Are Cheap Particle Counters Accurate?

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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 Laser Egg, and the Node.

 

#1 Dylos

 

 

The Dylos is the trusty particle counter Smart Air has been using since 2013, since it passed our previous test.

 

#2 Laser Egg

 

 

The Laser Egg is the popular, more technologically savvy device.

 

#3 Node

 

 

And the Node 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 Laser Egg was a bit low.

 

Who Scored The Best? 

Here’s how each machine compared to the official numbers.

 

 

 

 

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 = 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 Node 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 1,000µg/m3!

 

 

Our comparison standard is the industrial Sibata LD-6S (red line), which is designed to handle extremely high concentrations.

 

 

The Laser Egg and the Dylos had a hard time keeping up with these toxic levels of concentration. In contrast, the Node was able to measure values over 1,000µg/m3. The Node 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 Node 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 Laser Egg (654 RMB)

 

 

The Laser Egg 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 Node (1480 RMB)

 

 

To our eyes, the Node 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 Node 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 Node edged out the others in accuracy.

Paddy graduated in aeronautical engineering from Bristol University, and now runs Smart Air’s operations from Beijing. He’s an advocate for open data, free information and transparent business.

2 thoughts on “Are Cheap Particle Counters Accurate?

  1. Hi, is Wifi required for these counters?
    If Wifi is on, can’t they just search your location and get the “official” readings for your area to improve average accuracy.

    I understand you did a test with cigarette particles, but it seems many sensors are accurate when it comes to cigarette particles, but not necessarily with all types PM2.5 particles.

    For example here is a cheaper sensor that seems to pick up cigarette particles pretty accurately:

    https://www.youtube.com/watch?v=cBJWWbxChds&lc=z22juhvappqiufvzl04t1aokgwfhhyg14q03jw4dknrfbk0h00410.1534648389218361

    But I’m still skepticle PM2.5 paricles are being measured properly.

    Thank you!

    1. Great questions Jai! None of these counters require WiFi to work. First off, the Dylos doesn’t connect to WiFi. The Laser Egg and AirVisual both connect; the Laser Egg connects in order to store your historical data on your server, and the AirVisual in order to pull outdoor AQI for the nearest station to you. Both work without WiFi no problem.

      Your question on whether or not these types of counters are accurate only for cigarette particles can be answered by the first test in the article, the ‘government comparison test’. Here we compared the readings from the devices with the readings from the government, more importantly we were comparing measurements for outdoor PM2.5 in Beijing. The results were really accurate for all machines, which makes it clear that they do measure PM2.5 well!

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