For quite a while, the air quality monitors that have interested me the most have been portable devices. Not just because I think they can often be more useful but also because it feels like they’re much rarer than their indoor and outdoor mounted counterparts. Off the top of my head, I could probably barely name five portable (consumer-grade) air quality monitors. On the other hand, I am sure I could quickly list 50 indoor and outdoor air quality monitors.
Anyway, before I get too off-topic, this explains my excitement when Temtop recently reached out asking me to review another one of its devices. Until a few months ago, I had only heard of Temtop but had no hands-on experience with the device. However, after reviewing the Temtop M10+ a few months ago, I quickly understood why these air quality monitors are quite popular. While the M10+ was a solid device (and you can read my full review if you’re interested in learning more), it’s fair to say that I’m much more excited about the potential of the Temtop S1+.
So, what exactly is the S1+? Well, it’s a low-cost, portable air quality monitor that measures PM2.5, temperature and relative humidity. It also shows AQI, but this is not a sensor and is instead a value on an index acquired by knowing the PM2.5. It’s also worth noting that it’s not a full U.S. EPA AQI (based on many pollutants) but only an AQI based on PM2.5. Either way, portable PM2.5 monitors are relatively few and far between; therefore, I was intrigued by the S1+ – especially at such an affordable price.
I’ve been using the S1+ for about a month now and look forward to sharing my thoughts on the device. Over this month, I’ve used it in a range of situations – both in my home and while out and about – and I’ve also compared it to a range of other air quality monitors. If you want to learn more about this device, please read on! I’ll do my best to cover all pertinent aspects of the device and answer any questions you may have about it.
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Accuracy
One of the most interesting aspects of Temtop is that it creates its own PM sensors. While this might sound obvious, anyone familiar with air quality monitors will know that most sensors come from a few manufacturers. For example, AirGradient, PurpleAir and AirBeam all use Plantower sensors. On the other hand, AirThings and Air-Q rely on Cubic sensors. This makes a company that creates its own sensor technology quite unique. The only other company that comes to mind is IQAir, which has the AirVisual Pro monitor. Of course, this also often means the sensors tend to be less researched than their more widespread counterparts.
Since the Temtop S1+ only has a particle (PM2.5) sensor inside, my job is easy this time around. Unfortunately, to make it a little bit harder, no third-party testing organisations like AIRLAB, AQMD, or Afri-SET have examined any of the ‘consumer-grade’ Temtop sensors. With that said, AQMD has examined the Temtop LKC-1000S+ as part of its AQ-SPEC program, and the device performed very well in regard to PM2.5 correlation with reference-grade monitors.
While admittedly a more professional monitor, the good results of the Temtop LKC-1000S+ show that Temtop can develop good sensors. This is especially important in the case of this company, as its sensors are made in-house, and these results bring some trustworthiness to the brand. With that said, the consumer-grade monitors from Temtop, like the M10+ and S1+, use different sensors, and it will be interesting to see third-party tests of these sensors if they’re ever released.
Before doing any of my own comparisons, I was curious about the precision of the S1+. Since I only have one other Temtop monitor (the M10+), this is far from a good sample size, but I still wanted to try. I compared PM2.5 readings from the two devices over a couple of days. At both high and low PM2.5 concentrations, these devices exhibited very similar readings, and I was pleasantly surprised by the precision. At very low concentrations, I was surprised to see these two devices even frequently show values within 0.1 of each other. This makes a lot of sense as both monitors use the same sensor technology, just in a different shape (presumable the S1+ sensor has to be smaller to fit into the smaller body of the monitor).
Of course, this doesn’t prove accuracy, but it does show that the inter-device performance is good. The less variance between devices, the better, and while a larger sample size would be ideal, this shows that the sensors can show consistent readings. With this in mind, I want to discuss the device’s modes before looking at some comparisons with other devices.
When plugged in, the S1+ will take a reading every 1.5 seconds. When not plugged in, the monitor will take a reading every three minutes (in A mode) or five times every thirty minutes (in ECO mode). Interestingly, however, is that while ECO mode shows a 30 minute reading, you would assume this is a rolling average. Instead, it’s calculated by an ‘intelligent’ algorithm, and this is the value shown on the screen. While I don’t know how much I trust the ECO mode algorithms (more on this soon), three-minute intervals while on the battery are acceptable, but I wish there were also other options (such as 60 seconds or even 30 seconds). When plugged in, the device provides very frequent updates.
