Recently, carbon dioxide monitors have been gaining a lot of attention. With findings showing how detrimental CO2 is to our cognitive performance and drowsiness levels, it’s no wonder that more people are beginning to show an interest in monitoring the carbon dioxide concentrations in their local environment.
However, it was only the more recent finding that carbon dioxide concentrations act as a proxy for the risk of catching COVID-19 that carbon dioxide monitors began to take off. With no accurate way to determine the number of COVID-19 particles in the air, the ability to monitor carbon dioxide is the next best alternative – but more on that soon!
Due to these findings, carbon dioxide monitors have recently gained popularity. While schools and offices have been turning to wall-mounted and desk-based solutions, consumers have turned to portable carbon dioxide monitors. Among the current devices on the market, the most well-known and most reputable device is the Aranet4.
The Aranet4 is a hand-held carbon dioxide monitor about half the length of a small smartphone. Although about twice the thickness, the device is easily pocketable – even alongside a wallet and earbuds. On the front of the device is an e-ink screen featuring a few simple readings. Most notably is the large CO2 PPM reading that dominates the centre of the screen.
All this is to say; the Aranet4 is a simple device with one feature – to monitor carbon dioxide levels and quickly and effectively communicate them with the user. However, the technology behind the device is very complex, and there are few accurate carbon dioxide monitors on the market. The Aranet4 is one of the few accurate devices.
The team at Aranet was kind enough to send me an Aranet4 Home for review. Over the past month, I’ve used the device extensively. I’ve travelled with the monitor, taking it on planes, buses, and into malls. I’ve also used it at home and during walks in the park to test the accuracy of the readings against atmospheric air.
After using the device in various settings, I am happy to share my full review of the Aranet4 finally. This review will examine the device’s accuracy, usability, and price. However, I first want to address the elephant in the room – is a CO2 monitor even necessary and who can use such a device?
Note: the Aranet4 comes in two variants – the Aranet4 Home and Aranet4 PRO. Both devices are the exact same in terms of accuracy, design, and user experience. However, the key difference is that the Aranet4 Home is designed to be used as a standalone device. Aranet4 PRO is designed to be part of a network including multiple Aranet4 PROs and an Aranet PRO Base Station. View the differences here.
This post contains affiliate links. For more information, please refer to my affiliate disclaimer. I was sent a product for review, but the article is not sponsored. All opinions expressed in this post are my honest thoughts. I only recommend products that I genuinely 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, and information is subject to change without notice. Devices mentioned on this website are not medical devices and do not guarantee protection.
Do I Need a Carbon Dioxide Monitor?
If you’re an air quality enthusiast and already know the importance of a carbon dioxide monitor, feel free to skip this section. However, since I foresee many people asking this, I want to address the topic before starting my review.
Carbon dioxide is a prevalent gas, and it’s something that surrounds us. However, while we hear about the impacts of carbon dioxide in the atmosphere almost every week, we rarely hear about the microscale impacts of carbon dioxide. Considering we live in an atmosphere including carbon dioxide, surely it can’t harm us?
Well, yes and no. The concentrations of carbon dioxide we are usually exposed to are unlikely to course long-term damage. For that to occur, we must be exposed to quite severe concentrations of carbon dioxide for a long time.
However, carbon dioxide does significantly impact us in the short term. A Havard study found that at 1400ppm (parts per million), our cognitive function decreases by 50%. 1400ppm isn’t incredibly high, and this is a concentration you can regularly find in indoor areas, including schools, offices, and homes.
Excess carbon dioxide levels can also cause drowsiness, headaches, and many other issues – none conducive to good health. Since we tend not to consider carbon dioxide levels, we rarely consider how they can impact us – however, they can affect us significantly.
While carbon dioxide alone significantly alters how we think, it wasn’t until the COVID-19 pandemic that carbon dioxide monitors began to take off. This is because while we currently have no device to monitor the airborne COVID-19 particles in a given area, we can monitor the carbon dioxide.
Carbon dioxide concentrations act as a proxy for the risk of COVID-19 transmission. Assuming you are in a public space, a doubling in carbon dioxide concentrations indicates twice the chance of contracting COVID-19. For example, on a bus with 800ppm, you have twice the chance of catching COVID-19 compared to ambient levels (just over 400ppm).
This proxy risk caused a massive boom in the popularity of handheld carbon dioxide monitors such as the Aranet4 Home. However, it’s far from the only reason to have a carbon dioxide monitor as the gas has a range of adverse health impacts that are important to avoid.
