Despite being available for many years, carbon dioxide monitors have only recently gained widespread attention. These handy devices – perfect for identifying poorly ventilated indoor spaces – have now found their way into thousands of individuals’ pockets, backpacks, homes, and offices worldwide. As awareness around indoor air quality continues to grow, CO2 monitors are quickly becoming essential everyday tools for many people.
That said, the growing popularity of these devices has brought with it an overwhelming number of options. With so many models on the market, it can be difficult to know which one to choose. Some monitors are portable, some come with companion apps, and others boast a variety of features – but which ones actually provide accurate carbon dioxide readings? That’s the question many people are trying to answer.
Having spent years working with carbon dioxide monitors, I decided to create a guide featuring what I consider the best monitors for different needs. I’ve personally tested every device included in this list, and I’m only recommending models I’ve had first-hand experience with. While this means the list isn’t exhaustive, it does include many of the most popular and reliable consumer-grade options available today. I’ve intentionally left out any monitors I haven’t used myself, as I believe it wouldn’t be right to recommend something I can’t personally vouch for.
Now, it’s important to note that this article is specifically geared toward consumer-level users. If you’re a professional needing a high-accuracy, lab-calibrated device, you’ll want to explore NIST-calibrated options like those offered by Forensics Detectors. Those kinds of monitors are built for a different audience and serve more specialized purposes.
But if you’re looking for a more accessible, user-friendly monitor – something to help you understand ventilation quality, viral transmission risk, or even how CO2 might be affecting your concentration – you’re in the right place. These consumer-grade devices are practical, approachable, and ideal for day-to-day use in homes, classrooms, offices, and more.
As always, I welcome your input. If there’s a carbon dioxide monitor you think deserves a spot on this list, I’d love to hear from you on the forum. This list is always evolving, and I’m eager to explore new options that others have found useful. Now that the housekeeping is out of the way, let’s dive into the recommendations!
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Why Should I Monitor Carbon Dioxide?
The first question we need to answer before diving deeper is obvious – why should I even be bothered monitoring carbon dioxide? Well, with a growing body of research showing how harmful carbon dioxide can be, even at levels commonly found indoors, the importance of monitoring the gas becomes increasingly clear. It’s not just an environmental concern (as many assume); it impacts our health and well-being in everyday situations. Simply put, there’s ample evidence supporting why we should all be paying closer attention to CO₂.
Carbon dioxide monitoring has recently been getting much more attention, especially due to its connection to viruses. Studies have shown that carbon dioxide levels can be a proxy for the likelihood of viral transmission. In other words, when you’re in a public space – or really any shared space – high carbon dioxide levels can indicate a higher risk of viral transmission. This makes carbon dioxide a simple and accessible way to keep tabs on how well a space is ventilated and, in turn, how safe it might be.
Of course, while COVID-19 is still receiving most of the attention in this space, carbon dioxide monitors have far more use than just alerting us to potential virus exposure. Since carbon dioxide levels reflect the overall quality of ventilation, they can also serve as indicators for the transmission potential of other airborne illnesses. Better air quality equals lower risk, whether it’s the flu or something else.
This makes carbon dioxide monitors particularly valuable tools in identifying spaces with poor ventilation. Once you know a room is poorly ventilated, you can make informed decisions – like opening a window or wearing a mask – to reduce your exposure risk. Even just knowing when to leave a space can make a significant difference in protecting your health.
Still, it’s important to recognize that COVID-19 isn’t the only reason to track CO₂ levels; arguably, it’s not even the most important reason. While the pandemic brought these devices into the spotlight, the long-term effects of carbon dioxide on our bodies and minds are just as pressing. Monitoring carbon dioxide is important for improving everyday life, not just avoiding illness.
That’s because carbon dioxide has a surprisingly wide range of effects on its own. It’s been linked to drowsiness, disrupted sleep, reduced cognitive performance, and more. While these issues might sound minor on the surface, they can seriously impact productivity, learning, and overall quality of life.
A Harvard study showed that cognitive performance can drop by 50% at just 1400ppm (parts per million) of carbon dioxide. That’s not an especially high concentration – it’s a level you could easily encounter in a poorly ventilated area, like a bedroom, bus, or café. If you’re reading this in a space with closed windows and other people around, there’s a good chance you’re already feeling the effects.
The same study also found that even at 950ppm – an even more common CO₂ level – cognitive performance can decrease by around 15%. That’s a significant drop in mental sharpness and efficiency just from spending time in a space with inadequate airflow. We often blame tiredness or lack of focus on other factors, but poor air quality may be the real culprit.
On top of that, prolonged exposure to elevated indoor carbon dioxide levels has been linked to more serious physical health effects. These include increased stress, kidney calcification, and bone demineralisation – all of which can be mitigated by simply ensuring good ventilation. That’s a powerful argument in favor of monitoring this invisible gas.
The broader impacts of carbon dioxide on human health are still being explored, and the field continues to evolve rapidly. For a long time, indoor carbon dioxide was overlooked as a health factor, and only recently has it been acknowledged in public discourse. With more research underway, we’re just beginning to understand how much this one gas can influence our lives.
That said, even with ongoing studies, we already know enough to conclude that monitoring carbon dioxide is important. Whether to reduce the risk of airborne illnesses or keep your brain functioning at its best, a CO₂ monitor offers valuable insights. Without this information, it’s all too easy to unknowingly accept poor indoor environments as normal – at the expense of your health and performance.
Features to Look For in a Carbon Dioxide Monitor
When it comes to purchasing a carbon dioxide monitor, there are a few factors you’ll want to keep in mind. While these aspects individually don’t guarantee a good product, all good products have these features in common.