Now, I did want to run some of my own (far from scientific) comparisons with other low-cost air quality monitors, but I honestly couldn’t figure out how to do this very well. This is due to the fact that even when plugged in (and taking a reading every 1.5 seconds), you can only export data from the monitor in 30-minute increments. While this shouldn’t have proven to be a big issue, what made it so difficult is that this exported data isn’t simply an average but, instead, seems also to have some ‘ECO’ algorithm applied to it. Just look at the comparison graph below:
While I expect the AirGradient ONE readings to be higher than the true concentration (the Plantower PMS5003 is known to overreport PM2.5 concentrations at higher values), this is a very big difference and also shows how the S1+ can be slow to respond with ECO mode on (I shifted Temtop data back by one hour for this comparison, as the ECO mode, and, apparently, exported data have a significant lag). As you can see, the S1+ provides far lower peaks than the AirGradient device and, when not edited, with a significant delay.
It is worth noting that you won’t see this delay reflected on the measurements on the device’s screen itself (unless you’ve set it to ECO mode), but it does make running any kind of comparison frustrating. I did a similar comparison with the Temtop M10+, and the results followed far more closely. Below, you can see that comparison:
As you can see, the results in this comparison are far closer and more similar to what I would expect – even though the M10+ only exported data in 30-minute intervals too. I tried a lot of things, like applying different algorithms to the AirGradient data (like the EPA and CF=1 corrections), but both of these still led to much higher readings than with the Temtop S1+.
For the first time in any of my articles, I’m having trouble concluding exactly where the Temtop S1+ stands when it comes to accuracy. I do believe the device is accurate because it uses the same sensor technology as the M10+ (which is quite accurate compared to other consumer-grade monitors – see the above graph) and because, anecdotally, whenever I look at the S1+ next to my AirGradient and PurpleAir devices, they report quite similar concentrations.
At the same time, when I actually export the data from this device, it’s clearly being adjusted in a way that I don’t quite understand. I wish that either the export function would show every reading from the device, give an average over the set period (in this case, 30 minutes), or that the weighting method was explained somewhere. Even after some communication with Temtop, I’m a bit lost. Anyway, if I had to give a personal note, I would say the accuracy looks to be decent, but there needs to be more transparency with the device.
The Temtop S1+ also monitors temperature and relative humidity, and I wanted to see if these values were accurate. Not only can they be misleading if incorrect, but if Temtop uses either measurement in correction algorithms for PM2.5, it’s important they are at least somewhat accurate. Luckily, from what I was able to test, both temperature and RH values are surprisingly good – at least when the device is battery-powered.
Compared to my Traceable monitor, which has been lab-tested and proven to be very accurate at around 50% RH and 25°C (with decreasing accuracy as RH increases and decreases), I’ve found the S1+ to almost always provide very similar values. As I am writing this, my S1+ reads 23.5°C and 51% RH, whereas my Traceable monitor reads 23.5°C and 52% RH. While they don’t always read as closely as they are in this example, I’ve never seen the two deviate by more than 3% RH and .5°C.
Of course, it’s important to note that as relative humidity increases, the accuracy of both devices will drop. Therefore, if you live in more extreme conditions, you might want to run your own comparisons if possible. While I would love to do this myself, I don’t have a good device for testing the accuracy at higher humidities as even the Traceable monitor can become quite inaccurate at more extreme values.
Design
The S1+ is a compact device that measures 90x68x18mm – all in all, it’s a very small device! It’s also very lightweight but feels of decent build quality. While the device is all plastic, and I have scratched the screen a fair amount already, it doesn’t feel badly constructed at all and actually feels quite well-built.
At this size and weight, the device is both very easily storeable in a handbag or backpack, and it’s also comfortable to hold in your hand or even store in a pocket. As with all air quality monitors, it’s not water resistant and you will want to keep it safe. I would also recommend against storing it without a case, as dust can easily enter the sensor vent and interfere with readings. That said, I appreciate this small and seemingly durable form factor.
