Ah, I was unaware that the SmartAir Qingping Pro 2 Air Quality Monitor was actually just a fancy name for the Qingping Air Quality Monitor Lite. Definitely not looking to get that one!
“On the topic of Qingping, I’ve already reached out to them regarding adding a customisable baseline adjustment period. They’ve received the request and said they would pass it on to the development team. Unfortunately, I don’t know if it is something that will be added, but I really hope so!”
That’s very kind of you!
I’m unsure on whether I should wait to see whether that materialises into something (and if so, how long I should wait), or whether it would be better to rule that out as an option for now (since even if they did immediately make that change - which is unlikely, since changes usually take at least a little time - there will still need to be a period of testing to see if whatever change they make works and allows for accurate test results)?
If not, it sounds like the AirGradient ONE is going to be the best option for me, based on what is available right now.
Thanks for answering that question re: platform access. Approx $24 a year (I’m assuming that’s US dollars, so that would be $38 for me) is not prohibitively expensive, so I don’t mind paying something like that after the initial ‘included’ period has ended.
I recently bought a dresser, which is in my bedroom, and I am concerned about off-gassing. I read that the process can take months or years, and I’d like to be able to use the dresser and breathe the air around it before then. I painted the inside with shellac, based on some online advice, but I have no idea if that is actually effective.
Is there an air quality monitor that could help me determine if it is off-gassing (I read about formaldehyde and I imagine there are other problematic chemicals) to a concerning degree?
I am a little confused about how the VOC sensors are calibrated. You said it is set by the manufacturer, but also that the baseline can be influenced by whatever the current air quality is, assuming that VOC levels are stable.
Either way, since I am mainly concerned about VOCs in the bedroom, would I be able to get meaningful information by comparing the readings in the living room to the readings in the bedroom?
Thanks for your help and all the info you provide.
I agree - it’s hard to tell when or if they will make this change, and it could take a while. I’ve followed up again today to see if it’s something that is even possible and to hopefully get a timeline on it if so, but I think the AirGradient ONE might be a better choice for the moment.
The thought behind the pricing was to make it reasonable and to only charge for features that cost AirGradient (as we have to pay for server resources). No one wants to pay a subscription, but I think they’ve made the pricing quite fair.
With that said, unless you want alarms I don’t think the premium subscription is needed. I’m unsure how much historical data will be able to be kept on the free plan, but it should still be at least a week or two (I wish it were one month, though!).
VOC sensors are typically calibrated with ethanol at the factory (by the manufacturer). This calibration ensures they are quite accurate for ethanol and recognise ethanol in parts per billion (ppb) with good accuracy. Since there are so many VOCs, these sensors can’t be calibrated to every compound, and ethanol is the chosen VOC.
This means that, in theory, if there were 10ppb of ethanol in the air sampled by the monitor, it could give an absolute output of 10ppb - an accurate and useful result. Unfortunately, if it comes up against another compound - let’s say formaldehyde - there might be a concentration of 10ppb in reality, but since the sensor is less sensitive to it (and calibrated based on ethanol), it might read significantly lower than 10ppb.
On top of this, the sensor can’t differentiate between VOCs, so there’s no way to know exactly what that 10ppb consists of. The below image illustrates this very well (MOX = metal oxide sensor, the type of sensor commonly used to measure VOCs). As you can see, the sensor detects 1:1 for ethanol but is less sensitive to formaldehyde and much less sensitive to toluene.
This ethanol calibration is done at the factory by manufacturers.
Unfortunately, since VOCs are so difficult to measure, most sensors use a relative index instead of giving absolute values, which would be entirely incorrect anyway. This baseline is constantly adjusting, and this is the ‘calibration’ that the monitor is constantly doing in the background as you use it. It’s quite difficult to explain, but I hope this helps a little.
Yes, I agree with @SeekingCleanAir’s thoughts. You could do a comparison, but you would need to do it in such a way that you can actually identify the peaks in the bedroom. I would recommend putting the device in your living room for 24+ hours to establish a baseline before moving the device to your bedroom for a few hours. If the levels climb, you know the bedroom has more VOCs than the living room. After a few hours, I would move it back to the living room so the device can keep the air in the living room as the baseline.