Please keep in mind that these are just the bare essentials. Depending on your preferences, you may also want to look for a carbon dioxide monitor with other features, such as a large screen or good portability. Here are a few minor features worth looking out for, depending on your preferences:
- Connectivity
- Configurable alarm/notification thresholds
- E-ink screen (visible + long battery life)
- Compact size
- Rechargeable battery
- Updateable
1. NDIR Sensor
NDIR Sensor. Image source.
NDIR stands for non-dispersive infrared; these sensors are the gold standard for carbon dioxide monitoring. These sensors have a chamber where air enters – normally passively, but some monitors will have an intake fan. Once the air is inside the chamber, a beam of light specifically set to the wavelength of carbon dioxide will be activated. On the opposite side of the chamber, a receptacle monitors how much light makes it across the chamber.
Since carbon dioxide absorbs the light (at around 4 microns in wavelength), monitoring how much reaches the other side of the chamber indicates how much carbon dioxide is present in the air. While NDIR sensors can drift over time (which is why you’ll want a device that features manual recalibration), they tend to remain accurate for many years due to how they measure the gas.
The two other common sensor types are metal oxide semiconductors and electrochemical sensors. However, both of these sensors can be thrown off by other substances in the air that can impact readings. Furthermore, they tend to drift more than NDIR sensors, especially electrochemical ones.
It’s worth noting that photoacoustic sensors have recently gained some attention. These sensors cost around the same as NDIR sensors and are also accurate, but they have a few caveats (they tend to lose accuracy at higher temperatures – however, this shouldn’t make much of an impact since these monitors are usually used indoors). Photoacoustic sensors are common in devices where a small size is the priority, as they’re much smaller than NDIR sensors. If you keep in mind their limitations in warmer temperatures, they can also be very accurate.
2. Manual Recalibration
A lack of recalibration can lead to skewed readings.
While NDIR sensors are known for their accuracy, they aren’t without their flaws. One of the most common issues they face is something called sensor drift. Over time, it’s very possible – and likely – that your carbon dioxide monitor will begin to deliver slightly skewed readings. This gradual shift in accuracy is what we refer to as sensor drift, and various environmental and operational factors can influence it.
Because sensor drift can affect any consumer-grade carbon dioxide monitor, it’s important to have a way to correct it. The most effective method is to recalibrate your device occasionally. Regular manual calibration helps maintain the accuracy of the readings and ensures that your monitor continues to provide reliable data over time.
The good news is that the recalibration process is usually quite simple. In most cases, it just involves taking your monitor outside and letting it sit for a few minutes. This allows the device to re-establish a baseline using outdoor atmospheric carbon dioxide levels, which typically sit around 420 ppm, though this can vary slightly depending on location and conditions.
For this reason, it’s crucial to choose a carbon dioxide monitor that supports manual calibration. While some monitors advertise auto-calibration as a convenient feature, it can actually lead to problems – especially if the device isn’t regularly exposed to fresh outdoor air (read more on that below!). Without that outdoor baseline, auto-calibration can reinforce already inaccurate readings, ultimately doing more harm than good.
💡 Autocalibration: Some carbon dioxide sensors and monitors implement autocalibration, a feature that prevents sensor drift (sensors slowly losing accuracy over time) by regularly calibrating the device.
This can cause issues because, on a set interval, the sensor will perform ABC (automatic baseline calibration), which sets the lowest carbon dioxide concentration the device has been exposed to as the baseline (typically 400 or 420ppm). This isn’t an issue if a monitor is regularly exposed to ambient air (around 420-430ppm). However, suppose the device is in a room or location where the carbon dioxide levels do not reach ambient every calibration cycle (typically seven days). In that case, it can incorrectly set a baseline, which throws off all readings until the next automatic calibration.
If your monitor regularly goes outside or is in a room that often sees ambient or near ambient CO2 levels, ABC can be very useful. If not, I recommend disabling the feature.
3. Single-Beam or Dual-Beam
Dual-beam NDIR. Image source.
As mentioned earlier, NDIR is the gold standard when it comes to carbon dioxide sensing – but it’s worth noting that there are different types of NDIR sensors, each with its own characteristics. Among them, you’ll find single-beam, dual-beam, and photoacoustic NDIR sensors. All three operate using different methods, but they’re all capable of delivering reliable, accurate results when implemented correctly.
The two most common types of transmissive NDIR sensors are single-beam and dual-beam. Both function on the same core principle of measuring infrared light absorption and can be equally accurate. The difference lies in how dual-beam sensors include a second, internal reference beam – usually triggered once per day – to help keep the primary sensor in check.
This reference beam is factory-calibrated and isn’t used during standard measurements. Instead, it’s there to help recalibrate the main sensor, which is constantly in use and more prone to drift over time. In theory, this setup allows the monitor to maintain higher accuracy for longer periods without the need for manual calibration – at least when the device is newer.
That said, even the advantage of dual-beam design has its limits. According to Senseair, a well-known manufacturer of both sensor types, dual-beam NDIR sensors don’t maintain accuracy indefinitely. While they may perform better out of the box, external factors like environmental exposure, aging, and general wear can still cause sensor drift over time.
So, while some companies like to highlight dual-beam NDIR as a must-have feature, it’s far from essential. In the long run, both single-beam and dual-beam sensors will require calibration and tend to offer similar accuracy. The main benefit of dual-beam sensors is their hands-off accuracy when new, but whether single-beam, dual-beam, or photoacoustic, they can all perform well with proper care and calibration.
4. Historical Data
Aranet, AirSpot and AIRVALENT applications
You can typically view and analyze data from carbon dioxide monitors in two main ways. The first is directly on the device itself. While this might be convenient for quick checks, it comes with a major limitation: you only see the CO2 concentration at that exact moment. If you’re relying solely on the device’s display, usually there’s no way to look back at past readings or identify trends over time.
