#300

[@daromee]

Incredible presentation ,as an Environmental Engineer who works with these types of sensors and many others I am highly impressed of your depth of knowledge in this field. Kudos !! you never cease to amaze me you have an incredible grasp of so many fields .

[@AndreasSpiess]

I am old and had a lot of time to learn ;-)

[@GRBtutorials]

Actually, the reason CO2 sensors are used for air quality monitoring instead of oxygen sensors has nothing to do with cost, energy usage, size or how complicated they are (though they are costly). It's because we're not interested in oxygen levels, as it's very difficult to lower the oxygen levels to any appreciable level unless a room is sealed with a lot of people, but CO2 itself is toxic in high concentrations, and it can produce dizziness, feeling tired, and other related symptoms, starting from 1000-2000 ppm (that's only 0.1-0.2 %! At those levels oxygen concentration would, at most, fall from 21 % to 20.8-20.9 %, not near enough for any appreciable effect). Here's a link to a Tom Scott video about that if you want to learn more: kzbin.info/www/bejne/Z3_LkKmupd6We6M.

[@AndreasSpiess]

I am not sure about the whole thing anymore. In submarines with atomic bombs on board and in the Space Station the CO2 level seems to be around 5000 ppm all year round. I hope, these guy do not loose their abilities to think... I would have been interested in the O2 level at the end of his test.

[@AndersJackson]

@@AndreasSpiess that is why the have tests before sending people down or up. :-) Another thing. In Soda generator, like Soda Stream, there are CO2 gas tubes. So there you also will have access to pure CO2.

[@subspace666]

@@AndreasSpiess not sure about subs if they use a hack to compensate like increasing o2 levels or playing with pressure , but for space your o2 expenditure is greatly decreased in low or no gravity situations ,so probably can tolerate much higher co2 concentrations kinda like sick people here with reduced lung capacity might not need supplemental o2 when not doing physical activities. if you use less oxygen your lungs have less gas exchanging to do.

[@GRBtutorials]

@Issac Anakin Yes, the police and KZbin mods are very interested in your hacking Instagram scam.

[@MaximumEfficiency]

I can't find anyone measuring o2 in different areas: forest, city, dessert, sea, cave, basement, apartment etc. that data could be interesting, why is nobody measuring that?

[@hypnagogio]

Just wanted to reach out and say thank you for the content you are producing. The quality is excellent. You are structured and follow a clear logic in your presentations. Great overall! Keep it up!

[@AndreasSpiess]

Thank you for your nice words!

[@AriBenDavid]

CO2 levels can go up to 7000 ppm in submarines and space capsules. These levels are tolerable, but the CO2 level is an easily measured proxy for the usually accompanying high levels of VOCs and other air contaminants . We once measured CO2 levels in a crowded art studio. The air was stuffy and oppressive. Levels were 4500 ppm. The room needed more ventilation. I have also measured levels outside when many trees were photosynthesizing. They were just above 300. "Ah, fresh air!" They can get even lower during the day in a growing cornfield. And, your breath might be 40,000 ppm!

[@AndreasSpiess]

Interesting information! I also read about the high levels of CO2 in submarines. This is why I thought, the oxygen level must be important in crowded rooms.

[@MaximumEfficiency]

did you measure o2?

[@AriBenDavid]

@@MaximumEfficiency Harder to measure but not usually considered an issue as CO2 is.

[@Sensirion]

Thank you very much Andreas Spiess for this great measuring CO2 tutorial and for evaluating our environmental sensors SGP30 and SCD30.

[@AndreasSpiess]

Thank you!

[@LarryKapp1]

yes just like you say - one of the new buildings where I worked had a CO2 sensor which was supposed to open up outside air dampers to bring in more air. But while the engineers had specified it and the controls company installed it - but they never calibrated it or made sure that it worked properly. So it did not really ever do anything useful. I was on maintenance but that was not my building and we were all just getting up to speed on how the new DDC HVAC systems were supposed to work and also too busy fixing the most blatant screw ups that the controls company left for us. No they never had anyone commission the buildings which did seem really stupid for multi- million dollar buildings. I wish I had seen your video many years ago so I could have fixed that CO2 sensor issue !

[@AndreasSpiess]

From my normal job I know: "Not tested means not working" ;-)

[@AJB2K3]

Again, another useful video and again you have helped me unknowingly with an unconnected project. Please keep up the good work.

[@AndreasSpiess]

Thank you. I will!

[@A38-d7y]

Thanks for yet another great video. I have been using the MH-Z19B in exactly this way, to alert when I need to ventilate the room. Has been working for over 2 years now without any problems. However I was not able to make it work on 3.3V, only on 5V. Second thing - i needed to turn off the correction (ABC) - otherwise the values would drift off considerably with time, especially if windows are rarely opened in winter. The SCD40 looks very interesting. Would like to try it out as well, I guess it should also have a reasonable power consumption to use it in battery powered device. Then you can even carry it with you everywhere))

[@AndreasSpiess]

You are right. Vcc is 5V. only the logic levels are 3.3 volt.

[@svrestless3425]

Nice video. You are an inspiration. I just used senserion TVOC and senserion CO2 sensor a couple weeks ago. I actually used your node-red videos as reference. Thanks alot for that btw. Anyways what was shocking for me where the tvoc readings when I 3D printed. They where off the charts, and and for sure not healthy.

[@joergherrmann3864]

I did a lot research on Voc sensors. Voc (mox) sensor are heavily influenced by humidity amongst other factors. That's why your sgp30 shows that high value during the night. Even very low changes in humitdy counts for some 100ppm voc. I'm not aware of any single implementation that is able produce values usable over a period for days or weeks. Yes, they respond to changes very good but not on a absolute level. Co2 (mhz19b) must be the primary indicator.

[@AndreasSpiess]

Good to know. I also trust the CO2 sensors more.

