Edit (May 16, 2023): The app in iOS has now been updated, which according to Customer Support was the culprit behind the Wi-Fi disconnections. After the update, things seem to be working normally now. As such, I've raised my rating to 4 stars. Minus 1 star for lack of real-time updates (app updates let's say every 7-10 minutes, you can't simply refresh on a whim and expect new numbers to appear), and of course, that you cannot roll out an app that critically kills a key feature of your device! But a happy ending nonetheless.

Edit (May 3, 2023): I also take back my comments on customer support. Seemed friendly enough but it seems since I've exhausted options, they have simply gone to ignoring me. As I'm traveling with the device, I will miss my return window, so I have a $300 paperweight. Proceed with caution, don't throw away the box, and at the first sign of trouble, make sure to return it.

******** (Original review below).

This simply will not maintain a Wi-Fi connection so doesn't sync its data, which makes this device (to me at least) only usable at a standalone device, defeating half of the purpose of the device. Have gone through troubleshooting with the AirThings guys, they seem helpful and friendly, but nothing has worked.

I have to give this product a miss. I may be one of the unlucky few.

Tl:dr
I recommend this product. I believe that it is currently the best on the market and provides a good array of sensors for the price. I have not received any financial or other consideration for this review. I have no connection to the company. Details, positive and negative, are found in the review.

Intro: In operation (after 7-day calibration) for three weeks beginning October 2021. Unit is located indoors in the bedroom of a small single-story home in northern California. I purchased View Plus after an online evaluation of competitive units. The purchase decision was based on the array of sensors, acceptable display of sensor parameters, appearance of a good user interface, ability to easily download the data in Excel .csv file format, designed in Norway, and assembled in Tunisia (visible in product photos). I expect that this is the first product that I've ever owned that was assembled in Tunisia. There were no Amazon reviews as I purchased the unit as soon as it became available.

My primary motivation for purchase was to measure indoor particulate pollution during the wildfires. I wanted a more quantitative measure than the colored indicators on our air purifiers. However, I have since become more interested in the carbon dioxide (CO2) and VOC levels. The inclusion of Radon, temperature, humidity, and atmospheric pressure sensors is a plus.

Particulates: I have had an extended conversation with Airthings via the app. They are responsive, although it may take a few days or even a week, if you ask technical questions as these need to go to the engineering team. As this is a consumer and not scientific device, there are cost limits on the nature of the particle sensor. Airthings does calibrate the particulate sensor to a scientific instrument. However, the Airthings sensor is most likely not able to distinguish between different particle size and scattering distributions that give the same overall signal. I had plans to do a cross correlation study with a scientific instrument, but circumstances conspired against me.

At this time, I am satisfied that Airthings has done enough work that the threshold limits (green 25 µg/m3) for the PM 2.5 sensor are reasonably close to the equivalent limits used by the US EPA and European PM 2.5 AQI. For the data that I've collected, there is very little difference between PM 2.5 and PM 1 signals. I have not investigated why. One caveat is that the data collected so far has an average PM 2.5 and PM 1 values of only 2 µg/m3 and only a single peak greater than 25. Since the rains have (finally) come, I don't expect to have the opportunity to check against more polluted air conditions in the near term.

Carbon dioxide: This provided the most surprise about the conditions in our home. I found that ventilation in our bedroom is insufficient to keep levels in the green without the window(s) being open at night. I am looking into ways to ameliorate this problem when keeping the windows open is not an option. When I first received the unit, I placed it outdoors to see if it would read the expected value of about 400+ ppm for average CO2. The unit read about 550, but it was before the 7-day calibration was completed. Over the course of the past month, when the room was well ventilated, I observed readings as low as 469 ppm. The unit will show the increase in CO2 when either 1 or 2 people are in the unventilated room for any significant period of time.

VOC (volatile organic compounds): The measurement is in parts per billion, ppb. This is my first experience with VOC data recording. The unit is certainly responsive and exhibits significant signal when we are cooking, especially frying. As there are many different types of VOC, I cannot comment on whether one should take significant actions based on the results in the home. Do fry-cooks have career related health issues? At a work environment, such as an organic chemistry lab, there may be many types of VOCs that are clearly harmful to health.

Radon: All the values that I have recorded are below the green threshold limit of 2.7 pCi/L (picocuries per liter). The average value over 2000 measurements is 0.7 and has a standard deviation of ±0.4.