A carbon dioxide monitor will allow you to see into a world that you otherwise can’t. It will allow you to know when this invisible gas is changing how you feel and when better ventilation is needed. Even further, if you want to use it as a portable device, it will let you see the COVID-19 (and other airborne viruses) risk at any given moment.
Carbon dioxide monitors are a relatively niche device; not everyone needs one. However, after using the device for a few weeks, I found it incredibly useful. Not only have I learnt where high-risk areas are and where I should be donning my mask (for COVID-19), but I’ve also learnt what rooms in my house need more ventilation and have been able to improve the air quality in them.
As a final note, I had a friend who lived in a small apartment who complained about constantly feeling tired at home. I mentioned it could be carbon dioxide and recommended he open the windows regularly to see if it would help. A few days later, he returned to me and said it was life-changing – he felt far fresher and more awake than he had at home in months.
Monitoring carbon dioxide levels and acting on the information is incredibly beneficial. Like indoor air pollution monitors, which monitor the particulate matter and VOCs, I recommend a portable device such as the Aranet4 Home for anyone wanting to improve the quality of the air they breathe. It really can change how you live and especially how you feel.
Accuracy
Perhaps the most critical question regarding CO2 monitors is ‘what is the accuracy?’. Accuracy is the most significant difference between cheap and pricier alternatives within this space – it’s also what drives the price of the Aranet4 Home up.
When it comes to CO2 monitors, NDIR sensors are the gold standard. NDIR stands for nondispersive infrared. These sensors shine light through an air-filled tube inside the device, and a sensor on the other end of the tube measures how much IR light reaches the sensor. The difference in light emitted by the lamp and that which reaches the optical sensor on the other end of the tube indicates how much light is absorbed by CO2 and, therefore, how high the CO2 concentration is.
Although cheaper monitors may use different types of sensors, none of these is as accurate as an NDIR sensor – many aren’t accurate at all. Most other sensors are electrochemical and are known to be less accurate. Unfortunately, some manufacturers have begun to label their devices as NDIR when they are not. This has caused a lot of mistrust within the space.
Aranet4 uses a genuine NDIR sensor, which largely constitutes the product’s high price. In Wirecutter’s words, the NDIR sensor in the Aranet4 is the most accurate you will find outside of laboratory-grade equipment. It’s an exceptionally precise sensor, and there currently aren’t many other affordable devices with the same accuracy.
Of course, even within NDIR sensors, there are differences between accuracy and performance. Aranet4 Home uses a high-performance NDIR sensor from Senseair, a company with extensive experience with air quality sensors. Senseair notes that the Aranet4 Home uses its Sunrise sensor.
This sensor has a CO2 ppm accuracy of ±30 ppm or ±3% of reading. This is the same accuracy as mentioned on Aranet’s spec sheet. This puts it among the market’s most accurate carbon dioxide monitors and means it is more than capable of performing its job.
For the vast majority of cases, the slight variation of ±30 ppm or ±3% of the reading (whichever is higher) is irrelevant. These monitors help give us insight into the actions we need to take regarding our indoor air quality – actions that don’t differ if our concentration is 4000 or 4120ppm (+3%). Both readings indicate that ventilation is needed, and our actions should hardly differ from the 120ppm difference that may be witnessed on the Aranet4.
The Senseair Sunrise sensor is a single sensor – the humidity, temperature, and atmospheric pressure sensors included in Aranet4 are separate from the CO2 sensor. This is a different approach from sensors such as those offered by Sensirion, which includes all three sensors on the same chip.
Aranet lists a ±0.3 degrees celsius or ±0.5 degrees Fahrenheit margin of error for the temperature sensor. This means the sensor can accurately identify the air temperature in a given location and will allow users to act on temperature readings to maintain ideal indoor air quality conditions.
The relative humidity sensor used within the Aranet4 Home is similarly accurate, having only a ±3% fluctuation in accuracy. Finally, the atmospheric pressure sensor has an accuracy of – 2 hPa and + 3 hPa. All sensors in the device have minimal drift, and the device will be accurate even after years of use.
Overall, the Aranet4 Home (and PRO) are very accurate devices and among the most precise on the market. Especially compared to cheaper NDIR-equipped products, the Aranet is more accurate and will provide accurate readings for many years.
It’s also worth noting the carbon dioxide monitor can be recalibrated if needed. While I haven’t performed this process (I am worried about making the Aranet less accurate than it currently is!), it’s nice to have the option. It will come in useful for some users! The other three sensors in the Aranet4 Home cannot be recalibrated.
Real-World Use
From left: outdoor (ambient) CO2 reading. Underground train station CO2 reading.
