SAF Aranet4 Home: Wireless Indoor Air Quality Monitor for Office or School (CO2, Temperature, Humidity and More) Portable, Battery Powered, E-Ink Screen, App for Configuration & Data History

I've owned several CO2 sensors. In particular, I've had 2 Awair Glow units, 1 first-generation Awair unit, 1 second-generation Awair unit, and a TIM10 CO2 sensor. Of these sensors, the TIM10 is my "gold standard" sensor, but it has the very, very annoying property of requiring AC power. Aranet4 promised to be a battery-powered CO2 sensor that could output data to an app. It delivers, but it requires calibration out-of-the-box, in my opinion. Measured against known good sensors (particularly my TIM10), my Aranet4 sensor read about 75ppm higher than the environmental level out-of-the-box. The app warns you that performing calibration will permanently erase the factory calibration data, which is somewhat scary, but I did it anyway. In order to validate that the calibration was successful, I had my trusted TIM10 sensor outdoors, connected to AC power, out of the sun, with the Aranet4 directly next to it, on a substantially windy day with extremely good air quality (as measured by PM2.5 and PM10 presence from AirNow and Purple Air). The floor, outdoors, in this configuration, as read by the TIM10 unit, was 380ppm of CO2. Before calibration, in the same environment, Aranet4 reported 480ppm. After calibration, Aranet4 reported within 15ppm of TIM10, which I considered a success, particularly given the rarity of having such a low reading. All of the Awair units bottom out at 400ppm. Following calibration, for the last few weeks, I've kept an eye on Aranet4 and TIM10 when they've been in the same room. There's approximately a 10-15ppm disagreement between TIM10 and Aranet4, which I consider a very acceptable deviation given that Aranet4 is battery powered, and TIM10 is AC powered. On the app side, Aranet4 provides a serviceable iOS app. The iOS app itself is perfunctory. It provides graphing, exporting data (as csv, including CO2, pressure, humidity, temperature, and date of sample), and basic reporting features. It doesn't support dark mode, though, as an example of its perfunctory nature. The app developers didn't consider the performance impacts that storing all of the data would have on the graphing component, though, so the app gets laggier the more data the sensor measures. You're also only going to get a week of data for historical measurement. Other details are worth mentioning beyond the sensor accuracy and app integration, though. E-ink, as a display type, is just awesome. It looks very nice, aesthetically. Each refresh blanks the screen temporarily, though. Keep this in mind, if you decrease the measurement interval (you can measure as frequently as once per minute). Also, there's no backlight, which is why the battery life is good, but keep this in mind too, if you want to see it in the dark. I've taken this sensor on an airplane, and it works great there too. It's just an incredible sensor to have -- you can pocket it or bring it somewhere in a backpack and still have CO2 measurements, where most sensors can't go. For travel, or just in general, it's a great device to have. After calibration, it measures very accurately, and I'm happy with my purchase all around. However, I'd say calibration is mandatory. I've included a screenshot of a graph made from the CSV, as well as the CSV data from the unit itself.

We have been using this carbon dioxide (CO₂) monitor for the past 18 months to check carbon dioxide levels in our home and work areas. CO₂ levels are a key measurement to assess the quality of indoor air and ventilation, which are important for minimizing the risk of virus transmission. One of the main reasons we bought it was to monitor how good the ventilation is in our indoor rooms. For example, in our home office, when the readings went up to 1,000+ ppm (parts per million), we noticed that our thinking slowed and we felt more sluggish. Decisions become more difficult to make. Apparently, our experiences match scientific studies that have proven that high levels of carbon dioxide can impair cognitive function and make it harder to think and be productive when CO₂ levels hit 1000 ppm and above. Thanks to this air quality monitor, we also noticed that if a second person enters a room, the CO₂ levels can increase quite rapidly just from our breathing. The CO₂ readings can sometimes double. We open a window to bring it back down to a good range. This monitor is small enough so that you can hold it in your palm and move it around easily. It looks both sleek and functional. Big bonus: it also provides temperature and humidity readings, and you can select either Fahrenheit or Celsius. To have all these readings all on one small device is very handy. It runs on two AA alkaline batteries, which are included. There is a helpful bar showing how much battery life is left. We have had our unit for 18 months, and after continuous use, we have not had to replace the batteries. The e-ink display digits are bright, easy to read, and large (roughly half an inch tall). The large digits and color bar allow you to quickly glance at the device from a distance and assess whether to take action to reduce CO₂ levels. There is an air quality bar that has three colors: green, yellow, and red. Each color corresponds to a different CO₂ level: green for normal (good), yellow for elevated (average), and red for high CO₂ levels (unhealthy). The second reason we purchased this monitor is to get an idea of how high the risk of respiratory virus exposure is. Higher CO₂ levels indicate poor ventilation, which can lead to higher airborne virus concentration. Scientists have found that people in a room with higher CO₂ levels are at a higher risk of virus infection than people in an identical room with lower CO₂ levels. Therefore, knowing when the CO₂ levels are high allows you to know when to reduce risk by opening windows to allow fresh air in, wearing a high-quality respirator mask, and/or reducing the time spent in that space. One feature we like is that you can use it with or without the app. So there is no pressure to use the app. Our only wish is that it came with a protective cover. In sum, this is a high-quality, reliable, and easy-to-use CO₂ monitor that allows you to continually assess air quality and ventilation. This was quite an investment, but well worth it. Highly recommended.

