Product Reviews

Plume Labs Flow 2 Review: The Best Air Quality Monitor Just Got Better

James Frew 15-11-2019
Our verdict of the Plume Labs Flow 2:
The Flow 2 is a worthy successor to Plume Lab's original air quality tracker. With upgraded sensors, data export options, and an attractive new finish, the Flow 2 is a must-buy.

Air pollution is a problem for us all. However, one of the challenges is that, in most cases, you can’t actually see the pollution around you. This means you can only use generic protection advice, or publicly available local data, where it exists.


The Plume Labs Flow 2 is a portable, palm-sized device that helps you visualize your current exposure. By syncing via Bluetooth to your smartphone, you can use the $160 device to track and analyze the data over time. It’s available to pre-order now with delivery expected by the end of November.

So, should you buy the Flow 2? Let’s take a closer look.

Flow 2 Design

Flow 2 hanging

As the name suggests, the Flow 2 is the successor to the original Flow Plume Labs Flow: A Portable Air Quality Monitor That'll Keep You Informed With pollution all around us, the Flow may be one of the most essential and vital devices you can buy. Read More device, which was released in 2018. The form factor remains largely unchanged this time around, although there are two immediately noticeable differences. First, the device is now a dark graphite grey rather than silver. You can attach the Flow 2 to your bag or belt using the strap. The original Flow device used a brown pleather strap, which has now been replaced with a silicone black strap.

Flow 2 underside


These two changes make the device less conspicuous, and it now fits in aesthetically with most of your other tech products. Switching the strap to silicon rather than pleather should improve durability too. The Flow 2 is almost rectangular, sloping in slightly towards the top where the strap connects. The base of the device is coated in a durable plastic, which shelters the USB-C port and charging pins on the underside.

Flow 2 upper air holes

If you haven’t seen it before, the front of the device is rather unusual. The top half is covered in small holes that allow air to flow through to the sensors underneath. The lower half is dedicated to a capacitive button. When pressed, the current pollution level is displayed using colored LEDs that surround the button. The LEDs operate on a traffic light system, ranging from green for low pollution, to red for severe levels.

Flow 2 Battery Life

Flow 2 charging ports


One of the first questions people usually ask about wearable technology like this is whether you’ll have to charge it each night. The short answer is, most likely, yes. The battery lasts about a day, but may vary depending on how often you activate the display and if you choose to enable the always-on Bluetooth connection for GPS tracking. That said, I found myself charging the Flow 2 each night regardless of whether it had run out of battery.

Flow 2 on wall

This is because the Flow 2, like the Flow before it, comes with a convenient charging dock. All you have to do is place the Flow 2 into the dock, and it begins charging through the charging pins underneath. For those who already purchased a Flow device, the Flow 2 is compatible with the original dock as well. If you run out of juice on-the-go, you can give the Flow 2 a top-up using the USB-C port.

It’s possible to extend the monitor’s battery life through the use of Idle mode, which can be enabled in the Flow app. This effectively puts the sensors to sleep for a while. You can choose between 20 minutes, two hours, eight hours, or 24 hours. This isn’t a fixed setting; just tap the Flow 2’s button, and the device will exit Idle mode. Using this new mode could see the Flow 2 last up to three days between charges.


The Flow Mobile App

The Flow mobile app, available for Android and iOS devices, is where you can dig down into the data the Flow 2 records. While the device itself only shows a traffic light system of warnings for quick reference, it is actually collecting a wide range of air quality data. The device connects to your phone via Bluetooth. There are two connection options; in-app and always-on.

The always-on connection is used to record GPS location data alongside your Flow 2’s measurements. This is done using your phone’s sensors as the Flow 2 itself doesn’t have a built-in GPS sensor. This connection does have an impact on battery life but allows you to capture more useful data. The Flow 2’s measurements alone are interesting, but their potential is unlocked when viewed alongside location.

The app’s main page is a chronological feed of your Flow 2’s recordings, broken down by day. The daily overview contains a color-coded line graph of your exposure by time, with a high, medium, or low rating underneath. Because the device tracks a handful of air quality measures, Plume Labs developed its own Air Quality Index (AQI) to summarize the data. The daily AQI is also listed in the feed.


Tapping into a specific day displays any recorded GPS data, in addition to a more detailed graph, which can be split between the different tracked particles. This line graph is overlayed against the combined average exposure, allowing you to see each particle’s contribution. Sliding your finger from left to right along the chart shows a minute-by-minute snapshot of recorded data.

