Clean air, everywhere, for everyone. That’s what drives me to explore innovative ventilation & air quality solutions.
Joined September 2022
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CO2 sensor in a public place. An airplane, a library, a restaurant, a supermarket, a medical waiting room or other. `
No possibility of placing it 1 m from you or another person.
Where would you place it if you have the choice between your yoga pants, on a wristband, or in an open handbag, if you want to have the most accurate CO2 data?
Which of these 3 possibilities in your opinion overestimates or underestimates the CO2, according to you?
I have finished tests with CO2 sensors, 8 models that are compared to Aranet 4 used as a reference value. Humble open science, nothing very elaborate.
I would like to read your thought before I share the results
I don't want to say any more so as not to influence your answers
ALT ia generated image
1/CO₂ sensor tests.
Accuracy of 8 CO₂ sensors estimated against the Aranet4
(AirGradient ONE, AirSpotHealth, Qingping Air Lite, Qingping Air Monitor Pro 2, Temtop M10+ (2 of them), VisiblAir Model C, Inkbird Plus and Temtop C1)
Protocol, roughly: the sensors are aired out outdoors for 45 minutes before the test starts.
Did 2 accuracy tests.
Each test has 2 phases. In the "CO₂ rising" phase, I sit with the sensors in my small bathroom for 30 minutes, 1 m from me. In the "CO₂ falling" phase, I place the sensors outside on my balcony for 30 minutes.
Here are the raw results of the first test I ran, in the bathroom
next tweet, results once returned outdoor, on the balcony 👇🧵
3/Deviation from the Aranet4 for each of the 8 sensors.
Positive values mean CO₂ overestimation. Negative values mean CO₂ underestimation.
In the bathroom: AirSpot: 13.3%; AirGradient: 14%; QP Pro2: -15.9%; QP Airlite: 12.5%; VisiblAir Model C: -17%; Inkbird Plus: -4.4%; Temtop C1: 0.9%; Temtop M10+ (1st unit): -5.6%; Temtop M10+ (2nd unit): -3.6%
Outdoors on the balcony: AirSpot: -1.6%; AirGradient: 4.1%; QP Pro2: 7.6%; QP Airlite: 14.2%; VisiblAir Model C: -17%; Inkbird Plus: -13%; Temtop C1: 65%; Temtop M10+ (1st unit): 8.1%; Temtop M10+ (2nd unit): 42%
4/ A few preliminary observations from this first test
Temtop C1: before this test, I didn't know it could be set to measure every minute. In the bathroom, it was off from the Aranet4 by 0.9%, which is excellent. However, when placed outdoors, it never registered that CO₂ had dropped and stayed frozen at around 715 ppm. Maybe a temporary bug, I don't know.
VisiblAir Model C reads 333 ppm outdoors, the lowest of all the sensors. It overestimates by 17.6% in the bathroom and underestimates by 17% outdoors.
AirSpotHealth overestimates by 13.3% in the bathroom and underestimates by 1.6% outdoors.
AirGradient overestimates by 14% in the bathroom and overestimates by 4.1% outdoors.
And you, Do you notice anything else interesting?
More to come: I’ll continue with the rest of the test data tomorrow
Plenty of choice means healthy competition in the market, and it respects the ordinary citizen who is shopping for a purifier
I love the Chinese proverb Adam shared, it reflects well what i think about it, not in ventilation but in life in general.
I think it's up to ordinary people to make informed decisions for their own particular situation, based on their needs, their standards and their resources (space, money, the amount of noise they can tolerate, etc.).
It's not for us to decide for them which air purifiers they should install; thinking we know better than they do fails to respect their autonomy and free will.
What the market should offer is plenty of choice and transparency in the information provided to the public.
Be calm. I learned many years ago that I can't satisfy everyone. We need to set aside those unfriendly and unconstructive opinions and ignore them. Let me share with you a saying from 1,379 years ago.
Since twitter can auto translate, I will leave it in Chinese.
一场滋润万物的春雨，农夫因庄稼受益而喜爱它，行路人却因道路泥泞而厌恶它；一轮明朗的秋月，佳人乐于欣赏，盗贼却恨它照出了自己的行迹。
连“天地”这样滋养万物、普照万物的存在，都无法让所有人满意，总会有人因为自身的处境和立场而心生怨恨，更何况一个普通的人呢？
Brilliant, it blends right into the surroundings! And it looks beautiful too. Ingenious. Installations like this are the future of air purification. I'm guessing it must be quiet as well, since those look like PC fans
1/ Hey, community interested in air purifiers and open source DIY.
Air filter filtration % (efficiency): it’s better to measure than to guess.
A thread 🧵that I think is important, and that I invite you to read in full, about filters and % efficiency.
I’d like a serious discussion to start. For you to start questioning accepted ideas.
We need to revisit two commonly accepted ideas.
That the filtration % (% efficiency) of an air purifier’s filters is the same at all settings, and that we can just use the certified % efficiency to convince ourselves that it’s the same no matter which machine it will be used in.
That at a lower velocity, the filter’s % efficiency increases.