Perhaps the best way to display the capabilities of the Aranet4 Home is to show the device in use. As I mentioned earlier, I’ve taken the device into various settings over the past few weeks and had some fascinating findings. Let’s dive into some of them!
The first two images, shown above, were taken in an outdoor park in Auckland – the biggest city in New Zealand – and an underground train station. I wanted to share the first image because it shows Aranet’s reading in a near-ambient setting. As of 2021, the atmospheric carbon dioxide level was just under 415ppm. Since then, it’s increased by slightly and now likely sits around 416ppm.
For three readings in a row, Aranet showed CO2 in the range of 420-426ppm. This is incredibly accurate and only very slightly higher than I would have expected. However, considering the park was located in the centre of a large city, the ambient reading might be slightly higher than the average.
The second image surprised me as I expected an underground train station to have higher CO2 reading. I was pleasantly surprised! With that being said, the train station was relatively empty (as you can see), and there was a lot of ventilation from the surface. I would expect a very different reading in a train station in Seoul!
From left: CO2 measurement in a domestic flight (during take-off). CO2 measurement in a taxi.
These next couple of images is where things begin to become interesting! Both of them show high concentrations of CO2, which also indicates poor ventilation. In the case of the first image (taken during a full flight), the reading also indicates a 4x transmission chance of COVID-19 compared to ambient CO2 levels.
Although aeroplanes have ventilation and filtration systems, these don’t activate until the plane is airborne. This means that during boarding, taxiing, take-off and landing, CO2 levels can become exceedingly high. This issue is only exacerbated since planes often have many people on board.
The latter image shows an even worse reading. This one was taken during an Uber ride but can also apply directly to a taxi or other car-sharing service. Since the windows were up for the journey, carbon dioxide levels quickly increased – even with only three of us in the car. This reading was taken about 10 minutes into the journey, and we eventually saw the CO2 concentration reach 4100ppm later in the ride!
The COVID-19 implications in this situation are also interesting to consider. Given that there were only three of us in the car, the chances of one person having COVID-19 and being able to spread it are quite low. However, had one person had COVID, the chances of the other two members catching it would be very high. Situations like this show the importance of wearing a mask while in taxis, Uber, and other ride-sharing services.
From left: CO2 reading in a public train. CO2 reading in a shopping mall.
The final two images I want to share in this section were taken on an (above ground) train and in a shopping mall. In both situations, I was pleasantly surprised by the ventilation. I’ve seen many Twitter users sharing images of their Aranet’s reading as high as 4000ppm on public transport, and I was amazed to see how ‘great’ the readings on this train were.
With that said, this reading would vary greatly based on how crowded the carriages are. Further, the trains in Auckland are above-ground, meaning they get fresh air circulated through them at every stop. Regardless, I was impressed because even at peak hour, I only saw the carbon dioxide concentration peak at 1100ppm!
I decided to take the Aranet4 Home into a shopping mall in the second image. The large shopping mall appeared to be very well ventilated as readings never exceeded 800ppm. Again, a great result showing that a well-ventilated shopping mall can manage carbon dioxide levels!
Overall, I had a lot of fun taking the Aranet4 Home into various settings. More than that, I’ve learnt a lot. Having a carbon dioxide monitor has allowed me to take a glimpse into a world I wouldn’t have otherwise known about. Or, at the very least, wouldn’t have been able to monitor.
App
I used the Aranet iOS app on an iPhone 12. Experiences may differ on other operating systems/smartphones.
From my experience using air quality monitors, one of the most lacking areas is typically the app. Although some air quality monitors have decent apps, they all lack in some way, making them frustrating to use. Of all the apps I’ve tried, the best apps were from uHoo and Atmotube. However, both apps were far from perfect – uHoo’s app was slow, and Atmotube’s didn’t do the best job visualising data.
I believe Aranet has created the first app in this field I would consider excellent. The app is fast, responsive, has never crashed on me, and provides data in a clear and easily readable form. Although some people may consider the app lacking or too simple, I think it’s perfect for the device.
The Aranet4 Home connects to your Android or iOS device via Bluetooth. While the Bluetooth range does not extend very far (I can’t use the app unless in the same room as the device), there is an option to extend the Bluetooth range in the app settings. However, I haven’t changed this setting as it decreases battery life.
By default, Aranet4 Home will update itself once every five minutes. This is adjustable, and the user can specify if they want readings every one, two, five or 10 minutes. Again, it’s worth noting that an increase in measurement frequency will decrease battery life.
Whenever you open the app on your phone, Aranet4 Home will send data to your smart device. This data will cover measurements the Aranet device has taken since you last opened the app. While I am not fond of this technique (since it can often be slow), it is a quick and painless process on this app.