[@_adamalfath]

As always, nice no BS explanation. I hope in the next video you also explain the best sensor/method to measure air quality on workshop environment. Like source from solder fume, glue gun, 3d filament, etc. Can't wait!!!

[@AndreasSpiess]

The VOC sensors at least should show some of the "dangers". But I am no Chemist...

[@uwezimmermann5427]

As a German living in Sweden I have to point out that SENSEAIR is a Swedish company. I have recently been involved with them as being an opponent in a thesis defense which deals with the improvement of both their CO2 and CH4 sensors.

[@uwezimmermann5427]

I do not seem to find the online version of the thesis... www.miun.se/en/Research/research-centers/stc-researchcentre/news-from-stc-research-center-eng/News-archive/2019-10/bakhram-guynullin-presents-his-licentiate-thesis/

[@AndreasSpiess]

Thank you for the correction. I got it from a German viewer and did not check further...

[@tedenda]

Andreas Spiess I have been involved in a plug-in for ESP-Easy firmware for SenseAir S8 sensor. Look here: github.com/letscontrolit/ESPEasy/blob/mega/src/_P052_SenseAir.ino

[@thomascziesla3768]

Nice to see that I‘m not alone to point out CO2 monitoring in schools! At the school of my kids I‘ve implemented a project making CO2 traffic light using MHZ19B sensors and RGB LED. After making some prototypes the teachers took over the idea and they made some enhancements as part of a junior academy project. I think I planted something...😀

[@AndreasSpiess]

Very good! It is best when students learn with things relevant for their life.

[@Snakke40]

@ 17:00 "[ ...] without oxygen the fire stops. Problem solved without collateral damage." As long as there are no humans in the same room. Else there will be a lot of collateral damage!

[@vincentnonnenmacher9352]

No that’s fine, because a good IT dwarf will send other people (e.g interns) to overlook the most important stuff (read servers, because some cost oriented people didn’t allow you a decent video stream of your puppies) and will monitor its health (obviously I’m talking about servers one). If humans probes eventually returns, everything is fine, it’s means your monitoring is validated by a secondary data flow (just document it). If not a review of your backup plan could be an consideration.

[@koma-k]

And that is why all such systems that I've seen use an inert mix of gases that are non-toxic (CO2 only would not be good). Some data centres use a reduced oxygen atmosphere (15-16%) which prevents fires from even starting, as the oxygen content is too low. Some people are more affected by this than others, getting more easily exhausted and getting a headache when working there, while others barely notice (luckily I'm in that last group).

[@SlykeThePhoxenix]

I think there's an evacuate alarm that goes off. Gives people a few minutes to get out. I also think it's not just pure CO2, but a mix of stuff, so any occupants would still pass out, but probably not die. Smoke inhalation/fire is probably going to kill them before the CO2 does anyway, but I'm no expert.

[@ramradhakrishnan9382]

HaHa, Back in the day when I worked on large IBM Mainframes, there were Automatic Halon Fire extinguishing systems which would rob the fire of oxygen. Needless to say it would be disastrous if you hung around! Yet, there were posted signs asking the operators to unload all tape drives, label them, then store them carefully in the fireproof and exit the computer room swiftly if possible.(!)

[@andrewpaterson5192]

It is shocking to see the difference in background CO2 in 6 years from 2018 to 2024. NIWA Baring Head in NZ is 421.5ppm today and Mauna Loa Hawaii is 427.5ppm. So it is likely that the new 2024 calibration point should be around 430ppm for the Northern Hemisphere and 420ppm for the Southern Hemisphere. Your video is , still, extremely helpful. Far more than any other on KZbin, even recently, related to these inexpensive IAQ sensors. My very cheap (

[@AndreasSpiess]

Interresting that the values are already so high! Thanks for the update. Concerning the eVOC sensors: As said, I was not very happy with them.

[@Os.-]

I have to say I like your presentations. A handy video, like most of yours are - I'll have to check out the Raspberry Pi series again! Thanks for doing these :)

[@AndreasSpiess]

You are welcome!

[@r1273m]

Bananas emit ethylene gas. This is why they can be picked before they are ripe and then ripened in stores that circulate the ethylene which helps the ripening process. My wife places unripe pears next to the bananas to help the pears to ripen. Bob

[@AndreasSpiess]

The son of my brother worked in a company where they ripe the bananas for Switzerland's biggest retailer (just in time). I did not believe it first ;-)

[@Leif_YT]

Perfect timing. I just hooked up my first MHZ19B 2-3 days ago. Sometimes i get massive co2 value drops that i can't really explain. Like in the middle of the night without opening a window or door. One drop could be the automatic 24h calibration, but the other ones confuse me a little bit. One problem could be that it's still on my breadboard powered by the 5V pin of a D1 Mini, another one could be that 2-3 days are just not enough time to be fully calibrated. But so far it does a much better job than the CCS811 eCO2 i tried a few months ago. Maybe those TVOC Sensors like the SGP30 / CCS811 could be useful for a hobby room with all kinds of gases / particles.

[@AriBenDavid]

I see this, too. I think it is variations in wind levels and directions, affecting the amount of outside air infiltrating the house.

[@AndreasSpiess]

I have now a ESP32 with different sensors reporting. I hope, that I will see a pattern after a few month. I disabled auto calibration to see what they really measure and only will enable it when I know that.

[@marcos.1767]

Great video. And more relevant than ever as right now in Germany we'll start to have a "venting" intiative at schools during Corona pandemic.

[@AndreasSpiess]

That is why I chose the timing. I had the topic on my table for the whole summer, but it did not catch my attention...

[@MichalKottman]

Nice coincidence, jist yesterday I started trying out a VOC sensor to make a "fart detector", planned be used to identify when our cat uses the toilet.

[@beware_the_moose]

solving life's problems, one cat fart detector at a time.