Fortunately, many higher-end and mid-range devices address this limitation by offering app support or the ability to export data. This feature is incredibly valuable, letting you track and analyze CO2 levels over time. For example, if you’re curious whether carbon dioxide concentrations spike while you’re sleeping or during work meetings, historical data makes that analysis possible. Without this capability, it’s hard to draw any conclusions beyond what you observe at the moment.
Nearly all of the devices included in this list support some form of historical data access via a companion app. Some go a step further by offering a web dashboard view, where you can explore long-term trends more easily on a larger screen. A few even allow you to export data to spreadsheets for deeper analysis or reporting. Whether you’re trying to monitor ventilation or air quality in your home, office, or classroom, having access to this kind of data can be a game changer.
Therefore, I strongly recommend choosing a monitor with this feature if your budget allows it. It turns a simple reading tool into a powerful device, helping you make more informed decisions about air quality. In the long run, it’s a small upgrade that delivers a lot of value – especially if you’re serious about understanding and improving the spaces you spend time in. That said, there are times when you may only want a simple device (especially if you plan to give it to your child to use at school), so I have included a few monitors without this feature on the list.
5. Other Sensors
Sensors and accuracy on the Aranet4.
Most carbon dioxide monitors come with more than just a CO2 sensor. In fact, nearly every device on this list also includes sensors for relative humidity and temperature. While these aren’t strictly necessary for monitoring carbon dioxide, they’re valuable additions that offer a complete picture of indoor conditions. CO2 levels are a great way to assess ventilation, but having temperature and humidity data alongside them helps you better understand overall air quality and comfort.
Some monitors offer even more advanced sensor arrays in addition to these standard sensors. A few devices on this list include sensors for PM2.5, PM10, tVOC (total volatile organic compounds), atmospheric pressure, and other parameters. These extra sensors aren’t essential for carbon dioxide monitoring, but they’re fantastic if you’re looking for a more general-purpose indoor air quality monitor. They allow you to track pollutants that can affect your health and well-being in different ways, especially in enclosed environments.
When choosing a carbon dioxide monitor, ask yourself: Do I need these additional sensors, or would I find them useful? If the answer is yes – or even “maybe” – then it’s a good idea to consider a device that includes them. Monitors with expanded capabilities can be especially helpful in environments like schools, offices, or homes where you want a broader view of air quality beyond just CO2.
It’s also worth noting that nearly all CO2 monitors include temperature and humidity readings because those measurements are typically derived from components already present in the CO2 sensor module itself. However, only some devices include a built-in atmospheric pressure sensor. This may not seem like a big deal at first glance, but it’s actually quite important for people living at higher altitudes. Atmospheric pressure can significantly impact CO2 readings, and without accounting for it, measurements can become inaccurate. Here’s a full forum thread diving deeper into this topic, which you can read if you want – but if you live in a high-altitude region, a pressure sensor is something you’ll definitely want to look for.
Lastly, while this guide focuses primarily on carbon dioxide monitors, I’ve included a few more well-rounded air quality monitors that offer additional environmental data. Devices like the AirGradient ONE, Qingping Air Quality Monitor Gen 2, and Qingping Air Quality Monitor Lite provide readings for PM2.5, PM10, and more. These are great options if you’re looking to monitor a wider range of air quality metrics. For a full list of indoor air quality monitors beyond CO2-focused devices, be sure to check out my separate article dedicated to that topic.
6. Battery Life
The Vitalight Mini CO2 Detector has an eight-hour battery life with Type-C charging.
When it comes to carbon dioxide monitors, battery life can vary dramatically – so much so that calling it inconsistent might be an understatement. Some monitors only last a few hours on a charge, while others can run for months or years without recharging or battery replacement. The range is vast, and choosing the right battery life depends on how and where you plan to use your device.
If you’re looking for a monitor that will stay in one place – say, on a desk at home or mounted in a classroom – then battery life might not be your top priority. In these cases, a device with a short battery life or one that plugs into a constant power source will work just fine. However, if portability is important to you – whether you’re commuting, working in different locations, or just want something you can toss in a backpack – you’ll want to prioritize a model with extended battery life.
It’s also important to consider how the device is powered. Some monitors rely on AA or AAA batteries, while others are rechargeable via USB. If you’re going for a rechargeable option, it’s worth checking what kind of USB connection it uses. While many users aren’t too picky, others prefer the convenience and universality of USB Type-C. A familiar and easily accessible charging method can make a big difference, especially for frequent travelers or everyday portable use.
Another key factor to remember is that some monitors’ battery life can vary depending on the frequency at which they take readings. For example, a device that updates CO2 levels every few seconds will consume more power than one that updates every few minutes. Many monitors allow you to adjust this setting, giving you the flexibility to prioritize either data granularity or battery longevity based on your needs.
Best Carbon Dioxide Monitors
Livegrid: carbon dioxide monitoring turned into art.
Now that we’ve discussed which elements are important to look for in carbon dioxide monitors, let’s discuss some recommendations! Carbon dioxide monitors come in all shapes and sizes. For example, would you believe it if I told you that the image above shows a carbon dioxide monitor? Well, to be honest, calling it a carbon dioxide monitor doesn’t do it credit, but yes, it has a CO2 sensor inside it. It’s also one of the coolest devices I’ve ever reviewed, and I recommend checking out my review if you get a chance (Livegrid review).
Anyway, my point here is that carbon dioxide monitors come in many forms and have very different niches and target audiences. As such, I’ve done my best to categorise the monitors that have made this list. The first few sections cover my overall recommendations at different price points, and the following monitors are my favourites for more niche purposes.
