Air Quality Monitors Compared: AirGradient vs. Purple Air
airgradient.com
airgradient.com
Important is that you can adjust the automatic baseline calibration duration if you operate the sensor in a closed space that does not regularly get fresh air. Ideally put it into a longer period like 30 or 90 days or switch off and manually calibrate it regularly. I believe not many monitors offer that flexibility out of the box.
If you have some basic electronic skills, you can actually look at our open source build instructions and just build the basic monitor with the CO2 module [1].
https://www.amazon.com/dp/B07YY7BH2W
I bought one for myself, fine, then two for my siblings. The two I bought them always measured about 100 apart, when right beside each other.
To say – use the measurements as a comparison of what you know.
Maybe this isn't enough for you, but I know it's easy for me to get trapped in a rabbit hole of how to solve things in a specific way and at times I need to pull back and say "what am I actually trying to solve". I had this with co2 monitors, getting fairly into which one to get then I realised I can deal with this by just regularly opening the window. I don't need a specific number.
edit -
Air exchange may happen pretty quickly, depending on the room and surroundings, so it could be as easy as "every X minutes we take a moment to open the door and window".
They have self calibration routines that assume they see atmospheric CO2 levels at least once either per day or per week
If it's always inside that assumption is wrong and it will always report lower than true CO2 levels.
It looks like they've slightly improved the features and dropped the cost more on their followup model https://www.co2meter.com/products/co2mini-indoor-air-quality... this is not going to be lab grade accurate but if it works as well as their old one it's great for the price and fits your requirement.
- AirThings View Plus
- Sensiron CO2 Gadget https://www.sensirion.com/products/catalog/SCD4x-CO2-Gadget/
- Kickstarter: AirSpot https://www.kickstarter.com/projects/airspot/airspot-the-per... (uses the Sensiron sensor)
.. pretty much all instrumentation requires semi regular calibration, it varies by how often and how serious you are about exact results.
Many CO2 meters are sensitive to dirt | dust | crud build up ( see article ) and should be reset semi regularly as per the manual (or by the linked site guidelines if you've gotten a cheap one with no documentation).
PM I have something that shows air quality and it shows 0 and high at the same time as the Qingping
So often there is not too much difference in the accuracy of the monitors. I wrote about this some time ago [1].
However when it comes to data ownership, API access, costs and repairability that's where there are big differences. In many reviews these aspects are in my opinion not enough covered.
[1] https://www.airgradient.com/blog/most-aq-monitors-use-same-p...
It’s got the PMSA003 which doesn’t seem to be used by anything else on that list, though I’m guessing from a quick glance at the spec sheet is substantially similar.
Part of why I went with this one was because it was relatively open. They do offer a cloud service and things most people would expect, but the device will work out of the box with no account or internet connection. Mobile app works too. It stores some historical data on the device so you still get nice graphs and charts.
If you punch the device’s IP in a browser it gives you a page back where it dumps all the data back at you. There’s an actively maintained Home Assistant integration.
All the sensors are replaceable. Or swappable if you decide you would really rather measure something else later. (Don’t know about buying the component and soldering it on yourself, but they sell the sensors on the little daughter boards that can be swapped.)
Only real downside I can think of is… it’s not particularly cheap.
Mostly just mentioning it in case it ends up on some of those charts later. ;) Biggest challenge with any of these measurement devices is… I have no reference to compare to or any way to evaluate the accuracy. (Lemme tell you about the time I tried to measure the humidity around here… I now own a psychrometer as a reference device since I figured that’d be pretty hard for any manufacturer to fuck up _too_ badly.) I’d definitely be curious to see how it stacks up.
That said, I have definitely considered an airgradient and the esphome firmware.
They are open source, and provide the code source of their software as well as for the hardware, which is very rare. I have plan one day to build my own outdoor monitor based on their plans (as a project I don't have the usage)
The levels go above 1000 ppm in less than an hour with both of us in there.
Opening the windows to ventillate doesn't really solve this, as you'd need to keep opening and closing them every hour. I'm thinking about installing a HRV system, but struggling to find a model that could be integrated into Home Assistant. (ERV not necessary as I live in a european country with temperate climate, the humidity is mostly OK)
In the meantime I have two windows tilted open permanently in another room with the doors open. This keeps CO2 under 1000 ppm, but pretty bad for energy efficiency.
Overall pretty happy with the product, definitely made me much more aware of the air quality. I want to build a portable one with a display and logging to check out the car, the office, maybe the hotel rooms on a trip, the plane, etc.
https://www.sciencedirect.com/science/article/pii/S036013232...
Carbon dioxide is one of just a very few air quality problems for which you have strong inborn biological detection systems. If you don't feel like it's suffocating you, it isn't.
Based on every article I found, above 1000 ppm clearly affects sleep quality, cognitive performance, it causes headaches, etc. so 3600ppm is generally considered really bad.
Even if CO2 would be harmless in itself, it is a good indicator for bad ventillation.
Sleep quality and cognitive performance are often difficult to perceive in yourself.
Headaches aren't like that at all. If every article you found states that CO2 above 1000 ppm causes headaches, that should reflect poorly on everything else in all of those articles.
> Even if CO2 would be harmless in itself, it is a good indicator for bad ventilation.
This is perfectly true.
It appears the Purple Air uses the Bosch BME688 while the AirGradient uses the Sensirion SGP41.
I’ve used the Kaiterra Laser Egg for detecting VOCs previously, as well as some off-brand handheld device off Amazon. They mostly agree.
"The testing results show that the SGP41 has a better response for 9/10 tested VOC solvents and can detect the level of NOx gases, which is a unique and important feature for hazardous and toxic gas detection and alarm systems."[1]
In general measuring VOCs is quite challenging and people really need to understand these type of sensors. A couple of months ago, I wrote a whole blog post about these issues. [2].
SGP41 algorithm is open source, BME is closed source, requires you to link a binary during compilation.
In theory BME can sample additional gas profiles (programmable heater waveform), in practice it's useless.
I agree that the SGP41 has better sensitivity, and also faster response and better stability.
The results I've seen for methane is discouraging, to say the least. Now moving to a NDIR sensor. A completely different thing, I know. Guess I was under a spell, it sounded too good to be true - a BOM cost reduction of 20x, and it was. I can go on and on about this one and the driverlib for it, but I've spent enough energy already.
If you have a basement | enclosed space in a granite rich area then you'll probably get radon gas pooling in that space unless it's sealed and|or vented.
You're unlikely to have an unspecified gamma source (lump of uranium, limp of potassium, lump of thorium) in your basement so ...
A generic geiger counter (click counter) should give a reading (low) outside your space in the open air, and another reading (higher) inside that space .. that can vary with time (as gas is expressed, pools, vented).
That generic click difference is almost entirely radon .. you'll be taking readings within 20 feet, one inside, anothe outside.
So you can easily get away with a cheap geiger counter to indicate if there's an issue .. if there is, you'll need to either:
* minise time spent inside space, and|or
* vent the space (fan blower, + pipe to outside)
* accept a cancer risk ~ a pack a day smoking if you use space as an office.
Source: a couple of decades geophysical surveying making radiometric maps of entire countries.
but radon is emitting alpha particles ?
These are all indicators.
Identifying radon is either a stochastic puzzle or a job for a mass spectrometer.
If you're concerned about radon the best bet is to either move or to mitigate
https://en.wikipedia.org/wiki/Radon#Testing_and_mitigation
it's a heavy gas that "oozes" out of granites and settles in low areas .. valleys until a breeze comes through or basements until pumped out ( floor level extractor fan | gas sump ).