Once you’ve given the app a few seconds to update, you will be able to see all carbon dioxide readings from the device since you last opened the app. On top of this, humidity, atmospheric pressure and temperature readings will also be updated, giving the user a complete graph of the four readings.
Analysing data on the app is exceptionally easy. Scrolling through the graphs is very fast, and I never noticed any hiccups. You can view data for the day, yesterday, seven days, or a custom date (as selected on the calendar). However, data will only be stored for two weeks, so keep this limitation in mind.
In the app settings, users can adjust measurement intervals, buzzer sounds, Bluetooth range, CO2 indication mode (what colours indicate what concentration), and CO2 calibration. Users can also toggle between temperature units, pressure units, and date formats to keep the device easily usable for everyone.
Overall, the app is fantastic. It’s not overly complex but still provides essential data in an easy-to-use format. I haven’t encountered a single crash or hiccup with the app, and it’s worked flawlessly thus far. It even allows users to export data (via the share menu) to be analysed on other programs and devices.
Price & Lifespan
The Aranet4 Home is considered one of the best consumer-level carbon dioxide monitors on the market. Due to this, the device has a premium price compared to many competing products. At the time of writing, the Aranet4 Home costs 249 USD.
This is far from cheap, and the pricing might seem very steep for a device that monitors only CO2. Unfortunately, this is one of the biggest issues with CO2 monitors at the moment – they have a steep barrier to entry regarding the price.
With NDIR only recently entering the consumer market, prices for this technology are expensive and likely will be for a while to come. While there are cheaper alternatives out there, many are not accurate – for accuracy, you’ll want to ensure the device has an NDIR sensor. These sensors don’t come cheap, though.
With that being said, these devices are highly accurate, and if you can afford to get an NDIR-equipped device such as the Aranet4 Home, you can rest assured that you will be getting accurate CO2 readings for many years to come.
Therefore, while $249 may seem like a steep price (and it is), it isn’t an unrealistic price. Compared to the other air pollution monitors I’ve used, Aranet4 has the best smartphone integration via its app. It’s also incredibly easy to use, well-built, and highly accurate. Overall, this CO2 monitor simply provides a very complete package.
| Device | Price | Accuracy |
|---|---|---|
| Aranet4 Home | $249 | ± 30 ppm OR ± 3% |
| Qingping Air Quality Monitor | $129 | ± 30 ppm OR ± 3%* |
| Qingping Air Monitor Lite | $100 | ± 70 ppm OR ± 3% |
| Temtop M2000 | $225 | ± 50 ppm OR ± 3% |
| Wohler CDL 210 | $219 | ± 50 ppm OR ± 3% |
As for the lifespan of the Aranet4 Home, provided the device is treated well and doesn’t get damaged, it should be able to provide accurate readings for many years. In addition, the CO2 sensor can be recalibrated and therefore suffers from no sensor drift.
Some drift can be found over time in the temperature, humidity, and atmospheric pressure sensors. However, the drift is generally minimal and shouldn’t impact your device usage – even after five or more years.
Battery life is similarly incredible. While it varies based on the frequency of readings, the minimum battery life is around eight months. This is with updates every 1-minute, an option that most people won’t enable. However, if you lower the readout times to once every 4-minutes and use lithium batteries, the device can have a four-year lifespan!
If you pair the Aranet4 Home with some rechargeable double-A batteries, you have a device which can be recharged once per year and has no waste. This is how I’ve personally used the Aranet4, and I recommend it to anyone who doesn’t want to spend money on disposable batteries.
My biggest concern with the longevity of the Aranet4 Home is user damage. The device is not waterproof or water-resistant, so you must ensure you have a dry spot in your bag if you plan to take it out and about. Further, it’s not drop resistant, and any major drops could instantly break the device.
However, if you take care of the device, it can last many years, making the Aranet4 Home a good investment if you are concerned about air quality. This lifespan, combined with the overall package of Aranet4, makes it a device I recommend – even at its steep price.
Is Aranet4 Home Worth it?
If you were to ask me whether or not I recommend the Aranet4 Home, my answer would be yes. This is a very precise carbon dioxide monitor that easily fits in your pocket, bag, or even alongside your computer on a desk. It’s straightforward to use but still provides the essential settings and allows for manual calibration.
The only aspect that makes me hesitate when recommending the Aranet4 Home is the price. It’s far from cheap, and there are more affordable monitors on the market. If the cost of the Aranet4 Home is too high for you to justify, it would be better to pick up one of the competing monitors instead.