On the front of the device, you will find a large LCD screen that displays all information gathered by the monitor. While I am disappointed by the lack of a high-contrast E-ink screen like the one on the M10+, I understand that these screens are difficult to find in certain sizes, and it likely wasn’t a cost-effective choice for the much cheaper S1+. However, when viewing the devices side-by-side, it’s obvious how much better the M10+ screen is. That said, without seeing the devices side-by-side, the screen on the S1+ is perfectly adequate.
Thankfully, this device only has one display option, which allows you to see all information at all times. Unlike some devices where you need to scroll through different screens to see different information, the S1+ shows you the PM2.5 concentration, AQI, temperature and relative humidity all on one screen. Despite showing all of this information, the screen doesn’t feel cluttered, and I appreciate the layout, which also shows the time, status icons, and remaining battery life.
Since I’ve mentioned the status icons, we might as well discuss them quickly. Alongside the time, you can also see if the device’s alarm is on, which mode the device is in, and the remaining battery life. The mode can be adjusted with some buttons, which we will discuss in a second, but it’s worth emphasising that I think you will want to keep this device in A mode most of the time instead of ECO mode. If you skipped over it, please read my reasoning for this in the Accuracy section of this article.
At the top of the device are two buttons – a power button and a ‘settings’ button that changes the device’s mode. With only two buttons, the device itself has limited customisation, and more important settings are built into the app instead. I don’t mind this approach at all, but it means that if you want to use the S1+ as a standalone device primarily, you should at least download the app initially to set up the device according to your preferences.
On the left-hand side of the device is an intake vent, which allows air to enter the PM sensor for measurement. On the right-hand side of the device is an exhaust vent, allowing air to exit the device once the sensor has had a chance to measure the particle concentration. Also of note is that housed below this vent on the right-hand side of this device is a USB Type-C port, which can be used to charge this device. This device does not need batteries, as the internal battery is rechargeable. It’s worth noting that this USB-C port is only for powering the device.
On the back of the device, you will find some more venting (likely for the temperature and RH sensor if it’s not part of the PM module) and some regulatory information. There’s nothing of too much interest here, as the S1+ is quite a simple device – but that’s not a downside!
Overall, I like the design of the S1+, which leans toward being a portable air quality monitor that can also be used as a static indoor monitor when needed. While a monitor like the M10+ is better for indoor use due to the larger screen, better contrast, and more conveniently located Type-C port, the S1+ is much better as a portable monitor that can double as an indoor air quality monitor when needed.
Connectivity
The Temtop S1+ can send data to the accompanying Temtop app via Bluetooth. This app is a free download, and you will need to log in to use it. Thankfully, at least on iOS, there is an option to sign in with Apple, which I generally choose for privacy and security reasons (such as generating unique email addresses for each account). Users on Android will need to create an account with their email.
The app will also request location data, as it partially functions as a weather app that pulls in data from Open Weather. I assume this choice was made to try and make it a ‘one-stop’ platform for both air quality and weather, but I haven’t yet found myself opening this app or even caring about the weather information provided, as I have other apps for that purpose. With that said, I don’t see any harm in including this information, and some people may find it quite useful.
When you first open the app, you will need to add a device. In my case, I had already added my M10+ for my previous review, so I had to add an additional device. Luckily, this process is very straightforward, and all you will need to do is either scan the QR code on the device or manually enter the device information (this can be found on a sticker on the device). From here, I had to give the app permission to find local devices, and after naming the device, the setup was complete.
With these steps completed, the device now appeared on the home screen of the app, right underneath the weather information from Open Weather. Since I also have the M10+, this device appears below, and I can quickly access data from either device. One thing that always bugged me about the M10+ was that to access information from the device on the app, I had to first physically press a button on the monitor to enable Bluetooth. Thankfully, that is not the case with the S1+, and you can quickly view data without any additional actions needed on the device itself.
By tapping on the monitor, you will be taken to a screen that shows the four metrics recorded by this device – PM2.5, AQI, temperature, and humidity. These are all presented with a value, an icon, and some status text that indicates if these values are good or perhaps uncomfortable. Overall, I think this is a good presentation of the information and it’s easy to understand at a glance what your current air quality situation is.