The aranet4 is such an excellent monitor, and really is the best bang for your buck in an accurate and easy to use monitor. We have used this in all the rooms of our home to measure air flow and how quickly C02 builds up - especially useful in the kitchen during various cooking processes and in the bedrooms overnight - but we have also brought it to work to measure the C02 and get an idea of the air flow in various offices as well. It's easy to set up, the battery life is excellent, and it's easy to bring with you anywhere. The app works well and is likewise a quick and easy setup. We keep this monitor in the main living area of our house and it's every easy to monitor when the C02 is accumulating and we need to crack a window or turn on an exhaust fan. It's been illuminating. This item is also very accurate, and more so than others and cheaper version. Totally worth the money and a reliable, trustworthy device for monitoring a really important aspect of our health.

Not the cheapest for sure, but like many things, you tend to get what you pay for. In this case, for me, after over almost 3 years of continuous use a device that's: - reliable, accurate (tested against calibrated devices) and convenient - tested in NE USA and SE Asia, and even used carried in a bag through subway systems - battery lasted about 2 years - excellent reporting/charting app (7 days worth of readings - exportable as .csv/.xlsx) and bluetooth comms, flawless device firmware updating Easily worth the money over time.

This CO2 monitor -- the product of Latvian engineering -- is one of the most awesome gadgets I have ever purchased. It's extremely accurate, unlike other cheap CO2 monitors on Amazon. It syncs with your phone using Bluetooth, so you can see CO2 levels over time (this is a killer feature that other monitors don't have). The e-paper display is incredibly clear. The batteries last for many months. It's very compact -- easily fits in a pocket. It's super interesting to analyze CO2 levels as you move into different spaces, e.g. when you board a plane, when the plain is airborne, etc., since CO2 concentration is a proxy for COVID risk. I was on an old Embraer jet, probably 30 years old, and the CO2 levels hit the highest level I have ever seen, 3550ppm! (The outdoor level is about 450ppm.) Also, not many people know this but you can measure cognitive decline starting at about 900ppm of CO2 -- and many apartments, especially new constructions, get way over this level. See the paper "Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments", Allen et al., Environmental Health Perspectives, for some shocking numbers about this. Once you start frequently monitoring CO2 levels, closing the biofeedback loop, two things happen: (1) you develop a new 6th sense -- you can start to predict the exact CO2 level just by how the air feels when you breathe it in. I can often guess the CO2 level to within 50ppm, without looking at the Aranet4. Weird and pretty cool. (2) You start to get really conscious just how stuffy the air is, and how much your cognitive function slows, even when the CO2 levels are high.

The Aranet4 has a lot going for it. The battery life is excellent: it allegedly runs for years without needing a power source. It’s also said to be very accurate, and I’ve seen nothing to suggest otherwise. The app is well designed, with useful historical charts, and it’s nice that all data stays local without any cloud dependencies and related privacy concerns. That said, two inexpensive meters I own (Unni and Newentor, around $30–35 each) come surprisingly close in accuracy: typically within 0 to 40 ppm of the Aranet4. Given that, the >$140 price tag may be hard to justify for many people. It also updates less frequently than cheaper models with USB power supply, even at its fastest setting (once per minute, which will likely decimate the runtime ... default is every five minutes). However, I had to parse hundreds of reviews (thank you, LLMs) to find those two cheap and reliable devices. A $17 device I tried was total crap. One small note: the Aranet4 consistently reads humidity higher than my two budget meters, which usually match each other. Not sure which is more accurate, but it’s worth mentioning. Overall, a well-built and reliable device, just expensive for what most users may realistically need. If used at home, a cheaper USB powered device with always on screen backlight and much higher display update frequency might be the better choice.

I got the SAF Aranet4 Home mainly because I was curious about why I'd get so groggy in one particular room of my house. This little gadget was easy to set up right out of the box and it immediately started giving me the lowdown on my air quality. Turns out, the CO2 levels in that room were off the charts sometimes - no wonder I felt like I was in a brain fog half the time. I love that the Aranet4 is portable. I've taken it with me on trips, and it's kind of become my travel buddy. It’s wild to see the CO2 levels on airplanes and in hotel rooms. The color coding on the device makes it super easy to understand when the air quality is getting bad, and the buzzer is a neat feature too, although I turned it off after a while because it startled my cat. The app is simple and does the job. It keeps a record of the air quality data, so I’ve started geeking out on comparing the air quality in different places I go. The e-ink display is clear, and the battery just keeps going - haven’t had to charge it yet! The Aranet4 is not just a fancy gadget; it’s been a real eye-opener for me. It made me realize how the air quality around us can affect how we feel. Now, instead of guessing, I know when to crack open a window to get some fresh air in. It’s pretty satisfying to see the CO2 levels drop and feel that mental clarity kick in. Honestly, in these COVID times, it’s comforting to have a better grasp on the air I’m breathing, especially in new or unfamiliar places. So yeah, I’m really glad I got the Aranet4. It’s helped me understand my spaces better and take simple steps to improve the air quality around me. Plus, it’s kind of fun having this little gadget with me, measuring the unseen world of air quality wherever I go. Update: have lent the device to several friends now to test their apartments, and they've all found ways to improve their air quality!

I love this device and bring it everywhere with me. The display is intuitive and easy to read, easily connect by bluetooth to my phone and other devices, the responsiveness can be updated to short intervals for constant monitoring room-by-room or set to longer time durations if the unit will be stationary in one room for a while. Easily switch between metrics. A+ for indoor air quality awareness!