Best Carbon Dioxide Monitor ($150+)
Prefer video? Watch my YouTube review here.
If price isn’t an issue, the Aranet4 is a monitor you’ll want to check out. While it sold for around $150 before the pandemic, its rapid increase in popularity led to a massive price increase of up to approximately $250. Thankfully, the price has recently been dropping due to increased competition, and it’s often found on sale for under $200. While I’m not a fan of the price hike – it’s a lot for a device with such a niche purpose – there is no denying that Aranet4 has set the standard for consumer-grade carbon dioxide monitors.
There are two models of the Aranet4 – the Home and Pro. For nearly everyone, the Home is the monitor to check out. However, if you are in a situation where you want to use multiple monitors with a base station, the Pro is the monitor you’ll want to opt for. Besides this increased connectivity, both monitors are essentially the same.
So, what makes the Aranet4 the most popular carbon dioxide monitor? It has incredible battery life (as long as four years!), a highly accurate NDIR sensor, a fantastic accompanying app, and is super easily pocketable. On top of this, it even receives over-the-air updates, meaning new features are added over time.
You’ll also find a relative humidity, temperature, and atmospheric pressure sensor alongside the carbon dioxide sensor. These sensors can monitor the environment or discover relationships between carbon dioxide and other variables. Combined, these features, sensors, and more make the Aranet4 a solid offering.
The Aranet4 also sports a few features that other carbon dioxide monitors on this list don’t. For example, the Aranet4 can take on-demand CO2 concentration readings via the app. This is incredibly useful for situations in which you want to know the conditions straight away.
What about the downsides? Well, the most obvious downside is the price. The Aranet4 is the most expensive carbon dioxide monitor on this list; the price isn’t justifiable for many. On top of that, the device can only use AA batteries – there’s no internal, rechargeable battery. The price of these can quickly add up if you have your monitor set to take measurements at short intervals.
However, it’s hard to find disadvantages to the Aranet4 other than the price. The device is excellent both on its own and with the accompanying app. Furthermore, it supports manual calibration and stores 30 days of data on your paired smartphone. Perhaps its biggest advantage, however, is that it is super portable. The only more portable device on this list is the Vitalight carbon dioxide monitor!
- Incredible battery life (up to four years)
- Highly accurate NDIR sensor
- Fantastic accompanying app
- Includes relative humidity, temperature, and atmospheric pressure sensors
- Can take on-demand CO2 concentration readings via the app
- Expensive
- Only uses AA batteries, no internal rechargeable battery
- Build quality feels lower than some monitors on this list
Best Carbon Dioxide Monitor ($100 – $150)
If the pricey Aranet4 Home is within your budget, that’s also your best choice for a portable carbon dioxide monitor. However, if your budget doesn’t quite stretch that far, the significantly cheaper INKBIRD IAM-T1 offers 95% of the Aranet’s functionality at a lower price.
The IAM-T1 is clearly inspired by the Aranet, and I don’t think it’s a bad thing. While the device is slightly larger in all dimensions, it’s easily baggable and fits in larger pockets. While it isn’t always pocketable, I haven’t found this to be an issue because the connectivity and app are great, meaning I can quickly check the carbon dioxide concentration even when the device is in my backpack.
The INKBIRD IAM-T1 features a carbon dioxide sensor alongside temperature, relative humidity, and atmospheric pressure sensors. The CO2 sensor is a NDIR sensor from Senseair, whereas the other three sensors are from Sensirion. However, both of these are trusted names within the environmental monitoring space, and I found the NDIR sensor to be accurate in my tests.
While the app for the IAM-T1 is simple, it offers all of the essentials. Here, you can manually calibrate the device or even enable automatic calibration on an eight-day cycle. However, as usual, I don’t recommend automatic calibration unless you are sure your device receives enough exposure to ambient CO2 levels.
Within the app, you can enable the device’s alarm, choose how often it activates, set CO2 level thresholds, and more. The app also allows you to view data for up to one year, and you can quickly export data as a text file if you want to dive deeper into the results. On that note, the device can also hold local data for one month.
The device’s battery life is around four years, with a ten-minute interval on readings. Realistically, however, this interval isn’t very useful, and you’ll want to set the device to a one or two-minute interval. Luckily, even with these settings, the batteries should last many months.
While it is larger than the Aranet4 and Vitalight Mini CO2 Detector, this monitor is my top portable CO2 monitor pick as it’s cheaper than the Aranet with almost the same functionality and is far more feature-packed than the cheaper Vitalight device.
- Can be significantly cheaper than Aranet4
- Offers 95% of Aranet’s functionality
- Great connectivity and app functionality
- NDIR sensor from Senseair is accurate
- Includes temperature, relative humidity, and atmospheric pressure sensors
- Slightly larger than Aranet4 in all dimensions
- High non-sale price
- Automatic calibration might not be ideal without sufficient ambient CO2 exposure
- Battery life decreases with more frequent readings
- Not as portable as some smaller monitors
Best Carbon Dioxide Monitor ($50 – $100)
The SmartAir CO2 Monitor (also called the Qingping CO2 Monitor) is an inexpensive carbon dioxide monitor that has recently changed the game. Before this monitor, you had to spend well over $100 to get a monitor such as the INKBIRD IAM-T1 or Aranet4 Home to have advanced features such as data exporting, app connectivity, and more. However, this monitor has since made all these features far more accessible by significantly lowering the price of such a monitor.
The SmartAir CO2 Monitor is made by Qingping, the company that created the Qingping Air Quality Monitor and Air Quality Monitor Lite. Both of these are fantastic devices, and when I heard that they had released a dedicated carbon dioxide monitor in collaboration with SmartAir, I was very excited.
