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Training my sense of CO2 ppm

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Re: Training my sense of CO2 ppm

#41

Post by scottlamb »

abirkill wrote: post #37
CoastalCoder wrote: post #7

I think the elephant in the room is calibration of the CO2 detector. When I looked into this a few years ago, I couldn't find any accuracy guaranties for CO2 meters marketed for households / greenhouses. The closest thing I could find were laboratories that could test CO2 meters in chambers with known CO2 concentrations. But IIRC the pricing for those labs was prohibitively expensive. - There were literally no guaran…

The auto-calibration systems on cheaper consumer sensors also cause issues if they rarely see air that has low CO2 levels. Because these sensors can't measure absolute CO2 levels, only relative CO2 levels, they provide an absolute figure by looking for the lowest CO2 concentration they've seen over a period of time, usually around a 72 hour rolling window. This works acceptably if the sensor is frequently exposed to…

> Unfortunately, when I last looked, I couldn't find any consumer-grade sensors which used dual-NDIR sensors, only more expensive and less aesthetic commercial sensors. In the end I built my own using a CDM7160 sensor connected via I2C to a ESP8266, which reports over MQTT.

Looks like that's been discontinued. [1] Any advice for folks trying to build one now?

[1] https://www.figarosensor.com/topic/2020/11/Discontinuance-of...

Re: Training my sense of CO2 ppm

#42

Post by abirkill »

scottlamb wrote: post #41
abirkill wrote: post #37

Earlier quoted context omitted.

The auto-calibration systems on cheaper consumer sensors also cause issues if they rarely see air that has low CO2 levels. Because these sensors can't measure absolute CO2 levels, only relative CO2 levels, they provide an absolute figure by looking for the lowest CO2 concentration they've seen over a period of time, usually around a 72 hour rolling window. This works acceptably if the sensor is frequently exposed to…

> Unfortunately, when I last looked, I couldn't find any consumer-grade sensors which used dual-NDIR sensors, only more expensive and less aesthetic commercial sensors. In the end I built my own using a CDM7160 sensor connected via I2C to a ESP8266, which reports over MQTT. Looks like that's been discontinued. [1] Any advice for folks trying to build one now? [1] https://www.figarosensor.com/topic/2020/11/Discontinua…

That's a shame, they've worked well for me. Unfortunately I can't recommend any others without doing some research, I found quite a few dual-NDIR sensor modules when I was looking and chose this one primarily based on availability and a reasonable datasheet.

A sibling post[1] mentioned a sensor that is listed as being dual-NDIR so should give reliable readings, and has a USB interface, so that sounds like one possibility.

[1] https://news.ycombinator.com/item?id=32122301

Re: Training my sense of CO2 ppm

#43

Post by kadoban »

danans wrote: post #25
kadoban wrote: post #20

Earlier quoted context omitted.

Interesting, I don't think I knew that was an option. I'll look into it, thanks. I rent right now, which means I doubt I can, but hoping to buy soonish.

If you do this (install an HRV), expect it to cost many thousands, and make sure all your duct-work is running through very well insulated spaces, or you will obviate the heat recovery part, and you will just have a very expensive ventilator.

Yeah, I'd assume it'd have to wait until I'm going to replace an hvac system anyway. But in my price-range of homes, that's fairly likely to be ~required anyway.

Sounds like something that would be worth it, I spend almost all of my time indoors and we have pets pumping out co2 as well.

Re: Training my sense of CO2 ppm

#44

Post by simondotau »

moduspol wrote: post #24
macNchz wrote: post #12

I've had an Awair monitor for a few years and enjoy keeping a fairly close eye on the numbers, but from what I've experienced so far I'm convinced sure I'd be able to train myself to discern CO2 levels. If anything it has mostly just encouraged me to open the windows, even just for a bit, whenever possible, and to always use the kitchen exhaust fan with our gas stove (and motivated me to buy an induction range in the…

Same here. I was truly surprised at how fast the CO2 goes up with our gas stove on. The only thing worse is when we use our unvented gas logs in the fireplace. We're switching houses next month and I'm seriously considering putting in an ERV. It's just a little tricky to explain to friends and family because it kind of makes you sound like a crazy person. But CO2 is measurable! And there is clear science about bad ef…

PM2.5 is also measurable and is arguably the greater long-term concern to human health with respect to indoor combustion.