[@thebeststooge]

LOL.

[@shawnniedetzki7548]

I had just thought about this the other day for my cats as well, to determine which one and when they are deciding to not use their litter box.

[@chrislambe400]

Thanks dude, now getting cat food ads in the video.

[@dd0356]

maybe it will help decide better food for humans?

[@AnotherMaker]

I'm glad you used these higher quality sensors. The MQ-x sensors that come with the starter kits are relatively useless. I just finished taking 120,000 readings of my lab and your video has given me some great information of things I need to check. Thanks for all you do.

[@AndreasSpiess]

I will not include the MQxx sensors in my tests as they are made for different gases, I think. And my experiments with them were also not rewarding.

[@AnotherMaker]

@@AndreasSpiess Yes. The data sheets say some of them measure CO2 but the results were very unreliable.

[@neymarjr1292]

@@AndreasSpiess how about MQ-131 for VOC measuring and also which dust sensor should be used for this project additionally?

[@AndreasSpiess]

@@neymarjr1292 You can try. I do not know what they really measure... I never used dust sensors. only particulate matter sensors

[@arhitektche]

Do the same video for fine particles sensors

[@svrestless3425]

Just as easy as for other inspection. Either I2c or uart. There is also a lib for that in arduino ide

[@AndreasSpiess]

I cannot do this where I live. It would be very boring. The sensor would always show zero (i tried).

[@davesemmelink8964]

I have ordered a PMS5003 air particle sensor and will be trying this once it arrives. I originally wanted to get an SDS011, but I haven't found them locally. Does anyone know which is better? There is also one that does not use a fan, but I couldn't find it last time I looked - the fan will wear out eventually. Unlike Switzerland, South Africa has serious air quality issues in many places. We want to teach school kids about this. Many adults I know are completely unaware of this.

[@Ed19601]

I have been using the Winsen for some time already in a greenhouse. Very reliable

[@AndreasSpiess]

Thank you for your feedback!

[@AriBenDavid]

What levels do you get there?

[@Ed19601]

@@AriBenDavid high ones as I induce co2 in my greenhouse to promote growth, so it carries no relation to atmospheric co2 if that was yr interest

[@wilyartihoward2071]

You just read my mind! I just built one of these! With the MH Z19B.

[@AndreasSpiess]

Are you happy with it?

[@tonysfun]

Very nice again! I need to make mine soon, since my hobby rooms are all in the basement! Thank you again Andreas!

[@AndreasSpiess]

We "submariners" in the basements maybe are used to higher dosages. In a submarine the CO2 concentrations are at least 10 times higher than in fresh air!

[@tonysfun]

@@AndreasSpiess I did not know! I learn something new every day from you Andreas! Thank you very much! PS: Can't remember if I asked you also about my kit to make Tesla Coil. It is on my youtube channel: kzbin.info/aero/PLv52A7rm-UViZEOlzZfZOB9Gl8cjS3ze5 the very first, newest video. I don't like to hurt myself or someone else, but it would be nice to make this TC soon. So far no answers from anyone.

[@AndreasSpiess]

You have just doubled your number of subscribers ;-)

[@zyghom]

I deployed MHZ19B and it works like a charm with ESP32 It did not change my life but I am opening the window more often - bills for heating will go up during winter ;-) Btw after researching available sensors I am happy I decided to go for this one - it gives nice and stable readings - going to sleep with 400ppm and in the morning it is 1500 - hmm, now I understand why sometimes I wake up more tired than I went to sleep

[@AndreasSpiess]

Indeed, 1500ppm is a lot. So maybe a little more money for heating is a good thing!

[@zyghom]

@@AndreasSpiess I agree, however OSHA agencies provide "acceptable level < 5000 for long time work (8h or so)" - I believe it is way too high - I set up the alarm in my home assistant at 2000 ;-)

[@neilw2O]

Andreas! Nicely documented and explained.

[@AndreasSpiess]

Thank you!

[@tomgeorge3726]

Automotive O2 sensors will only work at high temperatures, not room temperature. Some O2 sensors have built in heaters or rely on the vehicle to heat the sensor as it warms up. The vehicle engine and ECU can run without the O2 sensor, this is called OPEN LOOP when cold. When the engine and O2 is heated, the ECU then runs using the O2 sensor reading, CLOSED LOOP operation.

[@AndreasSpiess]

I see. I did not know heat was a prerequisite. Thanks!

[@MaximumEfficiency]

do you have any data on o2 in different areas: forest, city, dessert, sea, cave, basement, apartment etc.?

[@ChriDDel]

The school of my son has a CO2 meter with colored LEDs in every classroom.

[@AndreasSpiess]

This seams to be an exemplary school!

[@erickcampos50]

Very nice! Where are you from?

[@ChriDDel]

@@erickcampos50 Northern Germany. It is indeed not normal for schools here.

[@hey-zq1vq]

@@ChriDDel Warum gibt es sowas bei uns nicht. Macht mit Corona ja noch mehr Sinn

[@forbiddenera]

@@ChriDDel doubt it's normal anywhere but it is fkn awesome!

[@Olavotemrazaodenovo]

Congratulations from Brazil. Here is the guy with brazilian accent.

[@AndreasSpiess]

Thank you!

[@Dimitriedmr]

As always Andreas does great videos.

[@AndreasSpiess]

Thank you!

[@TDG2654]

The reason lambda sensors are not used indoors, is because they need to be quite hot too work. Around 300 to 600°C hot. Inside the exhaust of an engine this is not too big an issue, but in open air it would take quite a bit of power

[@AndreasSpiess]

That is what I also thought because it works in the exhaust path. But I did not know it is mandatory. Thanks.!