Luckily, the SmartAir CO2 Monitor hasn’t disappointed. This NDIR-based monitor uses a Sensirion SCD40 – a carbon dioxide sensor that I’ve found to be very accurate in my testing. In fact, this monitor easily keeps up with the Aranet4 Home regarding accuracy.
The SmartAir CO2 Monitor trades blows with the more expensive monitors on this list and has some benefits over the pricier alternatives. However, it also has a few disadvantages and one frustrating downside. This downside is that while the SmartAir CO2 Monitor has both Bluetooth and WiFi, it only sends data via WiFi, meaning the app is useless when you are out and about with the monitor. While the data can store almost 3000 data points locally and will be uploaded to the app as soon the device connects to WiFi again, it’s frustrating that you can’t use the app while on the move.
On the flip side, the SmartAir CO2 Monitor relies on an internal battery with a 6-30 day battery life (depending on your CO2 measurement and uploading intervals). I love having an internal battery with good battery life, as it means I don’t need to ensure I always have AA batteries on hand. If you have the Aranet4 Home set to record every minute, you’ll need new AA batteries every few months, and the cost can quickly add up.
Since the SmartAir CO2 Monitor uses the Qingping ecosystem, you can use the Qingping IoT app to view data from not only this monitor but any other Qingping monitors you have. If you already have a Qingping Air Quality Monitor or Air Quality Monitor Lite, this alone might be enough of an incentive to purchase the SmartAir CO2 Monitor!
- Inexpensive and accessible
- Accurate NDIR sensor (Sensirion SCD40)
- Internal battery with 6-30 day battery life
- Data exporting and app connectivity
- Integration with Qingping IoT app for unified data viewing
- App connectivity limited to WiFi only
- App is unusable when out of WiFi range
- Limited local data storage (3000 data points)
Best Carbon Dioxide Monitor (Less than $50)
Prefer video? Watch my YouTube review here.
The Vitalight Mini CO2 Detector is a very affordable carbon dioxide monitor costing only $40- $50. While the monitor does have flaws, the exceptionally low price for an NDIR-equipped monitor makes it a very appealing device worth considering.
The Vitalight Mini CO2 Detector is a small, minimal device. Looking around the device, you’ll find only a few intake vents, a USB-C charging port, a single button, and a small screen. There is no connectivity, relative humidity, temperature sensing, or other frills. It’s a simple device designed to monitor the carbon dioxide concentration at any time – nothing more, nothing less.
Besides the affordable price, the Vitalight Mini CO2 Detector’s biggest benefits are the USB-C-powered battery and exceptional portability. Unfortunately, these benefits come alongside a few flaws.
Firstly, the battery life is quite short, at only eight hours. While this will allow you to use the device throughout the day at work or school, it’s a frustrating disadvantage of the device. I hate having so many devices to charge, and the Vitalight Mini CO2 detector is yet another device requiring daily charging.
Secondly, and more importantly, the device has an auto-calibration feature, which can render the device inaccurate if you don’t know how to account for this ‘feature’. In my full review, I discuss how you can avoid the issues caused by auto-calibration, and I recommend reading that article before purchasing a Vitalight.
However, if you can manage the auto-calibration feature, the device is surprisingly accurate – especially considering the price. I often find the Vitalight reading very similar (or identically) to far more expensive monitors such as the Aranet4.
- Very affordable ($40-$50)
- NDIR-equipped for accurate CO2 readings
- USB-C-powered battery
- Exceptional portability
- Simple and minimal design
- Short battery life (only eight hours)
- No connectivity or additional sensors (relative humidity, temperature, etc.)
- Auto-calibration can cause inaccuracies
- Requires daily charging
Best All-in-One Carbon Dioxide Monitor ($100+)
Suppose you want an indoor carbon dioxide monitor that also happens to monitor a large range of other indoor air pollutants. In that case, the AirGradient ONE might be exactly what you’re looking for. This monitor uses a Senseair S8 sensor, which is proven to be an accurate CO2 sensor that provides reliable results. However, it has a built-in auto-calibration feature, meaning you will want to monitor its readings to ensure it isn’t losing accuracy. Luckily, manual calibration is also supported.
What makes the AirGradient ONE so compelling is the pricing. Compared to other monitors that feature the range of sensors you’ll find in this device, you’re generally looking at $200-$400. However, the AirGradient ONE comes in at only $138 – provided you’re willing to build the monitor yourself. Before you say, ‘I can’t possibly do that!’, don’t worry – it’s an incredibly easy process that takes only 10 minutes.
No soldering is required; all you need to do is slot the included components into their slots. Of course, instructions are provided. I recently got this kit, and I was amazed at how easy it was to assemble the monitor – really, it’s an exceptionally easy process. However, if you don’t want to DIY, you can purchase a pre-built kit for $195. While this is still a fantastic deal, it’s not quite as amazing as buying such a high-quality monitor for less than $150.
The AirGradient ONE connects via WiFi and uploads data to a web dashboard. This dashboard will allow you to view current and historical data from the device, and it also allows you to customise the LEDs on the device to adjust their thresholds or the pollutants they represent. While there is no smartphone app, the web dashboard is powerful, and I haven’t found it to be lacking.
This device doesn’t have an internal battery, so it must always be powered. That said, it’s perfect if you need a monitor for your home or office. I also imagine that this monitor would excel in classrooms and small businesses that want to monitor CO2 and other indoor pollutants to improve productivity.
Overall, the AirGradient ONE is a fantastic indoor carbon dioxide monitor that will also allow you to track other potentially harmful indoor air pollutants. With both DIY and assembled kits available, this device has a lot of flexibility. Oh, and I forgot the best part – each component is user-replaceable, and both the hardware and software are open-source.