If you wanted to see how good the air in the living room is, you could do the same procedure but leave the device next to an open window for 24 hours to get an ‘ambient’ baseline before moving it to your living room for a few hours to compare levels.
The key here is really just to not leave the monitor in the room your testing for extended periods of time, as the baseline will begin to adjust and after 12/24 hours, it will consider the air around it as the baseline.
Sorry for the late reply - the website wouldn’t allow me to send any more replies (apparently new users are limited to 3 replies on any one topic. I guess that’s a spam filter thing?).
“The thought behind the pricing was to make it reasonable and to only charge for features that cost AirGradient (as we have to pay for server resources). No one wants to pay a subscription, but I think they’ve made the pricing quite fair.”
I definitely agree the prices are fair. I pay a fee for a domain name and website hosting for my blog, so understand that it’s not free for AirGradient to provide the website and the many functions of the dashboard. I’m grateful that they’ve kept the subscription price affordable.
Sounds like the AirGradient ONE is the ‘one’ for me, haha. I’ll purchase today, using the affiliate link on your website.
Order made! I’ll be eagerly tracking it and hoping it arrives here asap! (But being in a small country town, on a different continent, I’m totally aware that it will likely take some time. I know that’s not AirGradient’s fault!)
Oh, thank you for letting me know - I will look into that. Unfortunately, I’ve suddenly had a lot of spam problems, so I had to tighten a lot of the anti-spam measures.
Awesome! Please feel free to reach out at any time if you have any questions. If you reach out to AirGradient support, you will likely get me anyway, haha. I’m always happy to accommodate questions (and even other things like your findings) here, too - I also think a lot of them help the community as it’s more likely than not that others have the same questions.
Hello, new user here… great website, reviews and info!
I’ve read this entire thread and your various other links about the issues with affordable TVOC sensors, so have a pretty good understanding now. Having said that, I’m considering the AirGradient ONE and curious can it switch between a TVOC index reading and absolute reading? I know you mentioned the QingPing AQM Gen2 can do this. I’d like the ability to toggle between the two, for cases where I simply want to see an absolute reading that is not being auto calibrated (even if it’s not accurate due to the unknown mixture of VOCs in the air).
Yes, on the AirGradient ONE, you can switch between ‘absolute’ and relative as long as you know that the ‘absolute’ reading is quite flawed (which you seem very aware of!). The screenshot below shows my AirGradient dashboard, where I’ve enabled the ind30 (absolute in parts per billion) and ind40 (relative 0-500 index) readings.
@Ethan I appreciate this site and wanted to reach out in this thread to try and get some clarity on how the Qingping Air Monitor 2 uses the VOC index data from the Sensirion chip. My understanding from Sensirion is that they compare current data to an index value from the previous 24hrs. If current data exceeds that index value it is reported as a number above 100. If current data is below that index value it is reported as a number below 100. Is this the number that the Qingping monitor outputs? Or are they doing something else with those data? Their explanation of eTVOC in the app puts everything above 37 and below 120 as ‘slightly high.’ This doesn’t make sense if it is reporting the index value directly from the Sensirion chip. A reading of 100 should indicate no change from the index value of the previous 24hrs and a reading of 120 should indicate a minimal increase. But Qingping calls a reading of 120 a ‘high’ reading. This doesn’t make sense to me unless they are doing something else with the data and have their own proprietary index scale that is distinct from Sensirions. Thoughts?
Hi! Great question, and something that I overlooked.
I’ve reached out to Qingping on this matter as I think that would be the easiest way to get a conclusive answer. I will get back to you as soon as I hear from them!
The method of obtaining the VOC index readings by Qingping air monitor 2 is the same as Sensirion, but the evaluation method is different.
Since the Qingping Air Monitor 2 allows the VOC readings to be switched to mg/㎥ or ppb, we have a specific evaluation standard for mg/㎥ and ppb, which aligns with this scale.
Wonderful thread, thank you for taking the time to lay it all out and being so responsive with your replies.
I live in LA and am looking for the right tools to help me make informed decisions re: the risks from post-fire air and water quality. I’m worried about VOCs in particular, looking for a monitor to help me determine when I need to upgrade my KN95 mask to my kitted respirator bc gas/chem levels are too high.
