AirSpot Review – A Tiny Carbon Dioxide Monitor That Can Be Worn as a Watch!

Many of us who are interested in carbon dioxide monitors await the day that the sensors can be shrunk enough to fit into a smartphone or smartwatch. While this technology is perhaps still many years away, we’ve seen some fantastic improvements in carbon dioxide sensor technology over the past few years that have allowed some ultra-small monitors to enter the market.

While still a far cry from being able to fit into a smartphone (and realistically, this is still a relatively niche function that will probably never be added), sensors like the Sensirion SCD4x series have drastically decreased the size that carbon dioxide monitors need to be. While some devices that rely on transmissive NDIR sensors (like the Aranet4 Home) can’t be shrunk down much (due to the limitations of measuring with light), these photoacoustic sensors have the potential to be much smaller and to fit into much smaller devices as they measure sound instead.

Until recently, the AirValent CO2 Monitor was the smallest all-in-one device that I had tried (meaning it includes a battery and has Bluetooth connectivity), but after receiving the AirSpot monitor recently, this changed. Not only is the AirSpot CO2 monitor smaller, but it is small enough that it can be worn as a watch with the optional watch strap – that’s pretty cool! Both monitors use the same Sensirion sensor, and it’s amazing what this shrinking of technology has allowed us to achieve.

Important note: The AirSpot CO2 monitor has rapidly changed in the past year. For example, many previous reviews mention older versions of the accompanying smartphone application. Since those reviews, much has changed with the device, and for that reason, my opinions and experiences will likely differ from older content. Please remember that, as of the time of writing, this review reflects the device’s current state.

Anyway, enough about the sensor itself. Believe it or not, today I’m actually here to talk about the AirSpot carbon dioxide monitor! This monitor is – to my knowledge – the smallest all-in-one carbon dioxide monitor currently on the market. While there are a few that are smaller, they don’t include internal batteries, and they mostly lack Bluetooth or WiFi connectivity. As such, this device is quite exciting.

However, as I mentioned just before, small carbon dioxide monitors have been becoming more common, so it isn’t this aspect that makes this device so interesting to me. Instead, it’s the ecosystem of accessories that has sprung up alongside the device itself. For example, if you purchase the optional extras, you can wear this device as a watch, mount it to your phone, or even put it on a keychain! This extra functionality makes this an exceptionally portable device, and it adds a level of convenience that sets the AirSpot CO2 monitor apart from its peers.

With this in mind, I am excited to present my AirSpot CO2 monitor review. This is a very promising device, and it has the potential to make carbon dioxide monitoring not just more accessible but also more convenient for many people. However, how does it hold up in the basics like accuracy, design, and battery life? In this review, I will answer these questions and more. As always, if you have any questions or comments, please share them in the comments below!

This post contains affiliate links. For more information, please refer to my affiliate disclaimer. I was NOT sent a product for review; I purchased this monitor myself. All opinions expressed in this post are my honest thoughts. I only recommend products that I believe in.

Information on this blog is for informational purposes only. Readers are encouraged to confirm the information herein with other sources. Furthermore, this information is not intended to replace medical advice from professionals. This website assumes no responsibility for the accuracy of the information, which is subject to change without notice. Devices mentioned on this website are not medical devices and do not guarantee protection.

Accuracy

One of the biggest complaints I heard about previous versions of the AirSpot carbon dioxide monitor was about its accuracy. According to the AirSpot team, the Sensirion photoacoustic sensor (which the monitor uses) has been quite challenging to get to an accurate and usable state. However, based on my experience with the device, it seems it is now almost there.

As mentioned, the AirSpot carbon dioxide monitor uses a Sensirion SCD41 photoacoustic NDIR sensor. This ultra-compact sensor is quite popular in small carbon dioxide monitors such as the AirValent CO2 monitor and CO2 Click Model F. While it is a good sensor that provides accurate readings (when calibrated correctly), it does have a few caveats that we will discuss later in this section. However, for now, it’s worth noting that this is a trusted and typically accurate sensor from a reputable brand.

The stated accuracy of the device, as given by AirSpot, is ± 40 ppm ± 5% of reading. However, this should be a worst-case accuracy specification, as Sensirion states that the SCD41 has an accuracy of ± 50.0 ppm ± 2.5 % of reading under 1000 ppm and ± 50.0 ppm ± 3.0 % of reading at 1001 – 2000 ppm. It’s only at readings > 2000 ppm that the ‘worst case’ ± 40 ppm and ± 5% of reading accuracy value is used. Of course, I wanted to test this a little bit and see for myself how the device performed.