- Affordable price ($138 for DIY kit)
- Uses accurate Senseair S8 CO2 sensor
- Easy assembly process with no soldering required
- Manual calibration supported
- User-replaceable components and open-source hardware/software
- Built-in auto-calibration may affect accuracy (but can be disabled)
- No internal battery, must always be powered
- No smartphone app, only web dashboard
- Pre-built kit is more expensive ($195)
Best All-in-One Carbon Dioxide Monitor (Less than $100)
The Qingping Air Monitor’s little brother, the Qingping Air Monitor Lite (they could find a better naming scheme), is also a great choice for a more complete indoor air quality monitor. While the monitor features a carbon dioxide sensor, it is also accompanied by a PM2.5, PM10, relative humidity, and temperature sensor. For such a little package, it’s very complete!
Like its bigger sibling, the Qingping Air Monitor Lite is not intended to be portable. While it houses a similar-length eight-hour battery, and its form factor is perfect for a portable device, it isn’t intended to be used on the go. For one, the battery life is a bit too short, and furthermore, you have to wait about five minutes after turning the device on to get an accurate reading. Not great while out and about!
The Qingping Air Monitor Lite is a great choice as a desk-based carbon dioxide monitor. The larger Air Monitor feels cluttered and overwhelming, but the small Air Monitor Lite is exceptionally simple. You can set the screen to show a single reading (these can be scrolled between), and that’s all that is displayed on the screen.
Now, this does make the device a bit too simple. You’ll find yourself scrolling through all the sensor readings to get a full overview of your indoor air quality. Since you need to scroll through the CO2, PM2.5, PM10, temperature and relative humidity readings, this can take a good 10 seconds.
If you can manage this small inconvenience, the Qingping Air Monitor Lite has an accurate, albeit conservative, carbon dioxide sensor. Even after manually calibrating the device (which is possible!) I found it to record readings about 100ppm lower than my other devices.
In reality, though, this isn’t much of an issue. At the end of the day, whether you’re seeing 1400ppm or 1500ppm, both indicate that better ventilation is needed. Therefore, this discrepancy in readings is minor enough to be overlooked.
The Qingping+ App can also be used with the Air Monitor Lite, allowing the user to change basic settings and see historical data. While the data viewing is limited to 15-minute intervals in the 24-hour view and 1-day intervals in the 30-day view, the ability to view and export data is a nice addition.
The Qingping Air Monitor Lite also supports Apple Homekit, so if you’re an Apple user, you’ll be able to integrate this little air quality monitor into your smart home. Even though I use an iPhone, I found myself using the Qingping+ app more often as it provides more data.
- Complete set of sensors (CO2, PM2.5, PM10, relative humidity, temperature)
- Simple and uncluttered interface
- Manual calibration possible
- Integration with Qingping+ App and Apple HomeKit
- Data viewing and exporting available
- Not intended to be portable
- Short battery life (eight hours)
- Takes five minutes to provide accurate readings after power on
- Need to scroll through multiple readings to get a full overview
- Carbon dioxide readings are conservative (often reads lower than other monitors)
Best Small Carbon Dioxide Monitor
If you want the smallest and most inconspicuous carbon dioxide monitor out there, the AIRVALENT monitor is your best choice. While it might not look like it at first glance, this monitor is half the size of the Aranet4 Home, and even the Vitalight Mini CO2 Detector looks massive next to it. Combined with the approachable way this monitor shows information, it’s a great device for people who don’t want and would prefer that their CO2 monitor goes unnoticed.
The AIRVALENT carbon dioxide monitor uses a Sensirion SCD41 photoacoustic NDIR sensor. While this sensor is very accurate at room temperatures (less than 30 degrees Celsius), I did find that it began to read quite inaccurately when the temperature was between 30 and 40 degrees. That said, I don’t see this as an issue for most users, as this device will primarily be used indoors. The SCD41 performs very well in these conditions, and I’ve found it accurate in my testing.
While the AIRVALENT CO2 monitor can be used as a standalone device, you will want to use Bluetooth and the accompanying app on your smartphone to get the most out of it. The app allows you to change the settings and view historical data from the monitor. It also allows you to change the device’s display with various layouts and designs. This is a unique feature among CO2 monitors, and I love having a little customisation available.
Battery life is a common concern with such a small monitor. However, the AIRVALENT monitor performs surprisingly well in this regard, and it has between five and 30 days of battery life, depending on the measurement interval you set (one to fifteen minutes). Personally, I set my monitor to take readings every minute, and I’ve found the claimed five days of battery life to be about right.
The biggest downside of this monitor is the price. While, technically, the Aranet4 is more expensive at its normal price, it’s often on sale and can be found for less than this monitor. Though it does perform well, this makes it a tough sell as the Aranet has a stellar reputation. That said, there are some significant advantages with this monitor, too.
If you’re looking for a compact carbon dioxide monitor that you don’t need to worry about charging every night, the AIRVALENT CO2 monitor is not only a great choice, but it’s really your only choice. This monitor is perfect for giving to children to take to school, too, as it’s compact and straightforward. With the range of easy-to-understand displays you can alternate between, it’s really the perfect choice for anyone looking for a simple-to-use monitor that has advanced functionality.
- Small and inconspicuous design
- Uses accurate Sensirion SCD41 photoacoustic NDIR sensor
- Customizable display options via the app
- Battery life between five and 30 days depending on settings
- Great for children to take to school due to its compact and straightforward design
- High price compared to other monitors like the Aranet4
- Accuracy issues at temperatures above 30 degrees Celsius
- Doesn’t have an instant measurement feature
Best Ultra-Small Carbon Dioxide Monitor
The AirSpot carbon dioxide monitor is currently (at least, to my knowledge) the smallest carbon dioxide monitor that I would consider an ‘all-in-one’ device. That is to say, it includes a carbon dioxide sensor, battery, screen, and connectivity. If you want a carbon dioxide sensor alone, finding smaller devices is possible. However, out of the all-in-one monitors, this is the smallest – by a significant margin.