[@albygnigni]

Hi Andreas! Do you know the CCS811 VOC sensor? It's the most popular on AliExpress. I've been using it for a while and it is pretty accurate. By the way I have a question, do the sensors you showed need a burn-in for accuracy? Hot plate ones often need a 48hr burn in

[@AndreasSpiess]

The CO2 sensors do not need burn-in. And I mounted now a CC811 with the other sensors for comparison.

[@myounges]

@@AndreasSpiess how did that comparison go?

[@ramradhakrishnan9382]

Andreas, Thank you performing the tests that I would otherwise have had to perform myself! By the way, if you want an excellent supply of CO2, you could try Dry Ice, which is nothing but frozen CO2. I believe you can get it from grocery stores, or perhaps from ice cream suppliers. Stay safe!

[@AndreasSpiess]

Thank you for the tip!

[@jub8891]

i have a sharp air purifier that triggers the fan whenever i fart. it also gets triggered by alcohol fumes, like in anti-bacterial hand wash. it must be almost 10 years old now but the sensor is still very sensitive to changes in the air

[@SlykeThePhoxenix]

A fart controlled fan! My gf would love to get me one for Christmas!

[@LawpickingLocksmith]

I have a 20 year old split air-conditioner made in Japan and still goes like new. Buy Chinese made and keep replacing.

[@coffeecuppepsi]

one fart to turn fan on, two farts turns it off?

[@369ranch]

I am back in school later in life and I agree that we need sensors in each classroom. I always thought there was a reason such as this that you get exhausted after 50 minutes in a class.

[@AndreasSpiess]

Maybe this is the reason, maybe it needs some time to get used to the school situation again ;-)

[@bobapthorpe]

This is similar to my first ESP32 project, an atmospheric monitor/logger that measured particulate and combustible gas concentration with a Shinyei PPD42NS and an MQ-2 sensor. It uses GPS for a reference time signal and a BME280 sensor for reference pressure, temperature, and humidity values. I looked into MQTT communications but got distracted by trying to estimate power requirements (was hoping to add solar panels and battery). The particulate sensor uses a resistor as a heating element to move air and particles past the IR sensor and I believe that dominated the power consumption. Search for apthorpe/aerosniff on BitBucket for the code and Fritzing schematic & circuit diagram if you're interested. Thanks for making ESP32 development so accessible; I wouldn't have been able to do that project without your videos :)

[@AndreasSpiess]

You seem to be quite experienced with sensors...

[@foxabilo]

You are a genius sir, that is a fantastic idea!

[@AndreasSpiess]

Thank you!

[@MichaRutkowskiEngineering]

Great material! It is a good thing to always seat in front row

[@AndreasSpiess]

Thank you!

[@dimonmontana]

You absolutely forgot about the ccs811. It's really cool and chip sensor with low power mode.

[@AndreasSpiess]

Looking at its datasheet it is very similar to the one I used. I would expect the same issues.

[@gnom69]

Great video! I would be very interested if you can measure co2 or voc (or air particles?) increase while running your 3d printer. Especially PLA/PETG/ABS which we home-makers can use. Anectdotally I‘ve sometimes felt the „meeting effect“ in the beginning when I had the printer stationed in my bedroom.

[@AndreasSpiess]

I would not expect any increase in CO2. Maybe VOCs are emitted. I will see it in the future...

[@thenickdude]

@@AndreasSpiess Printing ABS should generate styrene gas which is a VOC - it'd be really interesting to measure the impact of this at various distances from the printer.

[@avatarteamultra]

Nice coincidence There was a "zukunftstag" at ETH Zurich two weeks ago. We have built CO2 measuring boxes with kids. At the end they could take them home and place them in their classroom now they know when to let some fresh air in.

[@AndreasSpiess]

Good idea from my Alma Mater... Which sensor did you use?

[@avatarteamultra]

@@AndreasSpiess a MQ135

[@AndreasSpiess]

Not a good choice for CO2, I think. But maybe the price was important...

[@foxabilo]

After a long weekend of drinking, I have many toxic gasses in my apartment.

[@AndreasSpiess]

:-))

[@viniciusnoyoutube]

Another fantastic project and video! Thanks!

[@AndreasSpiess]

You are welcome!

[@bryanst.martin7134]

@17:21 your breath is lethal! ;-) This is a good reason for such a device. In my experience teachers can be extremely boring, and having a poor environment for your brain doesn't help.

[@bryanst.martin7134]

So if you perform CPR, are you committing attempted murder? How about we conjure up a CPR respirator that doesn't give CO2 to the victim?

[@AndreasSpiess]

In many situations people use air several times (if you hyperventilate, for example). Oxigen is not used up by only one time breathing.

[@svivs]

Thanks for the informative video, just what I needed right now. :-) I’m working on a MQ135 VOC sensor and Sharp infrared dust sensor project. The MQ135 fluctuates a bit in it’s output values so I guess it’s best for short term relative measurements. My program periodically adjusts the “zero” value to compensate.

[@AndreasSpiess]

It always depends on which gases you are interested in. The problem of calibration is the assumption that you know when the values are lowest and how much lowest is. To determine that, you need a proper sensor. Otherwise all is only guesswork...

[@Rouverius]

I think the major problem with lambda sensors is the high operating temperature required (300° to 600° C). I've been in pretty hot meeting rooms before but even this is a bit much.

[@A38-d7y]

I think this is also because the exhaust oxygen varies a lot (0-20%), where as humans don't consume nearly as much and change is harder to detect

[@wsy2304]

Great video and look forward to the update particularly how the eCO2 correlate with CO2 readings on extended runs. I currently use a CCS811 for eCO2 and plan to test the SGP30 for similar reasons. Also not sure if I missed but did you send humidity compensation values into the SGP30? Per the datasheet this affects both eCO2 and tVOC reading

[@AndreasSpiess]

I did not enter the compensation values. The TVOC sensors are anyway showing completely different values as the CO2 sensors :-(

[@grindel80]

hahah i have to laught everytime is see the little hand :D (+1 for the cat)

[@AndreasSpiess]

It is a good way to show small things...