By tapping on any of these metrics, you will be presented with a graph that shows data in 30-minute intervals, which can be scrubbed by just moving your finger along the graph. The app also stores data for a good amount of time (at least a few months), and perhaps even more interestingly, the device also has enough internal storage to store a decent amount of data. This means that even if you don’t connect the device and your phone frequently, you shouldn’t lose data as you can with some other monitors.
There is also an option to export data, which, while probably more useful for ‘power users’ such as myself, is always handy to have. While it is limited in usefulness due to only showing 30-minute intervals, I’m always glad to have the ability to export data, and I believe it should be an option with all air quality monitors.
In the settings for the monitor, you will be able to change a few basic settings of the device, such as the temperature units, AQI index used, time system, alerts, and a few other basic settings. Most interestingly, this section of the app allows you to calibrate all sensors on the device. While this won’t be useful for PM2.5 (unless you happen to have a reference instrument!), it’s nice to see this included for temperature and humidity. Finally, you can also receive OTA updates (which I haven’t seen yet) through this section of the app.
While the app is quite simple overall, it has all of the features that I consider essential and I don’t think it’s lacking anything major. While I would like to see finer resolution on the graphs, this is an issue with the modes on the monitor itself and not the app. I’m also happy to see more advanced features like data exporting and calibrations supported.
Pricing & Competition
Pricing is where the S1+ becomes such an interesting and competitive monitor. While most portable and semi-portable air quality monitors still cost at least $80, the Temtop S1+ comes in at a very reasonable price. Depending on where you purchase the S1+, the device should be around or under $50.
A price under $50 makes it a very competitive option, and it might just be one of the first monitors I can recommend in this price range alongside the IKEA Vindstyrka. It’s worth noting that there is also another variant of the S1+, the S1, which is the same monitor minus the connectivity (and, therefore, has no app support). This device also has a varying price range, but it might be worth considering if you are looking for a standalone device, as it should be even more affordable than the S1+.
Interestingly, at this price range, it also doesn’t have any competition as a portable monitor – at least not out of the devices that I’ve tried. While there are some other portable devices around this price range, I would be quite hesitant to trust them unless they have named components inside (which, to my knowledge, none do). Even when it comes to indoor monitors, the only real competition at this price point is the IKEA Vindstyrka, which also has a VOC sensor but lacks Bluetooth and portability.
Therefore, I think the real question here isn’t ‘Is this a good monitor for the price?’ but rather, ‘Should I spend more to get a more well-rounded monitor?’. As I mentioned earlier, you could spend around $80 to get the very solid and well-rounded Qingping Air Monitor Lite. While this device doesn’t have the same portability, it has a better range of sensors that some users will find more valuable. If you don’t mind spending a little more, you could even get the AirFanta G2, a portable option that also includes a CO2 sensor.
I can’t tell you which monitor is best for your case (at least not here, but feel free to share your situation on the forum, and I will do my best to help!), but if you are looking for a monitor for PM2.5, temperature and humidity, this is ideal. If you appreciate portability, even better! However, if you want a device that will primarily remain plugged in, the Qingping Air Monitor Lite might be a better choice. If you value having CO2 readings as well and don’t have a dedicated CO2 monitor, you might instead want to consider the AirFanta G2, which is more well-rounded, albeit pricey.
Conclusion
The S1+ is a decent PM2.5 monitor that I appreciate for the simple reason that Temtop is trying something new. There’s no other monitor on the market at this price point that I would trust to provide me with reliable PM2.5 readings. It’s also portable, which makes it even more compelling.
It does have some flaws, though. For example, I would love to have a way to make it take regular readings at much shorter intervals when on battery – let’s say every minute. While this would significantly decrease battery life, I would be okay if this was a balance that the user could choose themselves. There are times when I prefer a battery life of only a few hours, but with short measurement intervals. On the other hand, there are times when I would prefer a longer battery life and less frequent measurements. The key here, however, is that it should be the user’s choice.