Temperature: Comparing the value to household sensors indicates that the temperature displayed by the Airthings sensor maybe between 1- or 2-degrees F high. However, I consider that within measurement error for accuracy given the nature of the other sensors. Precision appears to be excellent.

Relative Humidity: Comparison only with household sensors. Appears to be within a few percent.

Atmospheric Pressure: Excellent agreement (within 0.5 mBar) with external values (local weather data). Range of data recorded between 1001 mBar and 1022.5 mBar.

User Interface (Unit): There is an E-Ink type display that is not illuminated. This is a very low power display and conserves battery. No power used to maintain the current display reading. It has high contrast and easy readability. You can choose 2 sensors to display via the app (Phone or PC). When you wave your hand in front of the unit, it indicates its assessment of the overall air quality (good, fair, or poor) and shows any of the readings that cause a fair or poor result. It then returns to the standard readout. I have not found the lack of illumination to be detrimental.

User Interface (Phone): I'm using a Samsung Galaxy A51 with Android 11. The software allows you to choose among several devices that you might have. As I have only one, it displays a summary that is in the attached photo. You can then tap "VIEW IN WEB DASHBOARD" to get graphic displays for different periods of time. You can choose to get notifications via the app, if values exceed the Airthings recommended thresholds. You can choose the sensors for which to have notifications sent. These thresholds cannot be changed. I think it would be good to be able to change the thresholds with the understanding that one is responsible for the values used.

User Interface (PC/Web): I'm using an Intel-based PC running Windows 10 Pro and MS Edge for this unit. See attached photo. The graphing is generally quite good. I'd prefer to be able to choose the order in which the different sensors are displayed. It might be possible to do this by deleting sensor graphs (called tiles) and then adding them back. I've not tried that. The vertical scaling is automated and determined by the range of values of the data being displayed. The scale cannot be changed, but you can zoom using touch, if your computer/phone has that capability. Adding the historical data (not shown in the photo) will expand the vertical size of each graph and give the minimum and maximum value for the data range.
Bug: You can add a tile for the outdoor weather, but only for Oslo, Norway! They have given me instructions for changing the location, but the software for the View Plus is not the same as for the software shown in the instructions. I have made them aware of this. It is unclear to me whether they can and will offer software updates.

Downloading Data: The .csv file contains the time and sensor data for the entire time the system has been recording for that location. If I don't do something to re-start history, the data file will eventually grow to unmanageable size. They should allow you to specify the range or use the range chosen for the graphing display. The file name is also fixed as the serial number of the unit. These are serious limitations given the extra work caused for the user, I consider them bugs.

The data are separated by semi-colons, so converting from text to columns in MS Excel is easy.

The data are recorded with a UTC time stamp. Since I'm in California, it is easy enough to subtract 7 hours and put the local time in the next column.

The headers have a few character-conversion bugs: "μ" instead of "µ." The character "Â" is inserted in the Temperature column header. These are minor.

The date/time format is 2021-09-30T20:04:28. The "T" separator is a nuisance and prevents Excel from recognizing the form of the data. If they would replace the "T" with a space, then Excel would have no trouble. I use the replace function to do this. Again, it is no big deal, but should be a simple fix. I have made Airthings aware of these bugs.

I will append this review, if I find additional information that may be pertinent to other users. I hope this has been helpful.

Appendix 1: I've added a comparison of the PM2.5 data from the Airthings View Plus (indoors near an open window) to Purple Air data from an outdoor sensor (not mine) about 100 meters from my home. The Purple Air data are shown in the US and European scales. The data are for the 24 hours of October 29, 2021. Correlation is excellent for the main peak.

The View Plus (2960) measures radon, PM, CO2, VOC as well as humidity, temperature and pressure.
It also can display outdoor weather and temperature in areas where that service is available. We have it in our bedroom to keep track of indoor air quality where we spend 1/3 of every day. It's also great to see the outdoor temperature next to the bed when we wake up in the morning.

I originally purchased the View Plus (2960) and one Wave Radon (2950) detector because we live in a high radon area (central Ohio). The 2960 has Wi-Fi and will collect data from other AirThings products and upload it to the AirThings dashboard. The wireless communication between the 2960 hub and the 2950 sensors is a proprietary protocol using the IEEE 802.15.4g standard. This is similar to Zigbee, INSTEON and Nest Protect home automation products.