(note: Velocity = Flow rate / Filter Media Surface Area )
👇
8/ Note. Are my measurements 100% reliable? Absolutely not. I’m the first to want different testers to test the same things, compare our data and try to explain the differences.
But these measurements have the merit of being about the machines and settings actually tested. As I sometimes say: “it’s better to measure than to guess”.
A measurement isn’t automatically better than an estimate: that also depends on the method and its uncertainty. But a measurement made using an appropriate method, under the conditions we’re interested in, gives us more direct information than an estimate based on tests done under different conditions.
A filter’s spec sheet may report perfectly valid measurements. But using its filtration % to assign a filtration % to a machine, without testing it, is still an estimate. The conditions change. We haven’t measured that machine’s performance at that setting.👇
9/ Moral of the story. The devil is in the details.
Filter spec sheets aren’t bad in themselves. Some report real, properly measured % efficiencies. But those results apply to the conditions tested. We need to be careful about generalizing them to other conditions.
This is particularly important for 3 reasons.
1. Air purifier or filter manufacturers should back up filtration % claims with tests under the conditions they’re claiming those percentages for, including the machine’s settings. Or leave out % efficiency altogether and simply report the CADR measured in a lab.
Some people (including me a few years ago) estimate CADR from airflow and an assumed filtration %, using CADR = Flow × efficiency. Yet the same filter’s efficiency can vary from one machine to another and from one setting to another. In my tests, CADR has more often been lower than expected than higher. It’s better to measure CADR with a properly conducted decay test in a test chamber than to calculate it using airflow and an assumed filtration %. If you can only estimate, know the limits of your estimate and, above all, recognize that it is an estimate, not a measurement.
Some people use air purifiers with HEPA filters close to themselves for infection prevention, assuming that a HEPA filter will protect them better than a MERV13. But the filter label alone doesn’t tell us how the whole machine performs. In my tests, some machines using MERV13 filters had higher measured PM1 filtration efficiencies at certain settings than other machines using HEPA filters. Assuming that a machine removes over 95% of PM1 or PM2.5 just because it uses a HEPA filter can give a false sense of security if its actual performance hasn’t been verified.
I am going to state what I would have answered before testing. And later we'll see if my tests make me change my mind. I hadn't thought about the question very much, but I instinctively thought that a bracelet would have been the best choice, an open handbag the 2nd choice, and pants pockets the 3rd choice. I figured that pants pockets would underestimate CO2 way too much. That the open bag would also underestimate CO2, but not as badly as pants pockets. And that the bracelet would overestimate CO2, but the gap with the measurement taken at 1 meter would be more favorable than the other two options. That's why I bought the Airspot Health, based on this idea I had formed
"C'est la vie, quand l'été, tourne à l'automne"
I made this music and autumn color photo video montage back in 2018 while staying at a motel, as my love was at the hospital by her father's bedside. It uses photos taken during cabin getaways, around my place, on walks to visit my mother, or on my way to the clinic where I worked near my house (I used to walk through a park to get there) vimeo.com/295945933
j'adore les couleurs d'automne. Toute cette beauté éphémère que je ne veux surtout pas rater. ça me fait un effet physique, un baume au coeur et j'ai les yeux mouillés, rien qu'en regardant les arbres. Ils ont tous leur charme. Et j'aime regarder, à ce temps-ci de l'année , cette vidéo de musique avec un décor coloré. je vous souhaite de faire le plein du beau, pour ensuite mieux vivre le temps gris qui vient. youtube.com/watch?v=6u0DGIh3…
Masks in the hospital: when a patient has to justify wearing one, and a healthcare worker is so wary of a masked person that she asks for reassurance that they aren’t contagious.
A personal anecdote: Yesterday, I had a long, five-hour appointment at the hospital for imaging prescribed by Dr. Piché, a physician and long-COVID researcher, to investigate a potential diagnosis of gastroparesis.
They took images every hour after I ate a radioactive meal.
I was wearing an N95 mask. The technician asked me why I was wearing one.
Feeling a bit uncomfortable having to justify myself, I replied, "I’m susceptible to infections."
She said, "Oh, okay I just wanted to make sure you weren't sick."
I answered, "I’m not sick precisely because I’m wearing a mask."
It was a way to end the conversation and perhaps prompt her to reflect on the fact that she might want to be more concerned about the patients who aren'twearing masks at all…
Because that’s exactly what’s happening, it’s completely backwards. In a hospital, a place where infectious agents circulate, it’s the person taking steps to protect themselves who has to explain why.
And yet, my N95 protects her, too. If I wear a mask, I’m less likely to transmit anything to her, and she’s less likely to transmit anything to me. It works both ways.
Her response: "Look, I just want to make sure you aren't sick, you know?" As if I hadn't understood. I had understood perfectly well.
It’s this reflex that bothers me: the assumption that a mask equals being sick. One should be able to protect oneself in a hospital without having to reassure anyone else.
Well, that’s just one example, one specific person.
But I know many of you go through this.
Take my partner, for instance: at an event months ago, she ran into an old acquaintance by chance who, pointing a finger at her, rudely asked, "Why are you wearing a mask?" She replied that she wanted to protect me because of long covid, as well as herself so she doesn’t have to cancel her groups in her business. It was an unpleasant experience for her.