Don't forget about a concept called 'sick building syndrome'
The bottleneck might be the air in the room
421–430 of 499 posts
Re: The bottleneck might be the air in the room
#422Earlier quoted context omitted.
Dissipation does not happen instantly. I’ve done development on products with CO2 sensors and I’ve spent a lot of time with them on my desk right in front of me and also off to the side. Readings right in front of me are predictably higher. You can breathe into a CO2 sensor 18 inches from your mouth and watch the values spike upward.
I generally have fans around, but I too use a CO2 detector in my home and have tested it in various places and situations. CO2 concentrations are not as localised as you are making them out to be. If they are elevated in front of my face, for example, I can also similar numbers just above and slightly behind my head. If you go outside and do it, you’ll be surprised that the number doesn’t move really change at all wh…
> And, spoiler alert: if the entire area in front of you has an increased CO2 concentration, then your environment has an increased CO2 concentration. That’s the entire point.
I don’t think you’re reading the discussion: The CO2 thresholds that people use are based upon ambient air.
The closer the measurement to your mouth, the higher the reading will be. It should be apparent why putting the sensor directly in front of your mouth will register higher numbers than having it across the room.
CO2 does not instantly diffuse throughout a space. If it did, it would be sufficient to have only very small air leakage in a space for the CO2 to diffuse out of it very rapidly
Re: The bottleneck might be the air in the room
#423Earlier quoted context omitted.
The comment was about the accuracy of the sensor, not about raising CO2 levels across the globe.
Sure. It just draws attention to the fact that a throwaway piece of advice for checking calibration of a CO2 sensor is ‘it should read 400-450ppm outside’ when a few short decades ago that advice would have been ‘it should read 300-350ppm outside’. It’s like if someone said ‘you can check if your chatbot’s news feed is complete and up to date by asking it for ‘recent mass shootings’. There should be two or three in t…
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Re: The bottleneck might be the air in the room
#424If you want citations search my post history, but CO2 cognitive impact studies have a replication issue. We’ve been studying the impact of CO2 for decades, at much higher levels than you see in office buildings and have never recorded any cognitive impact (until many thousands of PPM) until the Satish study in 2012 and a handful of other studies that Satish was involved in. If you think about it for a second these st…
As an example of a negative result-- https://www.nature.com/articles/s41526-019-0071-6
Astronauts given two different batteries of cognitive tests showed no dose-response relationship to CO2 concentration
Re: The bottleneck might be the air in the room
#425If you want citations search my post history, but CO2 cognitive impact studies have a replication issue. We’ve been studying the impact of CO2 for decades, at much higher levels than you see in office buildings and have never recorded any cognitive impact (until many thousands of PPM) until the Satish study in 2012 and a handful of other studies that Satish was involved in. If you think about it for a second these st…
I've only seen legitimate CO2 concentration studies with small impact on sleep quality (>1000ppm ie unventilated rooms can cause 1-5% decline in sleep efficiency, observable as more nighttime wake ups or longer sleep).
Re: The bottleneck might be the air in the room
#426Earlier quoted context omitted.
You think that’s stopping CO2 buildup?
Lol yes
I laugh pretty easily myself :)
Of course some things are more hilarious than others :)
>Cars aren't hermetically sealed
I can agree with that completely.
Not my downvote btw, corrective upvote instead :)
Naturally I often wonder if many people know what Hermetically sealed is all about to begin with.
I do a bit of that in the lab when I seal flammable reference materials inside glass ampules using a torch. But it's not the sealing that counts, it's the technique ;)
If you check Wikipedia, you may notice that the terminology is older than the internet in every way.
Specifically they do not show awareness that it really means "sealed in such a way that it can't be figured out. As if by God. Not just any God but the ancient Roman God Mercury, otherwise known as Hermes when worshipped by the ancient Greeks."