The AirSpot monitor is incredibly small and weighs less than 20 grams, meaning it’s almost weightless as soon as you place it in your pocket or handbag. This, combined with the fact that some accessories are available for the AirSpot monitor, makes it the most convenient carbon dioxide monitor currently out there. What are the accessories exactly? Good question! Not only can you get a keychain accessory that allows you to attach this device to a keychain or backpack easily, but a watch strap is also available! Combined with the size and weight of this device, it’s easy to see why this monitor is so handy.
Similar to many other monitors on this list, the AirSpot monitor uses a Sensirion SCD41 photoacoustic CO2 sensor. This sensor is well-regarded due to its high accuracy and extremely small size. While traditional NDIR sensors are still a bit better, in my opinion, due to the fact they aren’t impacted by sound, this is a good sensor and one that provides good (and reliable) readings.
The AirSpot monitor connects to a smartphone via Bluetooth, and depending on the reading interval you set, the battery life varies from around 12 hours to as long as three weeks. If you prefer, you can even disable automatic readings (so the device only takes a measurement when you press the button) to really conserve battery life. I appreciate having these settings, as they allow the user to adjust the device to their preferences.
These adjustment options expand to other parts of the app, too, and it’s a very powerful application overall. Out of the carbon dioxide monitors that I’ve tried, I found this application to have the widest range of customisation settings, meaning that users can customise this device exactly how they want to. There is also a lot of information built into the app, meaning it’s a good platform for anyone wanting to learn more about air quality and its implications.
The biggest downside I found with the AirSpot carbon dioxide monitor is the build quality, which, while not bad, I found to feel a bit cheap due to the predominantly plastic build. While this is likely how they were able to make the device so light, it does mean the device doesn’t feel as nice as some other monitors on this list. With that said, I’ve found it to be quite durable so far, so this is likely a non-issue for most users.
- Ultra-compact design and weight
- Uses accurate Sensirion SCD41 photoacoustic NDIR sensor
- Very detailed app with many settings
- Battery life between 12 hours and 21 days depending on settings
- Has a range of accesories that can be used with the monitor
- Feels somewhat cheap due to being primarily plastic
- Can be challenging to calibrate
- App can seem complicated at first
Best Connected Carbon Dioxide Monitor
CO2 Click offers two models of this monitor – the connected Model C and the standalone Model D. The price difference between the two is 10 CAD, and I recommend the Model C to everyone. While the Model D is a great monitor, the connectivity of the Model C is invaluable.
Both Model C and Model D use a top-of-the-line Sensirion SCD30 sensor, which provides the same accuracy level as the significantly more expensive Aranet4 Home. This carbon dioxide monitor also includes temperature and relative humidity sensors.
While the CO2 Click Model C includes a built-in battery, battery life is short at around eight hours. This is competitive with the Qingping carbon dioxide monitors and the Vitalight but also falls far short of the Aranet4. For this reason, I would recommend the Aranet4 as a portable monitor if you can afford it.
With that said the Model C is a fantastic choice for a home, office, classroom, or store monitor. It’s small and unobtrusive, well-connected, and the data can easily be shared via a QR code. The best part? You can add multiple monitors to the WiFi dashboard and track them all in one place.
Despite being relatively affordable, the CO2 Click Model C features high-end hardware and advanced features. The dual-beam NDIR sensor makes this the only dual-beam device on this list, and the device sports no auto-calibration (which is a big advantage). On top of this, Model C supports data exporting (with notes), adjustable reading intervals, and even allows you to set the CO2 offset.
The biggest downside with CO2 Click devices is the build quality. While it is by no means bad, the 3D printing of the device isn’t quite up to par with other devices on this list – perhaps except for the Vitalight Mini CO2 Detector, which feels cheap.
However, besides this, I struggled to find downsides to CO2 Click Model C. It’s a fully capable monitor with tons of features and great accuracy. What makes it even more compelling, though, is the price. While it’s far from the cheapest monitor on this list, what you get for the price makes it a great choice for anyone looking for a mostly static indoor carbon dioxide monitor that can be portable when needed.
- Uses top-of-the-line Sensirion SCD30 sensor
- Includes temperature and relative humidity sensors
- Model C offers connectivity for data sharing and tracking
- Supports multiple monitors on one WiFi dashboard
- Advanced features like data exporting, adjustable intervals, and CO2 offset
- Short battery life (around eight hours)
- Build quality not up to par with other devices
- 3D printing of the device could be improved
- Not as portable as some other monitors (e.g., Aranet4)
Best Desk-Based Air Pollution Monitor
If you want a carbon dioxide monitor that provides greater insight into your indoor air quality, the Qingping Air Monitor Gen 2 (or even the previous generation 1) might be the device for you. This indoor air quality monitor features a CO2 sensor alongside PM10, tVOC, relative humidity, and temperature sensors. In other words, it’s the most complete indoor air quality monitor on this list.
The Qingping Air Monitor is intended to be used as a tabletop or shelf monitor. While it has a small internal battery, its life is short, and you’ll be lucky to get eight hours from it. Furthermore, the product’s design shows that it isn’t portable – I would worry about it breaking in my backpack.
However, the Qingping Air Monitor excels at being a not-so-portable indoor air quality monitor. With a responsive touch screen, a great accompanying app, and a high-resolution (albeit cluttered) display, there isn’t much to wish for on the Qingping Air Monitor. Considering its feature set, it’s also affordably priced!