While I don’t have the tools to run any scientific comparisons (although I wish I did!), I have a range of consumer-grade carbon dioxide monitors that I can use as a reference point to compare the AirSpot device to. In my testing, I chose both the Aranet4 Home (considered the gold-standard of consumer-grade CO2 monitors) and two AirValent CO2 monitors (which also use the SCD41) for comparison. Throughout my testing, I had some interesting findings.

Firstly, I attempted to calibrate all four monitors in exactly the same conditions. Since the SCD41 is sensitive to sound and, therefore, can be impacted by wind or a breeze blowing through the device, I placed all of the monitors in a cardboard box for shelter. I then placed this outside for around 10 minutes before triggering the calibration process on each device. Interestingly, despite trying to calibrate the devices identically, I found the AirSpot monitor to read higher than not just the Aranet4 Home consistently but also the AirValent monitors.

I tried calibrating the monitors several times, and I couldn’t quite figure out what was causing this difference. However, I believe it may have been due to a slight difference in baseline calibration levels. Luckily, with the AirSpot monitor, the baseline is adjustable, and this is something that can be overcome with this feature. I also noticed that this difference between default calibrations became much less significant following the recent update.

I carried out a week-long comparison with four monitors involved, but I kept running into data reporting issues (not with the AirSpot device, mind you), making a longer comparison very hard to visualise without gaps. However, I checked each of the monitors multiple times every day, and I found that, with the default calibration settings and identical calibrations across each device, the AirSpot monitor almost always read 40-100 ppm higher. By decreasing the baseline value, I was able to solve this issue, but I hope the default baseline and calibration can be improved in the future.

When adjusted, I found the readings were generally very accurate and closely tracked with readings from other NDIR devices. However, I also noticed that the AirSpot CO2 monitor has some seemingly random spikes in measured concentration. These spikes are very obvious – for example, the monitor will consistently record 1000-1500 ppm, and then a single reading will show 5000 ppm. This happened relatively frequently during my time with the device, and I had a feeling it was because of the photoacoustic sensor.

The images above show some of these random spikes. During all of them, the device was in my bag, and there were no other actions that would account for these spikes at the given times.

Basically, photoacoustic sensors can also be influenced by sound, and this can lead to the spikes I saw in my data. When these spikes occurred, I normally had the monitor in my backpack, and when I reached out to the team at AirSpot, they said my guess about this being caused by sound was probably correct. I don’t mind these spikes too much because I know not to pay attention to them, but I have also been told that the team is working on removing these single, extreme spikes.

Despite using many other SCD41 devices, I’ve never seen such obvious spikes, and I believe this may be due to the fact that the SCD41 in the AirSpot monitor is so exposed. While inside the device, there is a lot of venting around the sensor, and it ends up being quite exposed. While I believe this issue will be fixed soon (using an algorithm to pick up erroneous readings), I wanted to note this as I experienced it in my day-to-day use.

The SCD41 supports automatic baseline calibration (explained below) and manual calibration. Depending on how you use the device, I recommend disabling automatic calibration. Personally, I prefer to calibrate manually when the readings begin to drift. It’s also worth noting that you can reset your AirSpot monitor to the factory calibration if you’re worried you’ve made a mistake. I believe many users will appreciate this fallback, as it means you can never truly mess up with calibrating the device.

Overall, the AirSpot CO2 monitor is an accurate device with a few caveats in its current state. While it did take me a few attempts to bring the readings in line with my other devices, I was able to do this, and afterwards, the device was consistently very accurate. I know the team is actively working to improve the accuracy of the device further, and I’m confident they can fix this.

While the spikes in readings (due to sound) are a bit frustrating to see (they make the historical data look a lot more dramatic than it actually is), they seem to only occur for a reading or two in a row so it’s still easy to identify overall trends. With that said, I am looking forward to a fix for this issue, and I have been told that it’s being actively worked on.

Design

AirSpot (left) and AirValent (another tiny monitor).

The AirSpot carbon dioxide monitor is a very compact device that comes in far smaller than the previous smallest carbon dioxide monitors I had tried – the AirValent and AirValent TravelLite (pictured above). Don’t get me wrong, both of these monitors are still small, but the AirSpot monitor takes size (or the lack thereof) to a new level. While there may still be some smaller monitors out there, none of them (that I know of) also have a built-in battery and connectivity. As such, the AirSpot carbon dioxide monitor has a very unique selling point in its size.

