Typical CO2 Levels at Home Test
co2meter.com
co2meter.com
https://www.climate.gov/news-features/understanding-climate/...
Although CO2 levels do dip below 400 in some places under some conditions, normally 400 should be considered the new "floor" level.
AFAIK most non-serious co2 monitors (ie. the ones you get for the home/office) have auto-calibration. They assume that the baseline co2 concentration is 400 PPM, and they'll auto-calibrate themselves to that level based on whatever the lowest concentration they saw in the past few days. For most living spaces (eg. home/office), this works because they'll be vacated at least once every few days (more typically once daily) so you can assume whatever low you saw is the ambient level.
With no knowledge about how such sensors works internally, my VMC have an optional CO₂-monitoring-driver to automatically regulate the fan speed: even the vendor state it's not worth the money, it might spare few € in electricity but not more.
How do you know? Did you send your meter to a certified lab for calibration? With uncalibrated meters all you can tell after some experience is "probably higher than before", "probably lower than before". Consumer grade meters are worse.
How do you know your thermometer is calibrated? Your thermostat? Your speedometer? Did you have your computer monitor calibrated by a professional?
The CO2 meter has a self-calibration function that I've used that calibrates it to the baseline known outdoor PPM. Indoors, it is clearly responsive to the environment. And the readings correlate with noticeable changes in air quality. The primary interesting part about it is that it gives a clear indication of how long it takes for the air in the house to be exchanged by the vent fan and return to the outdoor PPM. I don't see how precise calibration really matters for this use case.
> "In a study conducted by SenseAir, they found that with 4 adults in a car, the CO2 level could reach 6,000 ppm even with the fresh air ventilation turned on. This is important to know, as between 10 and 30% of all automobile accidents are attributed to drowsiness."
That sounds like an extraordinary claim. There have been discussions on HN before about CO2 levels in classrooms and offices, and what it might cost for education and productivity, and discussions about if atmospheric CO2 levels approached thousands of ppm and lowered the effective intelligence of every living person. But they were speculative comments. This claim that inside cars it easily reaches into their "levels associated with complaints of drowsiness [...] headaches, sleepiness [...] maybe poor concentration, loss of attention" is significant.
They say 10-30% of car accidents are attributed to drowsiness, the NHTSA estimates 43k people died in car accidents last year, is that also 10-30% of fatal car accidents attributed to drowsiness? Or 4k-12k deaths/year? And compared to the billions spent on self-driving cars, how much is spent on ventilation and cabin CO2 monitoring?
[1] https://www.nhtsa.gov/press-releases/early-estimate-2021-tra...
https://www.hsph.harvard.edu/news/press-releases/carbon-diox...
The results are very interesting to say the least:
The findings showed that the pilots were 69% more likely to receive a passing grade on a maneuver when CO2 levels were 700 ppm compared with 2,500 ppm. When CO2 levels were 1,500 ppm, the pilots were 52% more likely to successfully perform a maneuver than when CO2 levels were 2,500 ppm. When the researchers compared the difference in pilot performance at 700 ppm and 1,500 ppm, the difference was not statistically significant, but they did find that pilots were more likely to successfully perform some of the most difficult maneuvers at the lower CO2 level. The study also found that the negative effects of CO2 on flight performance became more pronounced the longer the pilots were in the simulator.
By far the biggest source of CO2 in my house is the gas oven — its days are numbered!
This made me think about my device accuracy. With open door it is usually well below 400ppm (which seems to be an artificial lower limit of the device).
Finally, I think my device is ok - with door and window closed it gets to 800ppm in about 2-3 hours which seems quite reasonable.