Carbon Dioxide Monitors – What You Need to Know + 6 Best Monitors

Despite being around for many years, carbon dioxide monitors have only begun to take off recently. The monitors – ideal for identifying poor indoor air ventilation – have since become commonplace in thousands of individuals’ pockets, backpacks, homes, and offices worldwide.

However, there are now so many carbon dioxide monitor choices on the market that it’s become difficult to make the correct purchasing decision. Which monitors are portable? Which monitors have accompanying apps? And, above all, which monitors are accurately measuring the carbon dioxide concentration?

In this article, I will tell you what I believe the best carbon dioxide monitors for each situation are. I’ve only included monitors in this list that I have first-hand experience with. This means that while this list isn’t exhaustive, it includes many of the most popular consumer-grade carbon dioxide monitors. I chose not to include monitors I haven’t experienced because I believe it’s disingenuous to recommend something I haven’t tried.

Now, I mentioned consumer grade in the above paragraph. This is because this article is aimed entirely at users looking to pick up a consumer-level monitor. If you’re a working professional needing a carbon dioxide monitor, you’ll want to check out a NIST-calibrated device such as those offered by Forensics Detectors.

If you’re looking for something a bit less specialist-orientated, such as a monitor to identify poor ventilation, viral transmission chance, or the cognitive impact of carbon dioxide, then you’re in the right place. 

As always, I am open to suggestions for monitors to include on this list. If you know of a carbon dioxide monitor I’ve overlooked, please let me know in the comments below. I am constantly expanding this list, and I would love to know what you want to see included. Now, with that out of the way, let’s get started!

This post contains affiliate links. For more information, please refer to my affiliate disclaimer. 

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 information and information is subject to change without notice.

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 evidence showing how harmful carbon dioxide can be – even in common indoor concentrations – there is now ample evidence showing why it’s essential to monitor the gas.

Recently, carbon dioxide monitoring has gained a lot of attention as it’s been found that carbon dioxide levels can be a proxy for the transmission chance of COVID. That is to say when in a public space (or anywhere with other people present), high carbon dioxide levels can indicate the COVID-19 risk.

Of course, while COVID-19 is fairly getting all the current media attention, the use of carbon dioxide monitors isn’t limited to this virus alone. Since carbon dioxide levels reflect ventilation, these monitors can also show the transmission chance of other airborne pathogens. 

Therefore, one great reason to use carbon dioxide monitors is to identify poor indoor ventilation and act on it. This can let you know when it’s a good idea to don your favourite disposable mask in public spaces.

However, while COVID-19 has massively boosted the popularity of monitoring carbon dioxide, it’s far from the only reason to keep a close eye on the gas. I would even argue this isn’t the primary reason to monitor carbon dioxide.

That’s because carbon dioxide has a large range of impacts on its own. It’s been tied to drowsiness, poor sleep quality, decreased cognitive performance, and more. Although these may seem minor, they’re anything but that.

A Harvard study found that at only 1400ppm (parts per million), our cognitive performance is decreased by 50%. 1400ppm is far from a high concentration – if you’re sitting in a bedroom, on a bus, or in a cafe with poor ventilation while reading this, you’re probably experiencing this cognitive decline.

The same study also found that at 950ppm – an even more common carbon dioxide concentration – our cognitive performance declines by around 15%. This means that your brain is slowed down anytime you are in a poorly ventilated indoor environment.

Furthermore, excess indoor carbon dioxide concentrations have been found to lead to stress, kidney calcification, and bone demineralisation – all serious conditions avoidable with good ventilation.

The impacts of carbon dioxide go deeper than this; however, we still have a lot of research to do in the field. Only recently was indoor carbon dioxide identified as something we should be worried about, and it’s even more recent that the media began reporting on it.

With that said, even with more findings constantly coming to light, we already know that monitoring carbon dioxide is critical. Not only can having a carbon dioxide monitor indicate the transmission chance of airborne pathogens, but they allow us to know when ventilation is necessary. Without this information available, you’re likely performing sub-optimally.

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 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

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, recently, photoacoustic sensors have been gaining some attention. These sensors cost around the same as NDIR sensors and are similarly accurate. Therefore, products using photoacoustic technology could be worth checking out too. That said, NDIR is far more common, and most carbon dioxide monitors rely on these tried and tested sensors.