[@markj3851]

Thanks for the great video Andreas. Any idea how "exposed" the sensor needs to be to read accurately? I'd like to add one to my camper which is a small enclosed space, but I'd likely put it in a small project box in a cabinet or out of site location. Would you think the detector would be useful if it's not out in the open, especially since you mentioned CO2 drops down below air?

[@BerndFelsche]

CO2 levels in outdoor air vary considerably over the day and between seasons. They also vary substantially between locations, even at the same altitude. Using a global average is like using the average of telephone numbers to call somebody. CO2 gas presence is a sign of life... Essential for the carbon cycle that sustains our lives. When CO2 levels decline below about 180ppm, plant life struggles. You could hike up to the treeline on a nearby mountain and calibrate your sensor to a baseline of about 200ppm during daylight hours. CO2 levels can be higher at night due to decomposition of biomass and a slight increase in air pressure... But without sunlight, the higher CO2 is of no use to plants. Exhaled breath contains about 40000ppm ... sometimes higher. If your readings are substantially lower then it's likely that the sensor is wrong. P.S. drowsiness at University lectures was more closely correlated to the acoustic emissions at the front of the theatre than ambient CO2 levels 😀

[@AndreasSpiess]

Do you know how much the CO2 level differs from place to place. I did not find such information. I assume it is only a few PPM

[@BerndFelsche]

Nearby, well flushed locations are within about 5ppm. See e.g www.mdpi.com/2073-4433/9/10/367 Globally, variations are wider... IIRC 20ppm variation at sea level between the tropics and temperate regions of the Atlantic, at the same time of day. That was by measurements taken during the 1920's. Proper calibration is only by calibration gas mixtures.

[@AndreasSpiess]

I also found info here: www.esrl.noaa.gov/gmd/ccgg/trends/monthly.html For our sensors these variations are below measuring errors.

[@CarlOlovGustav]

True, but relying on the ABC algorithm started by Senseair in early 90ties tracks and keeps in sensor memory only the lowest such outdoor reading, which is very easy then to correlate to the atmospheric baseline. Temporary local emissions and peaks and other variance over the day/week are don't care. Seasonal variance (green plants in summer vs. autumn and winter bio decay) still apply if there's no added intelligence, but that's not a very big impact to atmospheric baseline and NDIR sensor accuracy. The true strength of ABC is however that any faulty drift offset over the lifetime (15+ years) is naturally delimited to the continuous effective sampling of the atmospheric baseline, so it never spirals out of control compared to dual-channel NDIR sensors that rely on internal reference signal ratios that is "assumed" pristine forever but typically only lasts a few years.

[@MaximumEfficiency]

also higher CO2 levels help plants grow faster (and absorb more carbon as a building block)! btw do you have any data on o2 in different areas: forest, city, dessert, sea, cave, basement, apartment etc.?

[@electronic7979]

Very good and helpful video 👍

[@AndreasSpiess]

Thank you!

[@juweinert]

A thing to keep in mind. If it's only about how people feel, measuring CO2 is is right way. Higher CO2 concentrations are what makes us feel bad. But it's not a good indication on wether or not the environment is suitable for you, or healthy. That's a "fun" thing about humans. We indicate if we are suffocating from oxygen depletion by measuring CO2 concentration. You can easily suffocate without noticing if the oxygen get's replaced by something different than carbon dioxide

[@Xgy33]

You are a legend professor!

[@AndreasSpiess]

:-)

[@thesimbon]

Please do a comparison with CO sensors too and possibly PM/dust sensors

[@AndreasSpiess]

I am not sure if PM sensors are needed inside. I had one outside and it was boring. Too clean air :-)

[@thesimbon]

@@AndreasSpiess because you don't live in the center of Milan 😅

[@pioupiou3935]

Always very interesting video, thank you very much !

[@AndreasSpiess]

You are welcome!

[@arifindobson]

As always amazing video master Andreas. I think I will try it in my university classroom, because boy in Physics class we are always tired, I am 100% sure it is not because of the boring subjects but because of the high CO2 concentration. I am curious to try multiple VOC sensor, I will try with the bosch BME680 and SGP30, because CO2 is still above my maker budget. Again thanks for the amazing video!

[@AndreasSpiess]

I did not find out what the BME680 really measures...

[@arifindobson]

@@AndreasSpiess it measures Temperature, Humidity, Atmospheric Pressure and VOC. Made by BOSCH, I assume it will be good 😁

[@일한-f3z]

it's really goooood video. Is it ok for output cycle faster and , how to check the fastest rate? i want to see more detail graph

[@AndreasSpiess]

This is an old video. So I do not remember the details :-(

[@dukenukem3568]

Heads up for Raspberry Pi users concerning the SCD30 as it mentions I2C Clock Stretching in its documentation which could be a problem for Raspberry Pi users who want to use the SCD30 I2C interface, so you might have to use one of the other SCD30 interfaces with a Pi. Andreas perhaps a good video topic would be I2C clock stretching and the Raspberry Pi.

[@AndreasSpiess]

I think it would be too "special". Most people would not know what it means or what it is for.

[@grantaylward7125]

Great project, I am also using an SGP30 to measure eCO2. Your values are much smoother than mine. I think my calibration did not go as well- I simply let it run for 12 hours which is what I thought the documentation outlined. What calibration steps did you take to get this good data output?

[@AndreasSpiess]

I average the values.

[@landstreicher9726]

A nox sensor would be useful to detect the dirty air in cities. Especially in the cold season, there are inversion weather conditions. Poison gases accumulate on the ground, so that it stinks terrible, so you better keep the window closed. Btw. LPG does not release nox and costs less than half its consumption.

[@AndreasSpiess]

This video was about inside air. I once measured our outside air. It was very boring where I live...