In my testing, I found the carbon dioxide sensor in the Air Monitor to be quite accurate compared to other carbon dioxide monitors. While the readings were a bit conservative, the CO2 monitor features a recalibration feature that allows users to manually recalibrate the sensor.
Testing done by SmartAir has also shown the PM2.5 sensor to be accurate. However, the tVOC sensor does have a larger margin of error, with the sensor only offering accuracy within 20% of the actual tVOC concentration. The good news? This is more than accurate enough to identify overall trends in your air quality and act accordingly.
On the Qingping+ App (the app which you’ll want to download to get the most out of the monitor), you can view historical data and change the measurement units of the device. While the app is otherwise quite sparse, it’s straightforward to use, and I never had any issues with lag or crashing.
That said, a few changes would improve the Qingping Air Monitor. Firstly, the app needs to support more time brackets in its graphs. Secondly, and more importantly, the display can be quite cluttered – I would like to see a feature allowing the user to display only the pollutant they are interested in.
Regardless, these issues are far from deal-breakers. This is a fantastic choice if you want a device that you can glance at to get an overview of your indoor air quality. If you’re looking for something smaller, simpler, or cheaper, you might want to check the smaller Qingping monitor, the Qingping Air Monitor Lite.
- Complete set of sensors (CO2, PM10, tVOC, relative humidity, temperature)
- Responsive touch screen and high-resolution display
- Great accompanying app (Qingping+)
- Manual recalibration feature for CO2 sensor
- Affordably priced considering the feature set
- Short battery life (around eight hours)
- Not portable, fragile design
- Cluttered display
- tVOC sensor accuracy within 20%
- App lacks support for more time brackets in graphs
Best Standalone Carbon Dioxide Monitor
While most monitors on this list advertise their connectivity as a feature, there are times when a simple monitor rules. While I’m an edge case, as a reviewer, I often have over ten monitor apps on my phone. While this is a bit excessive, I can’t lie – I hate it! I would far prefer to have a minimalist phone with as few apps as I can manage. I know I’m not the only one in this camp, and I also know that many people have other reasons for wanting a carbon dioxide monitor that doesn’t need a regular connection to your smartphone.
That’s where the CO2 Click Model F comes in. This is the ‘affordable’ offering from CO2 Click, and while it’s not exactly cheap, it is on the more affordable end of monitors on this list. The monitor manages this price point by dropping connectivity and other advanced features, but it still manages to fit a fantastic sensor into the small, bubblegum-shaped housing.
Like the AIRVALENT and SmartAir monitors, the Model F uses Sensirion’s SCD41 photoacoustic NDIR sensor. While this sensor has some caveats compared to traditional NDIR sensors, it’s a great sensor for most users and, most importantly, accurate. It’s also important to note that the SCD41 is absolutely tiny, which is why it’s the most popular sensor for these ultra-small CO2 monitors.
As mentioned, the CO2 Click Model F is a good standalone monitor because it’s small, has enough battery life to last one day, and is quite light. I found the size much more pocketable than other devices like the Aranet4 and even the AIRVALENT monitor just because it’s convenient. Of course, having a monitor with no connectivity does bring many limitations, which is why this monitor has connectivity – but it’s not something you will use often.
The device can create a WiFi hotspot to connect to your phone. From there, you are able to calibrate the device, download data from the past three days, and also set some basic settings such as date and time. Overall, the settings are super simple, and you really won’t find yourself using this connectivity often unless you want to calibrate the monitor or export data. For this reason, I still consider this a ‘standalone’ monitor.
As with all CO2 Click products, the Model F is 3D printed, meaning that the build quality can lag behind that of larger manufacturers. That said, I’ve never found this to be an issue, and I am happy to take my Model F wherever I go. There is also a frustrating issue where the date and time are lost every time the battery goes flat, though, and I hope this will be remedied in time.
- Compact and portable design
- Uses accurate Sensirion SCD41 photoacoustic NDIR sensor
- Standalone monitor (no need for connectivity)
- Affordable compared to premium monitors
- Simple and straightforward calibration process
- No web dashboard or app for remote monitoring
- Lack of atmospheric pressure sensor affects accuracy at high altitudes
- Short battery life of around 15 hours
Carbon Dioxide Monitor FAQ
Do I Need a Carbon Dioxide Monitor?
Probably not. However, a carbon dioxide monitor is a great way to monitor ventilation and having one can allow you to take action regarding ventilation and masking.
How Much Are Carbon Dioxide Monitors?
Consumer-grade carbon dioxide monitors start at around $50 and can sell for as much as $300.
What Do I Need in a Carbon Dioxide Monitor?
You’ll want to ensure the carbon dioxide monitor has an NDIR sensor, allows for manual calibration, and has a battery (if you want to use it on the go).
What’s the Best Carbon Dioxide Monitor?
It depends on your needs. The Vitalight Mini CO2 Detector is the most portable, but the Aranet4 is the most accurate.
What’s a Good Carbon Dioxide Concentration?
Whenever possible, you’ll want to stay below 800ppm. If this isn’t possible, under 1000ppm is generally considered safe.
Have Questions or Comments?
Join the discussion on the BreatheSafeAir Community Forum. Ask any questions you have about air quality or adjacent topics and get quick answers!
If you want to learn more about affordable carbon dioxide monitors specifically, please check out this post!
I’ve just updated this article to include the AirSpot CO2 monitor (full review here: AirSpot Review - A Tiny Carbon Dioxide Monitor That Can Be Worn as a Watch!) as I believe this monitor deserves a place here!
I also added mention of both the AIRVALENT TravelLite and Livegrid - two more devices worth noting!