Now I can only assume you have never been in a new 1960's WV beetle when all windows and the manual vents were shut (they didn't have A/C) when somebody slammed the door. You eardrums would remember it if so.
Re: The bottleneck might be the air in the room
#427Earlier quoted context omitted.
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. I…
> 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.
I've got a NDIR CO2 sensor about 6 weeks into a supposed 1 year battery life, still reporting 100% battery. Power use is very low since it only fires up the CO2 sensor every 30 mins.
Re: The bottleneck might be the air in the room
#428Two tips: if you want a stationary CO2 meter in a room, you can make one very cheap with a SenseAir S88 sensor (22 Euro) and hooking it up to an ESP board. Flash ESPHome and you can get live statistics in your Home Assistant dashboard. The S88 is a pretty good optical NDIR Sensor that auto-calibrates by putting it in the outside air or in a well-ventilated room every N-days (N is in the data sheet). A bit more info a…
Thanks for mentioning that, last week I got 2 SwitchBot hub mini, 3 temperature sensors each, for 70€ total, they are really neat. Even put one in our fridge, I didn’t expect the signal to pass but it’s working :) Will look at adding the CO2 monitoring Edit: actually, they only sell them as part of a 6-in-1 device, with a display, and a bunch of other sensors. That feels overkill, I wish they would just sell the CO2…
I have a SwitchBot Meter Pro CO2 that is just temp/humidity/C02. Works well and was inexpensive ($50 or so).
Re: The bottleneck might be the air in the room
#429If you want citations search my post history, but CO2 cognitive impact studies have a replication issue. We’ve been studying the impact of CO2 for decades, at much higher levels than you see in office buildings and have never recorded any cognitive impact (until many thousands of PPM) until the Satish study in 2012 and a handful of other studies that Satish was involved in. If you think about it for a second these st…
The difference between Satish-involved studies and other studies is extreme, too. Their first 2012 study tested levels at 600, 1000, and 2500ppm. In many categories they observed the 2500ppm group receiving "dysfunctional" ratings in their tests. Even their 1000ppm group saw significant drops.
This sparked the panic about CO2 levels that led to people buying CO2 sensors and thinking that not unusual CO2 levels were actually destroying their ability to think. Many conclude that this has been happening all of their lives and to everyone around them who is unaware.
It triggered a lot of follow-up studies. Confusing, some of those (like the Harvard one everyone cites) included Satish, meaning they weren't independent despite coming from different organizations.
The really interesting thing is that many of the follow-up studies that don't include Satish have even used CO2 levels much higher than the 2012 study that caused the panic. Here is one I grabbed at random that went all the way up to 15,000ppm and failed to find any significant changes: https://pubmed.ncbi.nlm.nih.gov/29789085/
There was also a lot of CO2 research before Satish come along that failed to find significant effects at these relatively low levels. It has been researched in the contexts of air quality for submarines and space shuttles by militaries and NASA because keeping the crew of those operating optimally is important, clearly.
Re: The bottleneck might be the air in the room
#430As a high school teacher, I first noticed this effect when I started using a CO2 monitor in my classroom as a proxy for air freshness during COVID. The CO2 levels in our supposedly "no problem with the air" classrooms shot up to 2000 ppm within minutes of the start of school and stayed there all day. Kids weren't checked out ONLY because I teach mathematics. They were breathing bad air, too. Worse, when I brought the…
Most studies don't register cognitive changes in the range of 2000ppm. A lot of the military and space studies used exposures multiple times higher than that without registering cognitive problems. It wasn't until you got to very high numbers that they registered any changes.
Only a couple studies purport to show cognitive changes at levels around 2000ppm, and the ones I know of all involve one controversial researcher named Usha Satish.
There are a lot of studies with CO2 levels at 10,000ppm or higher that have failed to find cognitive effect (an example https://pubmed.ncbi.nlm.nih.gov/29789085/). Your 2000ppm classroom air would have been like fresh air relative to the concentrations these studies are looking at.