Aqara TVOC Sensor (review)

When I think of sensors, the word ‘Aqara’ usually springs to my mind, first due to the almost complete set of sensor devices that they manufacture – motion, contact, leak, vibration, light, smoke, and of course the ubiquitous temperature and humidity combos you see everywhere. Now the company have moved forward with a sensor to measure Volatile Organic Compounds or VOCs for short – the new Aqara TVOC Sensor (TVOC = Total Volatile Organic Compounds).

What are VOCs?
Volatile organic compounds (VOC) are organic chemicals that have a high vapour pressure at room temperature. High vapour pressure correlates with a low boiling point, which relates to the number of the sample’s molecules in the surrounding air, a trait known as volatility.

VOC’s are responsible for the odour of scents and perfumes as well as pollutants. VOCs play an important role in communication between animals and plants, e.g. attractants for pollinators, protection from predation, and even inter-plant interactions. Some VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Most VOCs are not acutely toxic but may have long-term chronic health effects.

You would typically find that sources for VOCs in the home are from fresh paint when you redecorate, cleaning products like polish, rubbing alcohol or bleach, or even new furniture, where chemicals have been used in the processing of the fabric or wood.

Aqara isn’t by any means the first company to make a TVOC sensor of course, with both Kaiterra and Eve making devices that either contain a TVOC sensor or are have a TVOC sensor as the core of the product. I’ve had the Eve Room (V1) for a few years now, which gives data for VOCs, temperature, and humidity and it has served me well, even though it does get through batteries like Alan Partridge got through Toblerones (Google ‘Alan Partridge’ and ‘Toblerone’…). The Eve Room V1 also has no screen and uses Bluetooth, so two disadvantages are clearly evident here. To see what the Aqara TVOC sensor brings to the table, read on.

PACKAGING

The TVOC sensor is, for what you get, quite reasonably priced (it’s currently on Amazon.de for just under €50) and can be found in a few online stores in Sweden. By contrast, the Eve Room (v2), is selling for practically double the price, and as of the time of writing, still uses Bluetooth. Putting that topic to one side, the version I have here today is the Chinese version, hence the packaging sporting most of its text in Simplified Chinese.

As with all Aqara products these days, the packaging outlines the features with neat little icons.  This includes the device using Zigbee 3.0, intelligent linkage (as it’s smart), different mounting options, temperature & humidity sensors, an E-Ink display, and a TVOC sensor. So, just like the Eve Room, the TVOC sensor’s E-Ink screen provides excellent contrast between the text/imagery and the background, compared to a standard LCD display. The display can also be read at much more acute angles than a typical LCD display.

The contents of the box all centre around the sensor itself, being the parts to help you mount it, although it can just be stood on a shelf if you prefer. Aside from the sensor is a manual in Chinese (there is one in English too), you get a magnetic plate and a matching double-sided adhesive sticker. The magnetic plate can be fitted to a wall with either the sticker or the two included pin-tacks. The circular magnet sticks to the back of the Sensor so that it can attach to the magnetic plate.

THE TVOC SENSOR

I’ve had the sensor for around 5 months now, but when it first arrived, I was actually quite surprised at how small it was, which I’d describe as roughly the size of two boxes of matches lined up side by side. The official measurements are 41.6 x 76 x 14mm / 1.64 x 2.99 x 0.55in (H, W, D). Aside from the clear plastic screen, the rest of the device is white plastic. The screen itself is a lot smaller than the main body, at 48 x 24mm / 1.89 x 0.94in (250 x 122 px), and is surrounded by a large white border, with just the Aqara logo at the bottom. It may not matter to many, but I’m happy to see Aqara placing their logos on their products in a much more subtle way than some companies do. After all, it’s not like you need to advertise the brand in your own home.