[@m.luthfi.alhadi]

*me read the title, "How to measure the VOC with arduino" S P I C E per Colony ? by the way, great video sir!

[@AndreasSpiess]

Thank you!

[@charleyfan1908]

Hydrofluorocarbon is used for fire suppression in most data centres. The gas cylinders are smaller compared to CO2, and safer for people to return.

[@AndreasSpiess]

Thank you for the additional information!

[@nektarioskourakis8331]

Great job as always !!! thanks! Can you recommend a specific sensor-not too expensive- to study photosynthesis? If i get it wright eCO2 sensors are excluded.

[@AndreasSpiess]

Yes, you need "real" CO2 sensors if you need to measure Co2. The Sensirion sensors and the Chinese ones were good.

[@thealbion3946]

Great video Andreas! I was just wondering, you mentioned that the CO2 sensors could not be switched off. Is this because the sensors take a while to start reporting accurate co2 data? If not, could you explain a bit more…I’m thinking of a scenario where you could have a battery powered esp32 chip connected to the sensors and putting it to sleep after collecting data to conserve battery…would this work?

[@AndreasSpiess]

Yes, the sensors heat up and therefore need quite some energy. Consult the respective datasheet if you want to know how much. Then you can do your calculation on the needed battery size.

[@nashaut7635]

Exactly what I was looking for! Thanks!

[@AndreasSpiess]

You are welcome!

[@tommihommi1]

wow, that chinese CO2 sensor finally is an affordable CO2 sensor. I've been waiting for something like that for ages.

[@efimovv]

Because of this sensor I open world of ESPs and other controllers... But be careful with them - there are 2 versions, and as I understand manual calibration of first one (without B) may "destroy" device - as it need 0 CO2 to calibrate. Second one use more reliable strategy to auto-calibrate and manual calibration assume to 400ppm baseline. And, I have no idea how they differ if you have them in hands...

[@ChrisPrefect]

Leider schaffe ich es nicht das MH-Z19 Arduino-Sketch zu kompilieren. Ich habe das Modul "FreeRTOS" installiert, aber Arduino meldet trotzdem "MH-Z19:11:31: error: freertos/FreeRTOS.h: No such file or directory". Wie wurde der Sensor an den ESP8266 angeschlossen? Merci!

[@AndreasSpiess]

Dieser Sketch läuft nur auf einem ESP32, weil ich den Sensor an Serial2 angeschlossen habe. Sonst musst du Softserial verwenden.

[@Ownedyou]

Is that a Surface tablet? They seem to be cool but pricey... Is it worth it?

[@AndreasSpiess]

This is my business laptop. For me it is ok. Small and light.

[@DougHanchard]

This episode should be a high school homework assignment.

[@AndreasSpiess]

Maybe some of my viewers are teachers?

[@nashaut7635]

@@AndreasSpiess I know one who is and I'll suggest him :)

[@Snofperiment]

Yes am a biology teacher at high school in Netherlands. And I love iot. See my comment above. Would be fun to build!

[@Parapascal]

This topic is on the agenda now! I will build one for my school. Which sensor should I buy now?

[@AndreasSpiess]

For shure a true CO2 sensor. The others do not display real CO2 values.

[@Parapascal]

@@AndreasSpiessPrima, danke. Habe einen MH-Z19 zum testen gekauft. Werde ihn wohl nicht mit Batterien betreiben können. Aber ich plane ihn in mein bestehendes influxdb/grafana Setup per lora einzubinden. Was denkst du über die Montagehöhe des Sensors. Am besten auf Kopfhöhe der Schüler oder?

[@AndreasSpiess]

Die Höhe must du probieren. Soviel ich weiss ist Co2 schwerer als "Luft".

[@rachelkim-sue5874]

Great analysis. Do you know of any CO2 or eCO2 sensors that are suitable for battery operation?

[@AndreasSpiess]

No. The principle always uses around 100mA.

[@GaddStuff]

Hi Andreas, Thank you for sharing this. I see you are serious about this. Maybe I can ask your advice on my CO2 issue? If you don’t reply than I guess I can’t 😊. I’ll try to be as short as possible. Outside in my garden I have a storage which only has a door, no ventilation grille. Why not? I tried to prevent sound leaks for my drumming. First I applied isolation material and than build up my drumcabin in my storage (box in box idea). My drumcabin has a ventilation panel on top who moves dirty air from the inside of my drumcabin to the outside of my drumcabin through a bathroom ventilator. But … that dirty air can’t leave my storage itself. So out of safety I bought a good CO2 detector € 145,-) who’s used in schools etc. but after about 45 minutes it’s display turns into red (1200 ppm and higher). It’s very annoying that I have to ventilate by opening the door between drumming. The space between the storage door and my drumcabine is about 75 cm in depth x 220cm in width and 225 cm in height. A company adviced me a Decentralized heat recovery EcoComfort 2.0 Smart which standard doesn’t have a CO2 detector but that’s an option and maybe I can connect my own CO2 detector to it. What the EcoComfort 2.0 Smart has is a VOC sensor and I read in an article that a VOC sensor does practically the same as an CO2 sensor (and maybe better than a CO2 sensor): automatically let dirty air out and fresh air in. What would be your advice? Many thanks in front.

[@AndreasSpiess]

As said in the video: If you are concerned about CO2 the VVOC sensor will not do the job. However, I would take some measurements with both to see if their values are related in your situation. If so, the VOC sensor is a good replacement.

[@drumcoachjack3507]

@@AndreasSpiessthank you.

[@Snofperiment]

@andreas spiess I am a biology teacher. And yes air quality is important for staying focused. Would be interesting to build with students. I prefer blynk platform to read data since students can easily work with that. I already have nodemcu + supplies, just need to order the sensor.

[@AndreasSpiess]

many streets lead to Rome as we say here ;-) Good luck!

