Are Cheap Particle Counters Accurate?
When I first started making DIY purifiers, the particle counters I could buy were a US$260 Dylos or crazily expensive particle counters that costed thousands of dollars.
Since then, the market has exploded with new particle counters as cheap as 99 RMB. But are they any good?
Putting Particle Counters to the Test To get to the bottom of it, Smart Air tested three popular particle counters on the market: the Dylos DC1700, the Origins Excalib-AIR, and the Air Care.
#1 Dylos
The Dylos is the trusty particle counter Smart Air has been using since 2013, since it passed our previous test.
#2 Excalib-AIR
The Excalib-AIR is the popular, more technologically savvy device.
#3 Air Care
And the Air Care is a fancier version, including a large screen, richer information, pollution forecasts, better user experience, and even a CO2 monitor.
The Government Comparison Test We put the machines outside the Smart Air office on Dongzhimen Waidajie for six days. We compared their numbers to the official PM2.5 numbers from the government PM2.5 monitor at the Agricultural Exhibition Center about 1.3km away.
Results The first three days had pretty normal levels of air pollution. All three machines tracked the official numbers pretty well.
The next three days had extraordinarily low PM2.5. That’s helpful because concentrations in homes — where most people use particle counters — are below outdoor levels.
On these low-pollution days, the Excalib-AIR was a bit low.
Who Scored The Best? Here’s how each machine compared to the official numbers.
Dylos DC1700 vs. Agricultural Exhibition Centre PM2.5 R2 = 0.803
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We combined all the days and calculated the correlation of each machine with the official PM2.5 numbers.
All the machines correlated very highly. For non-nerds, 0.98 is incredibly close to identical! The Dylos had the lowest correlation at r = 0.90, but still incredibly high (and similar to our previous test).
Average Deviation Another way to measure accuracy is to look at how far the numbers were from the government data on average.
The Air Care had the lowest error, and the Dylos had the highest error. But all three were off by less than 10 micrograms on average.
The Airpocalypse Test To test accuracy at extremely high concentrations, we burned a cigarette in a closed 15m3 room. We managed to get the concentration above 1,000Âľg/m3!
Our comparison standard is the industrial Sibata LD-6S (red line), which is designed to handle extremely high concentrations.
The Excalib-AIR and the Dylos had a hard time keeping up with these toxic levels of concentration. In contrast, the Air Care was able to measure values over 1,000µg/m3. The Air Care won this test, although the chance you’ll need to measure values this high is slim.
Take-Home Message Overall, the three particle counters were reasonably accurate compared to the government machines. In the estimation of the Smart Air team, all of them are suitable for giving an approximate AQI value. Of all three, the Air Care scored the highest, with the lowest deviation from the government machines in both outdoor tests and the highest accuracy in the “crazy bad” test.
Usability Since all three machines are reasonably accurate, the question then really comes down to: How easy it is to use the device? And what features do they have?
#1 The Dylos (2710 RMB)
The Dylos easily loses this fight. It has no phone connectivity, and downloading the data is a terrible pain—and that’s if you have one of the old school pin connecter cables.
#2 The Excalib-AIR (654 RMB)
The Excalib-AIR is a solid entry-point particle counter. It gives reasonably accurate results with a simple interface. It’s not feature rich, but it does what it says on the box.
#3 The Air Care (1480 RMB)
To our eyes, the Air Care offers the best features. Besides particulate, it can measure: CO2 Temperature Humidity What can we do with CO2 levels? CO2 is important because CO2 can build up to dangerous levels if you have lots of people in a small space. Air quality experts also use CO2 as a hint of indoor air pollution. If you have sources of air pollution (VOCs like new furniture or remodelling, high CO2 levels will suggest that VOCs are building up too.
The Air Care also has other helpful data: Past 24 hours of AQI and CO2 for indoors and outdoors Pollution forecast When to open or close windows
Bottom Line: All three machines are accurate enough to use. The Air Care edged out the others in accuracy.