The screen shows a standard set of information, which can be switched to one of three different display modes by simply double pressing the button at the top of the device. one of the modes has the top portion of the display showing the TVOC readings using five instances of a ‘leaf’ icon, with 5 ‘dark’ leaves being excellent air quality and five ‘clear’ leaves reflecting the worst-case scenario. The second mode shows much the same information, but the icons have been replaced by numbers for the TVOC density. The third mode simply shows the temperature and humidity, with no mention of the TVOC details.

To the left of this information, there’s a small icon that shows that the device is linked to an Aqara hub and functioning correctly. In the first two modes, the bottom half of the screen is made up of the temperature and humidity readings. Somehow I feel the TVOC readings should be more prominent than the latter two, as its main role is to report on VOCs. So, if I had a say, the TVOC display would take up two-thirds of the screen, with the temperature and humidity numbers relegated to the top 1/3rd of the screen.

The sensor uses two CR2450 coin batteries, which should last at least twelve months. To get to the battery compartment, there’s a small slot on the base that can be pulled open by hand – unless you have no nails like me…

Both sides of the sensor feature slats that allow air in, so as to permit the sensors to monitor the temperature, humidity and air quality. The top of the device features a button, although its main purpose is to pair the device to an Aqara hub, change the display mode, or confirm its link to said hub. That’s essentially it in terms of its appearance!

IN HOMEKIT AND THE HOME APP

The TVOC sensor in HomeKit is much like most other sensors in that with the arrival of iOS14, practically all sensors were removed from the tile section of the Home app, and placed above and collated into sections. This unfortunately means seeing the readings involves going into the relevant ‘circle’ and tracking down the appropriate sensor to check its readings. I can still see the logic, but I’m not sure it helps when you have a heap of sensors throughout the home. This is not the fault of the sensor of course.

When you do get access to the individual tiles, you can dive into them and get a little more detail. Each of the three sensors shows the battery level for the device, and show the relevant basic data – temperature levels, humidity percentage, and Air Quality along with VOC density.

If you’re already familiar with HomeKit, you’ll be aware that as of iOS 14, the Home app still doesn’t make it easy for you to create automations based on temperature or humidity levels. The TVOC sensor (and any ‘Air Quality’ sensor for that matter) is an exception. For the TVOC sensor, you can create an automation based on whether the air quality ‘rises above’ or ‘drops below’ a set level. These levels are fairly general, which are broken into five descriptive sections labelled Excellent, Good, Fair, Inferior, and Poor. You would also find this with Air Purifiers like the Smartmi P1 and the Vocolinc PureFlow for example. So, if you have an air purifier with a filter that can remove TVOCs, then an automation telling the purifier to turn on, based on the readings from the TVOC sensor, would be one example of how it can be used with other HomeKit devices.

IN THE AQARA HOME APP

As you can imagine, there’s more to the sensor when viewed in the Aqara app. You get the same basic details on the main page for the sensor, although the battery level isn’t shown in any detail, so I guess the Home app has a slight advantage there. There are the usual set of options on the settings page, amongst which you’ll find details on the device’s Zigbee signal strength.

Where the Aqara app adds value is via the data it accumulates for practically all its devices, so in the case of the TVOC sensor, you have graphs showing readings over 24 hours or 7 days. You can also get a log of any changes to all three sensors on a day by day level. You can also view any of these graphs in landscape mode.

You can set the TVOC sensor to show one of two settings regarding the measurement for VOCs, as well as switch the display to Fahrenheit or Celsius.

Even though potentially high levels of VOCs can’t do much harm in the very short term, you could have an ongoing problem, that the source of the issue hasn’t been identified, so it’s good to keep an eye on things with the options for graphs. However, should you experience sudden high VOC levels, you may want to jump on things to find the source, and a good way to do this within the Aqara app is with push notifications. This saves you from glancing at the sensor’s display every few minutes.

These push notifications allow you to set the conditions under which a push alert is triggered, which includes the levels at which they should trigger, and the time of day or days of the week. You can also set a standard push notification, or set a custom one for yourself.