[@Snofperiment]

Dear Andreas, thanks. I've been to Rome already. Assisting you in a project would be much more fun;)

[@brainfornothing]

Very interesting. Thanks for sharing !

[@AndreasSpiess]

You are welcome!

[@davesemmelink8964]

I bought a set of 9 cheap gas sensors a while back but just got around to trying them now. It was my first ESP32 project using more than one ADC input, so I was very surprised and disappointed to find out that if you use WiFi on the ESP32, half the ADC inputs are disabled, and in the case of my DOIT ESP32 DEVKIT V1's, the ADC pins labelled VN and VP also don't work, so I was left with 4 usable ADC pins. I'm considering disabling WiFi, and using Serial Comms to get an ESP32 to use an ESSP8266 to do the WiFi comms to my Node.Red server. Or I could just use 2 ESP32's to handle 8 sensors.

[@AndreasSpiess]

Or you add an ADS1118 board or another extrernal ADC

[@___Q-bot]

16:30 could you use a can of soft drink or sparkling water to obtain the CO2?

[@AndreasSpiess]

This should be possible.

[@garyseaman6105]

Great video thank you. If i wanted to monitor air quality in my living room with a log burner, would these sensors work please?

[@AndreasSpiess]

These sensors do what I described. You have to decide if you are interested in the values they provide.

[@kickthejetengine]

As a result of this video I actually built a project that would be doable by students. It uses the MHZ19. I've just finished the firmware and everything works fine. Only very minor soldering is required. How would I get in contact with Andreas about this? 15:40 he talks about this.

[@AndreasSpiess]

You can contact me on Facebook messenger, or on Twitter.

[@kickthejetengine]

@@AndreasSpiess Thanks for responding! I've sent you a Facebook Message with the details of my build!

[@avejst]

Impressive review/update Thanks for sharing👍😀

[@AndreasSpiess]

Thank you!

[@robertasmaleckas8424]

I've been curious to try indoor CO2 monitoring for a while and was not aware of the SCD30 - seems to be a great little device! There's one thing I find slightly unclear - it's datasheet lists a maximum I2C line voltage of 3V and insists on level shifters for higher voltages, while both chips you have listed in the description (ESP32 and ESP8266) operate at 3.3V on I2C according to Google. Is that a small enough gap to not have any significant risks or did you use some kind of level shifter/voltage divider? I'm thinking of trying to run this off of a Raspberry Pi's I2C (3.3V), but am a bit concerned not to fry the sensor - could you share any insights on this?

[@AndreasSpiess]

I did not see these 3 volts in the data sheets I looked at. It works here with an ESP32

[@tobiasheeb9721]

I'm a big fan from east switzerland. I just bought a sensirion scd30 and would like to battery operate it. I planed to frequently switch them on with a TPL5110 Nano Power Timer to measure at an interval of 1 min, send the result to an mqtt server and then power off for the next minute. Do you have any suggestion why this could be a bad idea?

[@AndreasSpiess]

Look how long it has to run till it gets good results... If I remember right they need some time to stabilize.

[@fibranijevidra]

Very informative and interesting video. Thank you!

[@AndreasSpiess]

Glad you enjoyed it!

[@LarsBudek]

Is it possible to measure outdoor pollution, for example, traffic pollution in a crowded area? Which sensors could be interesting to use in an ESP32 / LORA project. Thanks for great videos. Being inspired and having fun with them when Sunday's breakfast is enjoyed

[@carstenbrinkschulte3231]

I think the problem is that these sensors are specified to be used for indoor applications and the data sheets state that explicitly. With operating and storage temps between 5-50 degree Celsius and negative impacts of high levels of humidity on sensor performance these sensors probably won't last long in harsh outdoor environments. Let me know if you find a good sensor with support for CO2, hydrogen that works in outdoor conditions, is affordable and works at low ppm concentrations.

[@AndreasSpiess]

You find many particular matters sensors using ESP32 online. They are made for outside air. Most of the outside gases are probably not easy to detect and need more expensive sensors.

[@haajee1]

And the CCS811? The should correct the measurement also with humidity to be more accurate? Btw ESP Easy has support for the Senseair sensor :)

[@AndreasSpiess]

I just connected a CC811 for comparison...

[@cervezatoledo9634]

Hi how are you?, thank you for the video, i was wondering if there could be any diference in the values that you get using the mh z19 sensor rather than the Mg811 co2 sensor?, or which could be the differece?, i appreciate your help, thanks a lot, best regards

[@AndreasSpiess]

Maybe you watch my update video?

[@cervezatoledo9634]

@@AndreasSpiess hola andreas, muchas gracias por tu respuesta, te agradezco tu tiempo, oye disculpa, no entendi, te refieres a un video nuevo?, tienes otro?

[@AndreasSpiess]

Yes, the CO2 cuckoo video

[@cervezatoledo9634]

@@AndreasSpiess thank you very much andreas, thank you for you time, take care

[@beware_the_moose]

I'd like to see one on the PMS5003 if you feel like doing it, it's a really solid PM2.5 sensor

[@AndreasSpiess]

Particular Matter sensors have been covered elsewhere and are (hopefully) more a problem of the outside air in crowded areas. Where I live it was boring. Nothing to see...

[@beware_the_moose]

@@AndreasSpiess I live on a main road; cooking causes most of the pollution in our house even still. I was surprised! The other thing, most people out there on KZbin are using a particle sensor that doesn't work..the Sharp brand one and equivalents. It's not designed for this job and reads out garbage, but they all use the same code! And it puts out nonsense! The code doesn't work at all. So it's a more interesting topic than it may appear.

[@kevinwalters5160]

@@beware_the_moose Cooking is a big surprise, my PMS5003 goes nuts if I fry bacon and it's not even in the same room. I'm about to get a Sensirion SPS-30 which may give better output for PM2.5/PM10 than Plantower's.