This slow updating means that while it can be a portable monitor, it is only really portable in that you can take it with you to work or school and sit it on a desk to monitor the quality of the air you breathe. While the device does have some functionality when out and about, keep in mind that even after getting off your train, you might need to wait a few minutes for an updated reading. That said, this is a decent and low-cost option if you want a good PM monitor for your home. When it’s plugged in, it provides very consistent readings.
I’m also not a fan of the ECO mode, and I don’t really understand how it works or how exported data is manipulated. I wish Temtop would be more transparent about this, and I think it’s something that they need to work on. With more transparency and an update that allows the user to adjust measurement intervals, this would be a fantastic device! As it is, it’s a decent one as long as you know of its limitations. At the end of the day, it is very cheap!
I’m glad to see more affordable monitors (that are reliable) entering the market, and it’s great to see Temtop entering this segment. While they have been well-known for creating affordable monitors for a while, none are quite as affordable as this, and I appreciate having more options that are budget-friendly. I’m sure many readers will, too!
If you have any further questions after reading this article, or if you’ve tried the device yourself and would like to share some thoughts, please feel free to comment on this post down below. I do my best to reply to all questions and comments, and it’s invaluable to hear about others experiences with the device too. Thank you for reading this article!
- Very affordable pricing
- Compact, lightweight, and portable
- Decent accuracy for PM2.5 compared to other consumer monitors
- Good inter-device consistency
- Includes temperature and humidity monitoring
- Simple, easy-to-use interface with all data on one screen
- Rechargeable battery with USB-C charging
- App support for data tracking and calibration
- No CO2 or VOC sensor, limited to PM2.5
- ECO mode introduces significant lag in readings
- Limited data export with unclear processing algorithms
- Shorter battery life due to infrequent readings when unplugged
- Screen is prone to scratches and lacks high contrast
- Lack of transparency about data processing methods
Temtop S1+ FAQ
What does the Temtop S1+ monitor measure?
The Temtop S1+ measures PM2.5 concentrations, temperature, and humidity. It also provides an AQI value based on PM2.5 levels.
Does the Temtop S1+ measure CO2 or VOCs?
No, the S1+ is limited to PM2.5, temperature, and humidity. If you need CO2 or VOC measurements, consider other models.
How portable is the Temtop S1+?
The device is compact (90x68x18mm) and lightweight, making it easy to carry in a pocket, backpack, or handbag.
How accurate is the Temtop S1+?
The PM2.5 sensor is fairly accurate compared to other consumer-grade monitors. However, ECO mode can introduce lag in readings, and there is some uncertainty around data processing methods.
How often does the S1+ update air quality readings?
When plugged in: every 1.5 seconds
On battery (A mode): every 3 minutes
On battery (ECO mode): five readings every 30 minutes
Is the temperature and humidity data reliable?
Yes, temperature and humidity readings are generally accurate within ±0.5°C and ±3% RH under normal conditions.
Does the Temtop S1+ have Wi-Fi connectivity?
No, it connects via Bluetooth to the Temtop mobile app for data tracking and calibration.
Can I export data from the Temtop S1+?
Yes, you can export data, but only in 30-minute intervals. Additionally, the processing method for exported data is not fully transparent.
Have Questions or Comments?
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Temtop S1+ Review - The Most Affordable Portable Air Quality Monitor
A detailed review of the Temtop S1+, a budget-friendly portable air quality monitor that measures PM2.5, temperature, and humidity. Explore its features, accuracy, design, and limitations.
Product Brand: Temtop
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Pros
- Very affordable pricing
- Compact, lightweight, and portable
- Decent accuracy for PM2.5 compared to other consumer monitors
- Good inter-device consistency
- Includes temperature and humidity monitoring
- Simple, easy-to-use interface with all data on one screen
- Rechargeable battery with USB-C charging
- App support for data tracking and calibration
Cons
- No CO2 or VOC sensor, limited to PM2.5
- ECO mode introduces significant lag in readings
- Limited data export with unclear processing algorithms
- Shorter battery life due to infrequent readings when unplugged
- Screen is prone to scratches and lacks high contrast
- Lack of transparency about data processing methods
Start the discussion at forum.breathesafeair.com