SeeTheAir AQ Monitor v0.1

Have you ever been in a situation where you wish you had had a device tailored to your needs? Over the years I have reviewed various Air Quality Monitors but each time they lack something which will make them unique to me. Don’t get me wrong each device has its features and characteristics, some of them are amazing and some of them not very useful. As a result, I decided to build my DIY AQM. I couldn’t have done it without Electronza and Teodor Costachioiu help with coding, he is a brilliant coder/engineer. I absolutely recommend you to check his blog you will find a lot of interesting projects.

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“See The Air” & “Nicholas and his incredible eyesight” Books

“See The Air”

Years of experience and personal research made me write and design this straightforward guide-book about air pollution. All the crucial information are inside this book, see the air you breathe today. Available on Paperback and Digital.

“Nicholas and his incredible eyesight”

Nicholas is a Scottish boy who will help your kids understand better what Air Pollution is and what they need to do to combat it. Through his empowering story he will teach them how to be more sustainable and thoughtful with the environment. Available on Paperback, Digital and Limited Edition Hardcover.

“Nicholas – The Science Book”

Let’s make a journey around the world and learn everything about the air we breathe. We are going to learn about the Earth’s atmosphere, the composition of the air and the most common air pollutants. In addition, we will learn how air pollution negatively affects humans and the environment. Available on Paperback.

uHoo a Portable AQM?

The idea of having an Air Quality Monitor anywhere you go seems good especially when you can have 9 sensors with you. So here is a tip on how to convert a stationary IoT indoor AQ monitor to a portable one, in this case I will demonstrate it with the uHoo because I really want to measure some NO2 and O3 concentrations in some busy spots of the city.

There two ways to do that, one of which isn’t easy but bear with me.

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Cheap Face Mask, Worth it?

Over the years, I have reviewed some very good face masks on See The Air like the Cambridge Mask and Vogmask. The only backward is the price especially when you have to buy them frequently because you wash them often and you wear them a lot. There is a solution by using masks such as the AirGo which allows you to chance the filters and the neck warmer is durable and washable and the O2 Canada Respirator which allows you to change filter easily. However, I wanted to try a cheap and lightweight face mask for the summer which will cost around $3 and it will have the ability to use exchangeable filters because I want to be able to wash it once a week.

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Air Pollution – Wrong Approach

Over the past few years, I have been tweeting and posting messages on social media platforms about air quality and pollution issues around the globe and I have noticed that the more severe the message the greater the response from people (likes and/or retweets). The same technique is being used by newspapers and magazines to achieve greater impact.Read More »

Indoor IAQ Monitors 2019Q2

Here are all the available IAQ Monitors on the market. This time and after your help I have included many more information in a Google Spreadsheet document which you are going to appreciate a lot, such as website links and whether the device has been reviewed on my blog or not yet. There are so many devices out there but they all lack innovation and they all offer exactly the same technologies. Companies had better hear users feedback!

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PurpleAir-II vs Luftdaten

A USA air quality monitor in comparison with a DIY German air quality monitor. How well do they perform with each other? Full disclosure, the software the monitors run is developed in the mentioned countries. The components from both devices are made mostly in China.

  • We already know PA-II’s correlation of coenficency R²≈0.87 with the corresponding FEM GRIMM and FEM BAM.
  • The SDS011 sensor which is most commonly used in the Luftdaten project has a correlation of coenficency  ≈0.84.

The PA-II features a double PMS5003 laser sensor. The PA-II module averages out the values from the two sensors, so in case one of the two sensors registers unexpected high readings, (perhaps some dust or insects etc) this technique makes the readings less questionable. The Luftdaten DIY project as we have mention above mostly uses one SDS011 laser sensor. However, the Luftdaten software supports many PM2.5 sensors including the PMS5003 series among others.

Analysis

My friend Ashley from Plume Plotter has already done a comparison between the Purple Air PA-II, the Luftdaten SDS011 and DEFRA for a complete year of data link.

First of all, by comparing PA-II’s two identical sensors we can see on the graph below that the Sensor B has the tendency to register higher concentrations over time, on my device, maybe another device has a different behavior. So the process of averaging out the concentrations from both sensors has some positive results.

Many scientific papers insist that the PMS5003 and SDS011 sensors are nephelometers and not particle counters. Which means that they are influenced by humidity. Nephelometer comes from the compound Greek word nephelo “Νέφος” which means cloud.

I live in an area with high humidity. Right now the official RH is 83%. The PA-II registers 51.6μg/m3 and Luftdaten 38.3μg/m3. The difference between them is huge. However, both devices are mistaken. Purely for your information the humidity sensor in the Luftdaten device measured RH 94% the PA-II measured RH 53% and AirVisual measured RH 72%. From my experience, I would say that the relative humidity is definitely above 80%.

From the graph below we can see the same results. The PM-II overestimates the PM2.5 concentrations most of the time in comparison with the Lufdaten sensor. Both devices seem to measure the same fluctuations over time so there is some correlation. The humidity that day started low at RH 30% and climbed up to 60% at the end of the day. There is an influence between humidity and how the sensors and especially the PA-II measure PM2.5 concentrations without any doubt.

PA-II Luftdaten 4-02-2019
SeeTheAir: 24h PA-II & Luftdaten side by side

Conclusion

The conclusion that I get from my everyday readings having the two devices side by side and from Plume Plotter’s analysis is that the PA-II overestimates the PM2.5 concentrations especially when relative humidity is above ~55% while the Luftdaten’s readings are more adjacent to the official readings.

Screenshot 2019-02-02 at 18.52.14.png
Plume Plotte: Regression lines for Luftdaten sensor and Purple Air PA-II sensor readings vs. actual (reference instrument) concentrations.