Flow 2 Data Analysis

Flow 2 amber LEDs

The original Flow device recorded some of the most critical air quality readings, like PM2.5, PM10, NO2, and VOC. The Flow 2 maintains those sensors but adds a new one for PM1. This is an incredible achievement. PM1 particles are ultra-fine and are often directly implicated in many of the health issues caused by air pollution.

These minuscule particles can pass through the majority of air filters and enter our lungs. That the Flow 2 can detect them at all is a testament to the work Plume Labs has undertaken in little over a year since the original Flow device.

Flow 2 green LEDs

One of the problems we identified during our review of the Plume Labs Flow Plume Labs Flow: A Portable Air Quality Monitor That'll Keep You Informed With pollution all around us, the Flow may be one of the most essential and vital devices you can buy. Read More in 2018 was that, despite an attractive interface, it was hard to analyze your data within the Flow app. With the release of the Flow 2, Plume Labs have enabled an export option in the app, which collates your data and emails you a download link. The data is broken into three parts; GPS images, GPS location data, and air quality recordings.

The GPS images are the same as those shown on the in-app daily summaries. Helpfully, the GPS data then comes in the form of a KML file. Probably the most important, though, are the air quality recordings. These are presented as CSV files, which should allow you plenty of opportunities to filter and play with the data. Although this seems like a small feature, it dramatically improves the usefulness of carrying the Flow 2 around with you each day.

Should You Buy the Flow 2?

The Flow 2 represents a significant step forward in tracking air quality thanks to the new PM1 sensor. It builds upon the foundations laid by the original Flow device. The Flow 2 is portable, easy to use, and tracks some of the most critical data. Crucially, that data is now yours to examine thanks to the new export feature.

If you don’t want to deep dive into the recordings, though, the Plume Labs have perfected the way they communicate air quality data. The colored LEDs make it easy to understand your current exposure, and don’t require you to unlock your phone to do so.

Coupled with these features, the portability of the Flow 2 makes it an indispensable companion, keeping you informed and able to make useful changes to reduce your exposure.

Enter the Competition!

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Related topics: Health, MakeUseOf Giveaway, Smart Sensor.

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  1. Andrea
    June 18, 2020 at 8:22 am

    Thanks for the review of the Flow 2.

    But I would not be so positive about the Flow without cross checking with other portable devices like the AtmoTube PRO, which I find more reliable. I explain why.

    I have bought three Flows in the last 12 months: two of the first generation, and one Flow Gen 2. I lost the Flow Gen 2 while riding the bicycle just one month after I bought it, because the silicon strap is not as safe as the leather/plastic strap of Flow 1st gen.

    The two Flows 1st Gen have serious issues: one is reading the NO2 all over the place, very very high, and the second does the same with the PM2.5 and PM10. And there is no way to reset them. So they are not reliable in the real world.

    My AtmoTube Pro instead, which I carry with me on my bag every day since more than 1 year now, is still reading the PM2.5, PM1 and PM10 very accurately (I know this because I can I compare with other air monitors that I have at home like the Uhoo, PurpleAir, iQAir and others). It is therefore more reliable than the Flows, but it does not have a NO2 sensor and doesn't have the very helpful map feature.

    Also, I have been writing to the Flow team about the issues with my Flows, but they don't care to reply, so I am not trusting this company anymore. Not to mention that the Flow 2 costs now 199 Euro when it used to cost 159 Euro until just a month ago. That's too expensive now. Too bad because I really would like to have a Flow monitor that can work properly, because with its features I find that it would be a perfect air monitor if it worked properly.

  2. Remco
    November 18, 2019 at 9:59 pm

    Biggest question remains unanswered: how accurate is it?

    • James Frew
      November 19, 2019 at 9:42 am

      There was a discussion about this over on our YouTube review of the original Flow.

      "if you want to compare devices that might be the best way to measure the comparative accuracy.

      Defining accuracy down your specific movements and locations is tough, but I did reference it against local governmental air pollution data, and other open-source or crowdsourced information. The Flow was within reasonable boundaries of that data.

      It also depends on what your intent for using the data is. Ultimately, there are very few use cases where you will need to know, to incredible accuracy, the particulate matter in the air around you. So, you should be aiming for a reasonable approximation that allows you to monitor the air, and importantly, the changes in air quality around you."

  3. Richard T
    November 18, 2019 at 5:27 pm

    The Flow 1 device is now also able to export data too.

    • James Frew
      November 18, 2019 at 5:34 pm

      Yes, it was a feature released to coincide with the launch of the Flow 2, but is available in-app.