[@hanskobischraaner6551]

I am an absolut Beginner in electronics. I have to implement a MiCS-2714 or something similar in our weather-sensor. So i searched for it on KZbin and found you. It's funny, that we live not even 10km apart. Now I have a huge problem with the Sensor. I do not have your Cat for the calibration process. Could you please tell her to come over, cause I'm pretty lost with this topic. Sensors and I2C ADCs and so on, not my world.

[@AndreasSpiess]

:-)) I usually try to cut the problem into its part and solve one problem after the other: Micro, ADC, sensor. Like that I have less "moving parts". Or you buy an I2C sensor which has the ADC built-in. That is my preferred way...

[@steliosstamatakis844]

Can you please test also Scd41 sensor and exploriR-M sensor in humidity environment ?It is a good test..

[@AndreasSpiess]

The Scd41 works well and according to the datasheet. You can trust Sensirion ;-)

[@patyescorcia7013]

hi Andreas! I am using the SCD30 sensor for a project, but I need to use 18 of them. Do I need a mutiplexer? Or how to separate the signals from each sensor, if I know that by fabrication it has an address Ox61. Thanks!!

[@AndreasSpiess]

You need I2C multiplexers if the chip only offers one or two address

[@jpcv88]

Hi Andreas , how will you go in to wiring the barometer , I am trying to develop a multi air sensor based on your video

[@AndreasSpiess]

Google knows ;-)

[@jpcv88]

@@AndreasSpiess thanks it did know, now I am trying to set the altitude within the scd30

[@maxmund1047]

The Lambda sensor actually compares the oxigen levels between the exhaust and the outside

[@AndreasSpiess]

Thank you for the info!

[@MalagasOnFire]

Nice video. One project would be to build a project for detecting carbon monoxide for living rooms , near fireplaces, gas heaters, etc to prevent its toxicity, using VOC and ESP32, and trigger alarm(s)

[@ristomatti]

For this purpose I'd suggest buying a carbon monoxide alarm. Those can be often found from the same shelves as fire alarms.

[@AndreasSpiess]

What kind of sensors do they use?

[@MalagasOnFire]

@@AndreasSpiess I have a question.. Does the VOC sensor is suitable for the carbon monoxide detection? In the video the datasheet or table show CO with a wide range 1 - 1000ppm at 11:30. The idea is to log the data onto web and mass storage device using ESP32 and VOC sensor and implement the alarms

[@MalagasOnFire]

@@ristomatti Do they offer the datalog option to web / mass storage device?

[@ristomatti]

@@AndreasSpiess I don't have any idea actually. They are quite expensive compared to a fire alarm and seem to expire relatively quickly. The price/value ratio is not good enough for my use case where the fireplace is used seldomly and only during some months of the year. I might think differently if I'd have children around.

[@zumi002]

Hi Andreas! The high pitched noise is gone from your voice-overs! Either I got sufficiently old, or you did something with the recording. Just wanted to report back, thanks! I will comment separately about my experience with CO2 sensors to not mix things up.

[@AndreasSpiess]

Thank you for the feedback. I changed the microphone and the ADC.

[@zumi002]

@@AndreasSpiess This really improved the enjoyment of your video for me, I appreciate it a lot that you looked into it. Thank you! :)

[@FOATE]

If you're using automatic calibration on the MHZ19B sensor, does it matter that I am using it in a high CO2 environment where CO2 does not drop below 800 generally?

[@AndreasSpiess]

I think: Yes. Because it assumes the lowest level at around 400ppm

[@FOATE]

​@@AndreasSpiess Thx for confirming my suspicion. I am planning to use the sensor in a greenhouse so ambient CO2 levels will never go below 600 at all. The soil will provide plenty CO2 gas around the clock to ensure that. I think I already found a solution, there's a library on github by WifWaf that allows a beginner like me to easily disable automatic calibration and do it manually :)

[@ggonmar]

Any comment on the MQ-135 sensor? It does seem to measure a bunch of things, CO2 among them, for a price on the dollar.... but I doubt it uses the method you describe... thoughts? Thanks!

[@AndreasSpiess]

I do not think it measures CO2, only eCO2

[@ggonmar]

@@AndreasSpiess eCO2?

[@AndreasSpiess]

I think I explained it in the video.

[@thedanyesful]

Couldn't you calibrate by spraying some nitrogen across the sensor for a few minutes until it reads 0ppm?

[@AndreasSpiess]

I do not know. "Calibrating" it with the outside air is ok for me.

[@FilipeNeto616]

Can the VOC sensors be used to measure toilet "activity" and trigger a venting fan? You can guess on what I'm thinking about, right?

[@AndreasSpiess]

I assume, yes. But I do not know. Maybe google knows?

[@naimfuad5913]

dear andreas, you mentioned altitude effect the reading for gasses. 1 sensor caught my attention by Bosch's BME680 where not only it measure voc but also humidity, pressure and temperature. I hope you can review this sensor and get your opinion on this.

[@efimovv]

This sensor rely on closed source lib to extract meaningful values. Thithout it, it show some "resistance" which is non-linear and not very useful.

[@naimfuad5913]

@@efimovv cool, but correct me if im wrong i thought that library was only for calibration and stuffs

[@efimovv]

@@naimfuad5913 nope, it for interpretation of "gas resistance" value to something more useful.

[@piotrkuranty8512]

I've been waiting for such an episode from you. I recently built a sensor on the SGP30 sensor but I am not entirely satisfied with its operation. How long have you tested your GSP30 sensor? A very interesting episode :-)

[@AndreasSpiess]

I used it only for a few days.

[@piotrkuranty8512]

@@AndreasSpiess My SGP30 after a few hours of work shows very inflated values. These are certainly not real measurements. You don't know what could be the reason?

[@AndreasSpiess]

I just wired a few sensors together and plan to monitor the differences over the next few months