However, some people will be okay paying the premium. The built quality of the device is great, even if the whole product is plastic. The accuracy is best in class, the battery life is fantastic, and the app worked flawlessly throughout my time with the device.
This combination of factors allows me to recommend the Aranet4 Home despite the price tag. It offers a complete experience, and worked flawlessly throughout my time using it. While there are a few minor changes I would like to see, these are simply to fine-tune an already great experience.
My biggest wish for the device is to see more protection added. Currently, it’s not water resistant, and it doesn’t have any drop resistance. While I understand air must enter the device, I’m sure there is some way to make the device at least somewhat water resistant. In addition, some extra drop protection would also be wonderful.
Do you have any thoughts or experiences with Aranet4? If so, please feel free to share in the comments down below! Alternatively, if you have any questions about the device, please feel free to ask, and I will do my best to answer. Thanks for reading!
Aranet4 Home FAQ
What Is the Difference Between the Aranet4 Home and Aranet4 PRO?
Both devices are physically the same and offer the same capabilities. However, the differences come in the form of connectivity. The Aranet4 Home is designed as a standalone device, whereas the Aranet4 PRO is designed to be used with multiple devices alongside an Aranet4 PRO Base Station.
How Accurate Is the Aranet4 Home?
The Aranet4 home is accurate within 30ppm.
Where Can I Buy the Aranet4 Home?
You can purchase the Aranet4 Home from Aranet’s Amazon store. You can also purchase it from Aranet’s E-store.
What Does the Aranet4 Home Monitor?
The Aranet4 Home monitors carbon dioxide concentration, temperature, humidity, and atmospheric pressure.
What Alternatives Are There to the Aranet4 Home?
The most popular alternatives are Qingping air quality monitors. However, these tend to be less accurate.
Aranet4
The Aranet4 Home and Aranet4 PRO are two of the most popular carbon dioxide monitors currently available. With high accuracy and a straight-forward and easy-to-use design, these monitors have set the standard for portable carbon dioxide monitors.
Product Brand: Aranet
4.5
Pros
- Highly accurate
- Easy-to-use
- Pocketable & easily portable
- Great app experience
- Long battery life
- Customisable readout times
- Good build quality
Cons
- Expensive
- Somewhat fragile
- Some sensor drift
Hello, please note that in trality you CAN export data from the Aranet4 App, on an Excel file (csv format): just click on the button at top-right corner of the graphs-window and you will get your .csv file that you may share on WhatsApp, email, and so on.
The button is also visible on the App screenshots that you have posted above to show the graphs of CO2 from App.
Perhaps you may review the document accordingly? In such case, you may even cancel this comment…
By the way: congratulations for the review: very well done and your way of writing is so good to explain complex things: BRAVO!
Hi,
Firstly, thank you so much for the kind words! I appreciate it.
You are totally right regarding the exporting of data – I missed that as I didn’t expect it to be under the ‘share’ button! I’ve updated the article now. I am very happy to see this capability within the app!
I’ve used one for about 6 months now. Made me happy about my office and sad about my house. In terms of protection, I just leave it in the original packaging in my backpack and use the app to interrogate it – the amount of buffering does not appear to be significant, although does make it a little awkward in restaurants…
Hi Duncan,
Thanks for sharing your experience! By original packaging, do you mean the box?
Yes.
This was a thorough and excellent review. Thank you for spending the time on it!
You’re welcome! Thank you for the kind words 🙂
Also take a look at co2.click, a Canadian designed and made CO2 sensor solution. Connected (Model C), cloud portal with 48 months of data retention, dual-beam NDIR technology. Model D is local storage only. And lower cost than the Aranet4, the co2.click starts at 189$CAD (~138$USD).
Review by @jeffgilchrist here: https://twitter.com/jeffgilchrist/status/1528016215779713024
Thank you, I will!
Regarding the person that left the unit in the box to protect it, would it get adequate readings if it was packed up like that?
Also, how quickly does one get an accurate reading from the device?
Hi Nathan,
I’m not sure what the box looks like, but if it doesn’t cover the vents on the device, it should still function as normal.
Readings should be accurate out of the box as it is factory calibrated! If not, you can manually calibrate it and begin getting accurate readings within a few hours.
I wish it worked with Smart things / Z-wave / make.
I think that the accuracy data in your table is slightly incorrectly stated. I think the accuracy should be stated as +/- (30ppm + 3%), not “OR”.
Great review.
Hi Larry,
Looking back at the spec sheet, you may be right. I interpreted it as whichever was larger. I will check with Aranet and confirm!
Thank you for pointing this out.