(Not to mention the physics of fireplaces makes them counter-productive. They are effectively air pumps which suck in the warmest air inside your home and send it up the chimney. And that air has to be replaced from somewhere, most likely bitter cold outdoor air, through the many concealed cracks and crevices in your home.)

Re: Training my sense of CO2 ppm

#45

Post by tgsovlerkhgsel »

MatteoFrigo wrote: post #36
rootusrootus wrote: post #11

Earlier quoted context omitted.

The Aranet 4 claims it can measure up to 5000 ppm with +-3% accuracy. But you'd have to take their word for it, I guess. For $250 I'm hoping it's not a crap sensor.

The usual convention is that the accuracy refers to full-scale measurements. I.e., your device has an error of +-3%*5000ppm = +-150ppm. At ~400ppm you are about 37% off. Human exhaust breath contains about 5000ppm CO2, so this device is decent for measuring humans. It's less decent to measure atmospheric CO2. Edit: looking at the datasheet, the device claims +-30ppm and 3% of reading, which I interpret as "whichever…

I interpret the error as a sum, i.e. at 500 ppm, an error of up to 45 ppm (30+0.03*500).

Re: Training my sense of CO2 ppm

#46

Post by simondotau »

dQw4w9WgXcQ wrote: post #38

We need a study on what will kill you sooner, the CO2 levels or the need to anxiously monitor whether CO2 levels are too high in every single enclosed space you enter.

Nothing wrong with a little anxiety if it serves as motivation towards a healthier life — whether that be diet, exercise, or a healthy environment.

Besides, as a society, we have access to orders of magnitude more information than ever before and life expectancy doesn’t seem to be suffering for it.

Re: Training my sense of CO2 ppm

#47

Post by PragmaticPulp »

kadoban wrote: post #5

Is there any kind of CO2 scrubbing that's at all practical for home? I'm curious what the effects would be of going below ambient/outdoor levels, especially since those are rising (if slowly).

You wouldn’t scrub the CO2. You would use an Energy Recovery Ventilator or Heat Recovery Ventilator to supply fresh air without impacting air conditioning too much.

Or if the temperature is right, just open a window.

Re: Training my sense of CO2 ppm

#48

Post by PragmaticPulp »

CO2 concentrations are an ongoing topic of debate. There are studies that show no measurable cognitive changes up to CO2 concentrations in the thousands of PPM, while other studies seem to show cognitive changes at much lower amounts.

I tend to think that people with CO2 sensors tend to over-focus on CO2, when really what they’re feeling is the general stuffiness of a room. CO2 isn’t the only thing that accumulates in the air in an enclosed space, but once you have a CO2 meter in hand you might think it’s the only thing that matters.

That said, CO2 levels can be used to somewhat estimate the amount of rebreathing going on in a space. That is, the amount of air that you breathe in that has been exhaled by someone else. It’s not entirely pleasant, which can explain why people feel like they don’t like high CO2 levels

Re: Training my sense of CO2 ppm

#49

Post by robocat »

post-factum wrote: post #3

I've bought [1] and coupled it with Zabbix using [2]. Now I have a pretty realtime graph and a strong reasoning to air my room more often. [1] https://www.tfa-dostmann.de/en/product/co2-monitor-airco2ntr... [2] https://codeberg.org/pf-monitoring/airco2ntrold

Amazon link: https://www.amazon.com/CO2Meter-RAD-0301-Mini-Monitor-White/...

Artwork slightly different, but appears to be same product: “Using NDIR CO2 Sensor Technologies; Technical Specifications: CO2 Measurement Range: 0-3,000 ppm; Response Time: < 2 Minutes; Accuracy: 0-2,000 ppm ± 100 ppm or ± 7% of reading; Sensor Life Expectancy: 15 years”.

Re: Training my sense of CO2 ppm

#50

Post by fuzzfactor »

CoastalCoder wrote: post #7

I think the elephant in the room is calibration of the CO2 detector. When I looked into this a few years ago, I couldn't find any accuracy guaranties for CO2 meters marketed for households / greenhouses. The closest thing I could find were laboratories that could test CO2 meters in chambers with known CO2 concentrations. But IIRC the pricing for those labs was prohibitively expensive. - There were literally no guaran…

>pricing for those labs was prohibitively expensive.

It's good to have reference instruments like chromatographs and infrared analyzers, where I could use reference gases to calibrate and verify.

OTOH very low-cost sensors could be ideally suited if well designed with accompanying electronics, but ultimate calibration would require the same expensive laboratory materials for reference.

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