometer and humidity sensor, Zigbee transmission, and acting as a Zigbee router, but it gives us an upper bound. It also measures continuously (picks up someone breathing on it within 10s), which is overkill. A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.

However, this assumes the sensor would fit in a smartphone, which is not a given. And these things need air flow. And they also wouldn't work while the phone is in a bag or a pocket.

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>A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.

Not sure about that, at least NDIR sensors have to be at certain elevated temperature to work and they do some preheating when you turn them on from standby.

So it's not possible to just measure less often as then energy would have to be spent on heating the sensor.

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Ruuvi Air[1] seems to be close to the middle in both price and CO2 measurement accuracy between aranet4 and the IKEA device. I don't have personal experience with Ruuvi Air specifically, but have been using their cheaper Ruuvi Tags (that don't measure CO2) for temperature, humidity and air pressure measurement at home and office.

[1] https://ruuvi.com/air/

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> I also don’t know how much electricity they pull.

It can't be much, since the Aranet 4 can run for years on 2 AA batteries.

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