This size enables some other very cool features, which I briefly alluded to in the introduction. For example, the AirSpot carbon dioxide monitor can not only be used as a small, handheld monitor, but you can even attach it with a mount to the back of your phone, attach it to a keychain, or wear it on your wrist with the optional watchstrap accessory. This little ‘ecosystem’ of accessories is very cool and allows the AirSpot monitor to have a convenience unparalleled by any other carbon dioxide monitor to date.

I tried all of these accessories, and while I opted to just use the device by itself (and sometimes with the keychain, which I attach to my bag), in the end, I love having these options available. Personally, I didn’t particularly like wearing the wrist strap because the device is a bit too big on my wrist, but having the option available is fantastic. I also think a popular attachment will be the phone/wall mount, which allows you to ‘dock’ the monitor anywhere you want.

Now, I will say that both the monitor and all of these accessories feel quite ‘plasticy’, and I don’t think the quality is fantastic. That said, they’re also quite affordable, and they are durable enough that neither the monitor nor accessories have broken after the four or five months I’ve been using them. However, I do remember that my first impressions of both the device and accessories were not great.

I also have a feeling that this may have been a purposeful decision, as the device itself weights almost nothing at only 17 gra. Yes, it really is that light! Anyway, I imagine this weight was only possible with plastic materials, and it wouldn’t make sense to match a super lightweight device with a heavy wrist strap or keychain. I guess it’s as a balance as with everything. Therefore, while I do feel that the device and accessories feel a bit cheap, I understand why this decision was made and I believe many people will appreciate this.

That said, after using the monitor and (primarily) the keychain for quite a few months now, I’ve been happy with how well they’ve both held up. Despite being plastic, the device is still in good condition. Any damage is purely cosmetic, such as some scratches on the screen and back of the device – even after putting this monitor in my backpack every day for weeks. Therefore, while the device is super light and made from plastic, I think the build quality is okay.

Moving on from the build quality, let’s look at the design of the device. As mentioned earlier, this device is very small but large enough to sport a USB Type-C port, home button, and a decently-sized screen. In fact, despite being so small, I like the size of the device and find it easy to use. The button, for example, is small but still large enough that I can easily press the button without issue. It also has a nice click, which makes pressing it feel responsive.

On both sides of this button, as well as on the bottom of the device, are vents which allow air to enter the device. This is common across all carbon dioxide monitors, as they need a way to measure the carbon dioxide concentration in the air. Of course, this means that the device isn’t waterproof or resistant, and you will need to be careful to ensure it never gets damp. Please remember that this isn’t unique to the AirSpot monitor and applies to all carbon dioxide monitors. However, it is important to remember with a device this portable, I find it more likely to get wet than less portable devices, which typically stay at home.

Above the button and vents is a screen which shows not only the current carbon dioxide concentration but a historical graph (if you have the feature enabled in the app) but also shows the time, some status icons (alarm, vibration, etc.) and the battery life. By default, the screen will stay off, and when you press the button, the screen will turn on for a few seconds. While this can be changed in the settings, I’ve kept this default setup as it gives me good battery life. It’s also worth noting that even when the screen is off, the device will continue to take readings and communicate with your smartphone via Bluetooth.

Now that I’ve mentioned the battery life, let’s briefly discuss that. As surprising as it may seem, considering the size of the device, it actually has quite a decent battery life. I set my device to take a measurement every minute, and I get enough battery life to easily last me a week – especially if I’m only turning on the screen a few times a day. I also believe the battery life may be better than what is stated in the image above, as I’ve found my device lasts a very long time, even taking a reading every minute.

Overall, despite not having great initial impressions, I am quite happy with the design of the AirSpot CO2 monitor. I’ve used it every day for quite a few months now, and over time it’s grown on me a lot. While many other CO2 monitors share a similar design in some ways, I really like some of the unique aspects of the AirSpot monitor, such as being able to see historical data on the screen.

App & Connectivity

When I first received the AirSpot monitor, the app was admittedly far from great. However, since then, the app has undergone major updates, and my review of this device has been carried out on a beta version of the application that will soon be live for all users. Please keep this in mind, as it means that my experiences with the device and application are very different from the reviews and experiences before March 2025.

Upon opening the app for the first time, you will be met with a screen for pairing an AirSpot device. Since my device was already powered on, the device instantly showed up on the app, and I had a painless experience pairing my iPhone with my AirSpot CO2 monitor. Since this connection is made and maintained via Bluetooth, you will want to ensure Bluetooth is enabled on your smartphone.

Unlike most carbon dioxide monitors, if you want to use this device, either standalone or only with an infrequent Bluetooth connection, it performs very well. For one, the device has a historical data graph on its home screen, meaning that even if you use the device standalone, you can still view CO2 concentration trends. Secondly, and even more usefully, the device has enough internal storage to locally hold one week’s worth of readings at 5-second intervals. This means that you won’t lose data even if you only connect the monitor to your phone once per week. Fantastic!