Manual Recalibration

A lack of recalibration can lead to skewed readings.

While NDIR sensors are accurate, they do suffer some issues. One of these issues is sensor drift. Over time, it’s possible (and very likely) your carbon dioxide monitor will start to provide skewed measurements. This is called sensor drift and can be caused by a range of variables.

Since sensor drift can impact any consumer-grade carbon dioxide monitor, it’s important to have a way to counter this passive drift. The best way to do this is to manually recalibrate your device from time to time.

The recalibration process is normally quite straightforward and involves taking your carbon dioxide monitor outside for a few minutes. This gives the monitor time to create a new baseline from the atmospheric carbon dioxide (normally around 420ppm, but it can vary).

Since every carbon dioxide monitor is susceptible to sensor drift, purchasing a carbon dioxide monitor that allows for manual calibration is important. While some devices offer auto calibration as a ‘feature’, this can cause issues when the device isn’t taken outside for long periods of time (to create a new baseline value).

Single-Beam vs Dual-Beam NDIR

Dual-beam NDIR. Image source.

Within NDIR, there are two sensor types – single-beam and dual-beam. Both of these sensor types operate in exactly the same fashion, and both have the same potential for accuracy. The difference, however, is that dual-beam NDIR sensors have a second reference beam normally used once daily.

This second beam is typically factory set and is used to automatically calibrate the primary sensor, which is constantly being used and can have more drift. In theory, this allows the device to remain more accurate without manual calibrations.

Senseair (a big sensor company which makes both single-beam and dual-beam NDIR sensors) states that dual-beam NDIR is not particularly effective in the long term. While dual-beam products may be more accurate out of the box (close to their factory calibration), many variables can cause readings to drift – even on dual-beam sensors.

Therefore, while some companies will heavily advertise their usage of a dual-beam sensor, it’s far from an essential feature. Over time, both single-beam and dual-beam NDIR will require calibrating and be similarly accurate. The one advantage of dual beam NDIR is that your monitor should be accurate without user input while it’s new.

Historical Data

Left: Qingping historical view. Right: Aranet4 historical view.

You can view and analyse data on most carbon dioxide monitors in two ways. The first is on the device itself. However, this has some big downsides – specifically, you can only get information on carbon dioxide concentrations at the given moment. There is no way to view historical data.

Some higher-end devices fix this issue by allowing the user to view data on an app or export it in a spreadsheet. This is incredibly useful as it can allow you to identify ventilation trends and compare data from different time periods. Want to know if the carbon dioxide concentrations increase while you’re sleeping? This is data you won’t be able to see on a monitor unless it supports a historical data view.

Some people will consider this feature unnecessary, but I highly recommend purchasing a monitor with such a feature if you can afford it. On this list, devices such as the Aranet4 and Qingping monitors support data exporting and viewing via an app.

Other Sensors

Sensors and accuracy on the Aranet4.

Most carbon dioxide monitors feature more than just a carbon dioxide sensor. Nearly every monitor on this list also has a relative humidity and temperature sensor, and while these aren’t necessary, they are nice additions to have. While carbon dioxide is a good indicator of when ventilation is needed, seeing the humidity and temperature provides deeper insight into overall air quality.

Some devices on this list offer more complete sensor arranges, with PM2.5, PM10, tVOC and atmospheric pressure sensors. While these are unnecessary on a carbon dioxide monitor, they are great on indoor air quality monitors.

When purchasing a carbon dioxide monitor, you’ll want to ask yourself, ‘do I need these extra sensors, or could I find them beneficial?’. If the answer is yes, you’ll want to look at a device which includes them.

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 wildly. Some monitors will have only a couple of hours of battery life (or none!), while some can last as long as four years! To say there is a crazy level of variation in battery life might be an understatement!

When deciding which carbon dioxide monitor best suits your needs, you’ll want to keep battery life in mind. If you are looking for a desk-based solution to be used at home, you won’t need a device with long battery life. On the other hand, if you want a portable monitor to take everywhere, you’ll want to look for the longest battery life possible.

You’ll also want to consider how the device is powered. Does it require AA batteries? Is it USB-rechargeable? If so, what kind of connection does it use? Although many people are indifferent, some will prefer to have a USB Type-C compatible device.