PERFORMANCE

One thing I’ve generally been disappointed about with my original Eve Room is that due to it using Bluetooth Low Energy, it would only report back to the app roughly every 10 minutes, so even though VOCs in the room aren’t exactly the kind of thing you want instantaneous notifications on (it’d still be nice though), to check the Eve app to see any reporting back of a spike in VOCs is really only a way to look back on what occurred rather than what’s happening. Of course, the Eve Room v2 solved this with a built-in display, like the Aqara, so this is welcome on both devices.

In our home, without going into too much detail, we have two dogs, with one of them a rather elderly Beagle, adopted by us after spending much of his life in a testing facility, and so the combination of these two ‘factors’ means we regularly have to ‘clean up’ after him, which involves using rubbing alcohol. This alcohol spray sends all of our TVOC sensors crazy of course, including the Aqara model, so from this basic test, I know that it definitely works. I’ve got a total of three sensors in the home – the Aqara, the Eve Room v1, and a non-HomeKit device by Xiaomi, which contains all manner of sensors, including a TVOC sensor, and all of them react, although with the Eve Room, I have to check the data in the Eve app (I’ll update to V3 when they finally add Thread…).

Does it compare in terms of the readouts? Yes and no. What I’ve noticed is that the way the TVOC count is displayed in the Aqara app seems to be at odds with the way my Xioami unit shows; so the Xiaomi device might, for example, show a reading of 2.7mg/m³, whereas the Aqara sensor would show the reading as 0.27mg/m³. This suggests to me that somehow, whilst it’s working, there’s a bug that is displaying the readings with the decimal point in the wrong place. I did wonder if it could be that the Aqara sensor was correct, but it’s hard to fully determine, as the Xiaomi device shows mg/m³, whilst the Eve device shows readings in PPM (parts per million), and it’s not clear from a quick Google search if these measurements are comparable (1,400 ppm = 1.4mg/m³). If someone has a simple and definitive answer, please let me know! I can live with that if it’s accurate, and so far it seems to be, when comparing the Aqara to both of the other sensors, with the exception of the point just mentioned.

What’s not working in the app, is that you have the option to switch between mg/m³ and PPB (I assume Parts Per Billion), but the graphs in the app never switch, instead, staying set at mg/m³. This is not the case “on-device”, so the sensor will show either PPB or mg/m³, depending on what you’ve set in the app. It’s only a minor thing to me, but it does need fixing. As regards temperature and humidity, they seem to be almost ‘spot on’ when compared to the other sensors, although when you first install the sensor, it will take a while to settle and start reporting accurate data.

One other oddity is that when it comes to sampling the air for any of the three sensor values, there seems to be no set period of time that it checks; in the early hours of the morning, for example, there was a sample reading taken at 01:49hrs (41.1% humidity), then another at 04:03hrs (40.3% humidity), and third sample reading at 06:47hrs (41.8% humidity). I can only assume that it’s taking these sample readings only when there is a change of at least half a percentage point, in terms of humidity in this case. It’s important to note that the sample points are different for each sensor, so it doesn’t take one random sample reading for all three sensors at the same points in time, which goes closer to backing up my guess that sample readings are taken when the sensors detect big enough changes.

WRAPPING UP

Other than the previously mentioned issue, I’ve not noticed anything out of the ordinary, and if nothing else, the battery life being at 88% after 5 months of use seems pretty good, so the estimated one-year battery life is selling its longevity a little short. As for the design of the product, whilst it fits with the general aesthetic of most other Aqara products, and even seems to have garnered a couple of design awards, I personally find it a bit bland and underwhelming, design-wise, mostly when it comes to the display. It’s not like I’m going to be looking at it all the time, to be honest, but I’m a fan of the colour display of the Xiaomi product, despite it not being HomeKit compatible. I’ve also had zero connectivity issues with this device, which is usually my experience with Aqara’s Zigbee products, so that counts for a lot, although even with a disconnection, the screen will still show you any issues, regardless.

The bottom line for me is that at half the price of the Eve Room (which currently uses Bluetooth until they update it with Thread), the Aqara is probably a better purchase.