Once you’ve added a device to the app, you will be met with the home screen, which holds a surprisingly wide range of options and information. Not only will you get a ‘devices’ menu (more on this soon), but you can also view Clean Air Mapping (Ravenmap if you’re already familiar with it), set up the app, view information on solutions for improving your air quality, visit the AirSpot store, and see news related to clean air. While there’s a lot of information under each of these tabs to delve into, it’s instantly apparent that this app has a wealth of information and settings and was created by a team passionate about clean air.

So, let’s start with the tabs one by one. At the top, we have the ‘devices’ tab, which is probably the screen you will be visiting the most. Here, you can find the information from your connected monitors – in my case, just one. I can see the current battery level and carbon dioxide concentrations at a glance, and I can also request a CO2 reading update. This is an awesome feature and something I haven’t seen on any device except for the Aranet4 Home.

At the top-right of the monitor card are a few buttons – one for viewing historical data from the device and one for device settings. On the historical data tab, you can see CO2 concentration data from different periods. Since this graph can show quite long periods of data, it’s very useful that you can quickly zoom in and out to get exact readings for any given time. Interestingly, it doesn’t seem possible to see temperature or relative humidity data, even though this sensor provides it.

The graph also offers a few options that allow you to show threshold lines (good air quality, mediocre, and poor), and you can also add a third axis to show the percentage of rebreathed air at any given time. All in all, it’s quite a powerful in-app graph, and I don’t think many people will feel the need to export data. Oh, and yes, you can export data to a .CSV file if you want to analyse it in more detail. With that said, even the exported data lacks temperature and relative humidity data.

The device settings allow you to do everything from enabling alarms and vibrations to calibrating the device. Again, the extensive list of settings makes it seem like this app (and the device itself) was designed by people passionate about clean air. That is to say, while it’s an easy app to use for beginners, it has very powerful settings and features that I appreciate as a ‘power user’.

A good example is the calibration menu, which allows you to toggle autocalibration on or off or manually calibrate the device. While this isn’t unusual, what I really appreciate about this menu is how it lets the user set the calibration target. This is handy because ambient carbon dioxide levels are not consistent around the world, and if you know your outdoor concentration (using a website like Nullschool), you can fine-tune the calibration down to single digits. This is also a very cool feature and will impact automatic calibrations.

Importantly, you can also change the measurement interval and the device’s display settings in this menu. AirSpot allows you to take measurements as frequently as every five seconds to as slow as every three minutes. If you want to conserve battery life, you can even disable readings entirely until the button on the device is pressed. Furthermore, there are also settings to change the display behaviour, allowing you to always keep the screen on if you want. These settings are handy for allowing the user to balance measurement frequency and battery life.

There are a few other settings in this menu, too, but for the sake of keeping this article readable, I can’t delve into everything here. However, I can say that there are many settings here, and you can customise the device in many ways that you can’t with other monitors.

Now, let’s go back to the home screen. The second option here allows you to access Raven: CleanAir Map, a community-powered app for indoor carbon dioxide concentrations. If you visit a public place, you can record the carbon dioxide concentration and upload it to the map. This allows others to decide if they should visit based on the risk. I’ve always found these maps quite inconvenient (to remember to upload data to), so having it built into the app is very handy.

Another aspect that I appreciate about the app is that it provides news and information on indoor air quality and what you can do to improve it. While the links will take you to the AirSpot website (as opposed to keeping the information in-app), many people will appreciate having this information within easy reach. I also appreciate how much work must have gone into creating these resources so that all users can fully understand their monitor and the actions they can take based on the readings it provides.

Since the app update, I also haven’t noticed any major issues or bugs. Actually, I haven’t even noticed any minor ones! This is a vast improvement over previous versions, and I’m very happy to see this device becoming more usable. If you already have an AirSpot device but stopped using it due to previous issues, I think it’s time to try it again. If you’re considering purchasing one, know that the app provides a good user experience and contains a wealth of information.

Pricing & Competition

The AirSpot CO2 monitor is just over $140 USD, meaning it’s among the more ‘premium’ segment of the carbon dioxide monitor market. At this price, it’s comparable to devices like the INKBIRD IAM-T1, Aranet4 Home, and AirValent CO2 monitor. While I don’t think this price is unreasonable for the Airspot monitor, there’s no denying that the other devices in this price range are very well-rounded, meaning that there is a lot of competition.