1. Which air monitor would you recommend for home? reading previous comments, I’m leaning towards AirGradient ONE because of the adjustable VOC baseline calibration period. But having an app, that would give me real time notifications would be helpful (ADHD here lol)
2. Are there any good /affordable options for portable monitors?
3. Any tips for establishing the baseline when outside is probably already rather toxic?
I’m not directly in a fire zone, but I figure all of LA is experiencing the fallout from these urban fires and AQI alone doesn’t cut it.
Thanks @Ethan. While informative, I’m still struggling a bit to understand what this really means. My understanding from this site and others is that this type of TVOC sensor is useless for understanding absolute values. Sensirion themselves confirms this for the specific sensor used here - hence the index. It seems confusing for Qingping to convert the sensor output to an absolute value. How does this ultimately take into account the index from the past 24hrs? Does ‘slightly high’ mean increasing levels vs the previous 24hr index? I have had two of these monitors set up for the past week in bedrooms that are fed by an ERV that runs constantly. CO2 levels never go above 900 ppm despite two people sleeping in one of the rooms. But the TVOC values are constantly in the 37-100 range depending on how much human activity is going on around them (less in the middle of the night and more in the mornings and evenings). I almost never see green readings outside of the middle of the night where it can dip down into the high 30s. Should this be interpreted as constantly rising TVOC values day after day? Or am I fine as long as I stay out of the red? Or does this all ultimately not mean anything without knowing the specific VOCs causing the readings?
This is a great question and I will do my best to help.
I also would lean towards the AirGradient ONE if VOCs are a big cause of worry for you (see my other replies above). Again, I do work with AirGradient so please keep that in mind. However, I think when it comes to VOCs it’s one of the best monitors simply because users can choose between seeing the VOC index or absolute values as well as adjust the baseline.
A lack of an app is a frustration (for me, too!), but you can add the dashboard to the homepage of your iOS or Android device if you want. If a nice app is essential for you, however, I think the Qingping monitor might be the better bet!
If you are okay with only seeing PM values, the AirBeam 3 is a good, albeit pricey, device. If you want a monitor with a VOC sensor (with the usual caveats) and a better app, the Atmotube Pro is the best way to go. To be honest, you could also get an Atmotube Pro and use it in your home as an indoor monitor!
Hmm, this is a tough question! Do you have an air purifier with carbon filters? if so, you might be able to run that in a room for a while and calibrate there. If not, I imagine it’s quite hard to find a non-contaminated area. I will continue to think on this!
No problem! I think I may have overcomplicated this on accident, so let me try to explain it better. It’s not an easy topic!
Basically, even recent VOC sensors that typically output an index (like the SGP4x sensors from Sensirion) can have a formula applied to output an ‘absolute’ value. You can read more about how this works in this article that I recently helped write for AirGradient:
While this value is called absolute, Sensirion uses the index as the default for its sensors because ‘absolute’ values are often useless for reasons also outlined in the above article (lack of specificity, cross-sensitivity, environmental sensitivity, and baseline drift). However, with a formula applied, the SGP4x sensors can, technically speaking, give an absolute output - it’s just not very useful or reliable.
It appears that, yes, Qingping has converted the output (in Sensirion’s index) to an ‘absolute’ value and then back into another index…
As for this, I’m unsure of the answer. I will need to look into this further. I agree that it seems very odd for Qingping to convert to absolute values only to display another index.
I think I will need to contact Qingping again, or even ask if they can answer here because I agree - this is very confusing. Sorry I can’t give a better answer right now, but I’m glad you raised this point because I overlooked it!
I asked Qingping about this and got this response:
Don’t worry too much about the “past 24 hours.” Think of it as a self-calibrating sensor rather than a system strictly based on a 24-hour average.
Qingping’s evaluation standard is stricter than Sensirion’s, and this is simply the case (the conversion does not affect the index value itself).
You don’t need to worry when the indicator turns yellow. In fact, VOCs aren’t the same as harmful gases—for example, our bodies naturally emit VOCs.
It’s not great and doesn’t reveal much (I asked for the specifics behind how their index works).
I find a few phrases here interesting. Specifically, ‘rather than a system strictly based on a 24-hour average’ and ‘the conversion does not affect the index value itself’ which appear to imply that they’re doing more behind the scenes.