Best Carbon Dioxide Monitors

Best Premium Carbon Dioxide Monitor

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. While I’m not a fan of the price hike – $250 is 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? Well, it has incredible battery life (as long as four years!), a highly accurate NDIR sensor, a fantastic accompanying app, and is super easily pocketable. 

Alongside the carbon dioxide sensor, you’ll also find a relative humidity, temperature, and atmospheric pressure sensor. These sensors can be used to monitor the environment or discover relationships between carbon dioxide and other variables. Combined, these features, sensors, and more make the Aranet4 a solid offering.

What about the downsides? Well, the most obvious downside is the price. The Aranet4 is the most expensive carbon dioxide monitor on this list; for many, the price isn’t justifiable. On top of that, the device can only use AA batteries – there’s no internal, rechargeable battery.

Overall, however, it’s hard to find disadvantages to the Aranet4 other than the price. The device is great 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!

Purchase Aranet4 Home | Read my full Aranet4 review

Best Connected Carbon Dioxide Monitor

CO2.Click offers two models – 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 CO2.Click monitors use a top-of-the-line Sensirion SCD30 sensor that provides the same accuracy level as the significantly more expensive Aranet4 Home. Also included in this carbon dioxide monitor are 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 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. 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.

Purchase CO2.Click Model C | Read my full CO2.Click review

Best Affordable Carbon Dioxide Monitor

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 biggest benefits of the Vitalight Mini CO2 Detector are the USB-C powered battery and the exceptional portability of the device. 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. Oftentimes I find the Vitalight reading very similarly (or identically) to far more expensive monitors such as the Aranet4.

Purchase Vitalight Mini CO2 Detector | Read my full Vitalight Mini CO2 Detector review

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 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 when needed.

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.

Purchase Qingping Air Monitor | Purchase from SmartAir | Read my full Qingping Air Monitor Review

Best Desk-Based Carbon Dioxide Monitor

If you’re looking for a desk-based carbon dioxide monitor but don’t need all the extra sensors the Qingping Air Monitor includes, you might want to check out the Forensics Detectors Carbon Dioxide Monitor. This monitor is available in two options – one which is powered by a micro USB cable and one with a power plug built into the back of the device.

The Forensics Detectors Carbon Dioxide Monitor includes an internal battery with eight hours of battery life per the official specifications. However, I found the battery to last 18-24 hours regularly. However, despite this longer battery life, the device is not portable – it’s just too large and designed to sit on a desk, table, or windowsill.

In my testing, I found this carbon dioxide monitor to provide almost identical readings to the Aranet4. This means the Forensics Detectors Carbon Dioxide Monitor is accurate, and I am confident in the readings provided by the monitor. Furthermore, it has no auto-calibration ‘feature’ to skew readings.

Instead, this carbon dioxide monitor relies entirely on manual calibrations, which should be performed every few months. While this might sound like a hassle, I appreciate the lack of auto-calibration, as periodic calibrations often cause more trouble in the long run as readings become increasingly inaccurate.

While the Forensics Detectors Carbon Dioxide Monitor is an accurate, affordable device, it isn’t perfect. the screen is not great, and I wish they would replace it with an E-ink screen similar to many other carbon dioxide monitors. Furthermore, there is no way to export or view the device’s historical data.

Therefore, you will want to look elsewhere if you need a device with data logging. However, the Forensics Detectors Carbon Dioxide Monitor is a good choice if you’re looking for a simple device with no connectivity. It’s a no-frills device with no unnecessary complications. Instead, it focuses on providing accurate insights into carbon dioxide concentrations at the current time.

Further leaning into this carbon dioxide monitor’s simplicity is its lack of a companion app or connectivity. Some people will appreciate this – it is set and forget. However, for power-users, this monitor may lack some features you consider essential.

Purchase Forensics Detectors Carbon Dioxide Monitor | Read my full Forensics Detectors Carbon Dioxide Monitor Review

Best All-in-One Carbon Dioxide Monitor

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, this 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.

Purchase Qingping Air Monitor Lite | Purchase from SmartAir | Read my full Qingping Air Monitor Lite Review

Carbon Dioxide Monitor FAQ