Firstly, let’s discuss the unique benefits of the AirSpot CO2 monitor. Obviously, it’s the smallest device out there – regardless of price range. If having a small, discreet monitor is essential for you, that alone might be enough to justify the price. On top of this, the AirSpot monitor brings together many advanced features that other monitors feature, but in a single device. For example, it brings the instant reading feature from the Aranet4 Home and merges it with good internal storage and custom calibration baselines – something which, as far as I remember, isn’t available on any of the three aforementioned devices.

These points, among others, make the AirSpot CO2 monitor a unique proposition as it has a range of features that other devices in this price range don’t have. While there are also some features that this device lacks compared to the competition (such as Home Assistant integration, which the Aranet features, or an E-ink screen, which all three of the other devices have), it’s up to you to judge which feature set is more important for you.

As for the similarities between the devices, they all perform well in terms of the essentials. They all allow for manual calibration, data exporting, historical data viewing, and more. At the end of the day, I believe all of these devices are well-rounded – which they should be at this price point! That said, I believe the AirSpot CO2 monitor offers advanced features above the other monitors.

I think other devices, especially the Aranet4 Home, still have a more polished experience (especially before the recent AirSpot app update), but there is no denying that the AirSpot CO2 monitor has a great feature set. In this way, it reminds me of the Air-Q Basic that I recently reviewed which is a great device for users who want to have full control over their experience.

The only feature that I really think is lacking at the moment and that I believe needs to be added is the ability to see and graph other parameters from the SCD41 sensor. Namely, there should be a way to see the temperature and relative humidity. While these metrics aren’t as important as CO2, I still think the user should be able to access them, and it’s disappointing that there currently isn’t a way to view data for these metrics.

To conclude this section, I believe the AirSpot CO2 monitor is fairly priced. While it is a premium monitor (based on its price), it offers similar features to other monitors in this price range while being smaller, and sometimes far smaller, than the competition. If portability is important to you, there is no better monitor on the market. If you just want a monitor that does the basics well, this monitor is also deserving of your consideration.

Conclusion

A few years ago, I dreamed of a device like this. One small enough that I could pop it into my pocket without really thinking. While AirValent has a small device, it’s still quite weighty and adds a noticeable heft to my pocket if I put it there. AirSpot has gone a step further and created a device that’s both smaller and incredibly light. I truly can place this monitor in my pocket, backpack, or sling bag and forget that it’s there – until I need to check the CO2 concentration quickly.

I’m also a big fan of the portable and convenient approach, which is shown by the accessories that AirSpot offers. While I would love to see more accessories added over time, the three that are currently offered give (at least compared to other monitors) limitless possibilities for how the monitor can be used. I would love to see a few more accessories added, such as a case (basically the key ring case without the key ring). While this would add a bit of bulk to the device, I think many users would appreciate the extra durability of a plastic case.

When it comes to the feature set, the AirSpot CO2 monitor is very well-rounded – as it needs to be for this price. It combines some of my favourite features from other monitors in one great package. With that said, it lacks a few things (such as temperature and RH readings), which I believe need to be added for this monitor to go from good to great. However, even in its current state, since the release of the new application, I can recommend this device as I believe it will suit many people’s needs.

If you’ve read through this review and have some remaining questions, please don’t hesitate to ask them in the comments form below. I always do my best to reply to all comments! On the other hand, if you’ve tried this device yourself and have some thoughts to share, I would love to hear those, too. Thank you for reading!

AirSpot CO2 Monitor FAQ

AirSpot Review - A Tiny Carbon Dioxide Monitor That Can Be Worn as a Watch!

Discover the AirSpot CO2 Monitor, the smallest all-in-one carbon dioxide tracker with Bluetooth connectivity and versatile accessories. Is it the right portable air quality solution for you? Find out more!

Product Brand: AirSpot

Editor's Rating:
4

Pros

• Ultra-portable design, smallest all-in-one CO2 monitor available
• Multiple accessories for versatile usage (watch, keychain, phone mount)
• Customizable calibration allows users to fine-tune accuracy
• Stores up to a week’s worth of CO2 data internally
• High-frequency CO2 readings with adjustable measurement intervals
• Well-designed mobile app with advanced features and historical data analysis
• Compact, lightweight, and easy to carry anywhere

Cons

• Occasional reading spikes due to sensitivity to sound
• Lacks temperature and humidity tracking despite sensor capability
• Plastic build feels less premium compared to some competitors
• Shorter battery life compared to some larger CO2 monitors
• No smart home integration (e.g., Home Assistant support)
• Premium price ($140), making it one of the more expensive options