Based on my experience with other home-tech devices, I downloaded the app, and had all the devices near each other when I configured them. So, I had no difficulty setting them up. But wireless interference could be a problem and all of mine are within 50 feet of the hub.

We put the 2950 in the basement. The dashboard is very helpful with radon because radon varies from hour to hour, day to day and seasonally. It is the long term average that indicates whether a health risk exists. I have a home office in the basement, and I've included a snippet from the dashboard of the radon levels recorded from late January through November 2022. This shows the variation, and how bad the levels were (over 22 pCi/L). Once we installed a mitigation system, the levels have dropped below 2 pCi/L.

After the initial two weeks and I saw how bad the radon was, I purchased a second Wave Radon (2950) detector to have units in two parts of the basement (crawlspace and home office). After three months of monitoring, I was convinced we had a problem and we scheduled a radon mitigation contractor which was completed a few months later.

After 8 months, I had a problem with the 2960. It showed really large numbers, then 0. I had already installed a mitigation system, so this was confusing. I purchased an AirThings Corentium to put side by side with the 2960, and proved to myself that the unit indeed was defective. The support person who originally picked up the ticket did nothing, and email for warranty service was ineffective. So I mentioned this in my previous review (since replaced with this one), and within two days a good support agent picked up the ticket, and helped me with the RMA process. It was disappointing that the unit failed, and that initial support was not helpful. However, the second agent was proactive, professional and communicated well and I was able to return the 2960 for a replacement unit. I've had the replacement for a week now, and it seems to be working fine. Based on the excellent response from the second agent, I will continue to recommend these products to friends. I can't quite give the product 5 stars because of the failure of the first agent, and the initially nonresponsive warranty process. However, if the product continues to do well, I can see myself raising the rating back to 5 stars at some future date.

As a final note, if you are not sure if you need radon mitigation, and are wondering whether you should spend the money or are just technologically afraid, the AirThings Corentium is a great product too. It has no smart phone or Wi-Fi integration, but is a simple-to-use product that utilizes the same sensor that is in the 2950 and 2960 and gives 1 day, 7 day and 30 day average readings.

Living in the Northeast part of Pennsylvania, Radon is a big concern in our state. More than 40% of all homes in the state have Radon levels above 4.0 pCi/L, which is above the Environmental Protection Agency's action guideline. When I purchased my home in 2016, one of things added during the sale negotiations was a Radon mitigation unit. I did the carbon follow-up tests after we moved in but never thought about actively monitoring it and assumed having a fan meant I was good. I haven't used those tests for some time, so I figured having something that's actually able to read it for me and provide me hourly info would be worth my investment. So, I got one of the AirThings View Plus units and placed it in my basement to track. For months I watched my numbers go up to 12-15 pCi/L and some days as high as 20! The lowest it seemed to go was maybe at most 5-7 pCi/L and I finally called the radon mitigation company that installed unit prior to our move.

I found out most fans only last about 5-7 years and our fan was going on the unit, so I had to get a whole new fan that was also bigger than the one that was originally put on. It only took them about an hour of work to swap it out and get the unit back and running and after that I watched the levels drop and drop and drop down to barely anything recorded on my AirThings. If it wasn't for this AirThings unit, I probably would have never known my radon levels, never got the fan replaced until it actually locked up or stopped working all together all while dealing with harmful Radon levels.

Another bonus for tracking in my basement is the humidity levels. I use a dehumidifier mostly in the summer months, so it's good to track it during the rest of the year to make sure it's not spiking, and when I need to have it turned on for those spikes if it's starting to get up to the 70% range. Before this, I just used a simple analog humidity hygrometer that I would have to go down into my basement to check the levels and make adjustments as needed. I also invested in a second unit for our Bedroom to track air quality as well as Radon, so I might look into another unit in the near future for our first floor.

Outstanding range of sensors. The app is the heart of the system. You cannot review every reading on the unit itself - you MUST use the app - but that's fine with me - it provides SO MUCH more information that cannot be displayed effectively.
Easy install, easy setup, provides solid information and the longer it runs, the more data you collect and begin to see the impact of daily living in your home - i.e. burning scented candles all day. :)
Highly recommended.