Citizen Science Air Quality – First tests with the Air Quality Eggs

In a previous post some early tests were performed on one of our two Air Quality Eggs. This post will continue that process but show the two of them together.

Here’s a picture of the two Liverpool FoE Air Quality Eggs (AQEs), which I’ve named Tweededee and Tweedledum!


In this mode they are static AQEs, connected to power, monitoring local air quality and reporting NO2, CO, temp and relative humidity to the opensensors data store every 4 seconds. Below is a picture of the pair of Eggs reporting their data taken 17 November 2016 at 15:32 GMT.


This picture shows one of the challenges of devices such as this. The two Eggs are next to each other but Tweedledee is reporting an NO2 figure of 44 ppb, whereas Tweedledum is reporting 63 ppb.

Investigating this further, the photo below includes another AQE that I have had for a year or so. Again it’s in the same location and picture was taken within minutes of the photo above.


Tweedledee now reads 52 ppb, Tweedledum 74 ppb (a similar delta), whereas the other AQE on the right gives a reading of 22 ppb. The temperature, Carbon Monoxide and Relative Humidity figures are all identical or very close. It’s the NO2 numbers that have some variation.

There are various technical answers to this variation in the data. The Eggs were calibrated before they were shipped, but it’s possible that they need re-calibration, which is not a simple process at all. The key lesson for this project is that individual points from these sort of sensors should be treated with caution.

Before moving on this can be investigated a bit further. Below is a chart that shows the temperature readings for Tweedledee and Tweedledum from 12 November 2016 to 14 November 2016. As above, the sensors are indoors and next to each other. The blue line is Tweedledee and the orange line Tweedledum.


The chart shows the temperature readings slightly differing, but they definitely move in step with each other. The correlation of these data sets is 97% for those who like those sort of statistics!

The final chart in this post is for the same 2 Eggs and the same time period, but this time the data is the NO2 readings from each Egg.


The top line is Tweedledum and the lower one Tweedledee. The chart shows that Tweedledum consistently reports higher than Tweedledee. The movement of the two data sets is harder to see, but they do appear to move in step. The correlation between the two data-sets is 69%. Detailed technical transformations to analyse this data further will not be performed beyond this. The key point from these tests is that the data is potentially valuable, but individual data points should be treated with caution.


Citizen Science Air Quality – early tests of the Air Quality Egg

A previous post has reported that we have recently received the 2 Air Quality Eggs that are part of the Liverpool Friends of the Earth Citizen Science Air Quality Project. I have used these Eggs before, but there are some new features with these devices, which are important for this project – specifically they offer:

  • GPS for location tracking and so we can go mobile with them; and
  • an onboard SD card for local data storage to complement the mobile data capture

After the unpacking the first stage in the project process is to test them and make sure they are going to be fit for purpose for our volunteers.

The initial set up connects to my WiFi and data is reported to openSensors. Without too many hiccups the Egg is reporting data. The validation of this is not pretty, but is a format like the screengrab below, which shows the Egg reporting Carbon Monoxide, Nitrogen Dioxide, Temperature and Humidity (just off-screen): opensensors

Once data is flowing it’s then useful to do some sense-checking on the data and also check the new features i.e. GPS and the onboard storage. So I took the Egg on a trip into Liverpool. During the journey, the Egg is powered by a battery and stores data on the SD card. This data was then later downloaded for analysis.

The picture below shows this data imported into QGIS – an open source GIS package – for analysis.


The GPS appears to be working fine. This was indeed the route taken, using a mix of bus and walking. You can see the larger spacing of the readings when the bus is moving at speed.

The colour coding used is just a spread of the data. Work to be done later is to determine the appropriate colour coding according to national guidance from health agencies and other expert bodies. For now, the colour coding simply shows the spread of data – with dark red being the highest values and white the lowest. The legend in the top right shows the schema and the associated numbers in parts per billion (ppb) of NO2. These figures should not be used in isolation. There’s always the possibility that an individual sensor is faulty or there is some other issue. Confidence comes with increased numbers of sensors and consistent readings over time.

One of the challenges that the test revealed is more about the physical side of the egg than the electronic and information side. We’re going to have to think about how someone can carry the egg, because it’s more bulky than the AirBeam PM sensor. We also need to make it a bit more weather proof and probably buy 2 portable batteries for our 2 sensors when they go mobile.

First tests are looking good though. Next is to get the other Egg up and running, do similar tests with it and then also do some comparison tests to see if these two eggs report similar data. I can compare these two to my other Air Quality Eggs that I’ve got from previous work over the last few years. More on this later.

Citizen Science Air Quality – the other sensors arrive

For this project we wanted to test two different sensors.

We’ve already received the AirBeams that measure Particulate Matter. These two sensors are undergoing testing before we can give them to volunteers. Unfortunately we had a problem with one of these PM sensors and so we are waiting on a replacement to come from the USA.

The other sensor we decided to use is the Air Quality Egg. Importantly, this sensor measures nitrogen dioxide and so provides us with data on this critical air pollutant to support our view of PM from the AirBeams. The AQE sensors are a new model which has GPS and local storage. I’ve used Air Quality Eggs in my own house for several years and so I’m comfortable with how they work, however there will be some uncertainty and learning with this new kit.

The Eggs were caught up in customs from the USA, which meant we had to pay some additional customs charges before they were released.


We paid the customs charges and finally, on 27 October 2016 we received the Eggs. Here’s a photo from the first opening:


Those who are technical minded might be interested in the photo below. It shows the latest Air Quality Egg (on the left) that Liverpool Friends of the Earth has procured for this project. On the right is one of my personal Air Quality Eggs. A lot more technology has been packed into that same case over the last few years. Great work by the guys at wicked device.


Now the Eggs are here I can start testing them. First things first though: stick a label on it!


More updates to follow as testing progresses

Citizen Science Air Quality – problems with one of our sensors

As discussed in previous posts we have received our 2 PM sensors – AirBeams –  and the first steps in our process are about setting them up and then testing the sensors as preparation before we engage with potential volunteers.

Unfortunately we’ve hit a problem. One of our sensors (and we’ve only got two!) has a problem. This didn’t appear straight away. Both sensors were generating readings in line with expectations and all seemed fine. However one of them (unit #1) seemed to have a problem with its power. It would work fine when connected to the mains supply, but stopped working on battery.

At this stage the AirBeam simply wasn’t powering up at all without a power connection. Our supplier – HabitatMap – have been great and offered excellent support. Together we began investigations to figure out what was going wrong and how to fix it.

Here’s a photo of the opened up AirBeam. The temperature and humidity sensor is the upright white “thing”, the particulate sensor is on the other side of the board to the left.


The final stage of stripping the AirBeam is shown below. This allowed us to get access to the battery. We swapped the existing battery (not shown here) with another battery we had in and sure enough the unit powered up. You can see the red light showing the unit running off battery power.


So we knew there was some fault with power, but was it a faulty battery or a problem with charging?

The photo below shows us charging up the existing AirBeam battery. If the battery wouldn’t take a charge for some reason, then we could focus in here and get a replacement battery swapped in.


When the battery was fully charged we put it back into the AirBeam, reassembled everything and did further tests. These tests led us to the conclusion that the battery is fine, but there is a problem with the charging mechanism in the AirBeam. Therefore we are sending this unit back for replacement or repair. HabitatMap have been great and will reimburse our postal costs.

So we are left with only one PM sensor for now. Our guess is 2-3 weeks for a new one to arrive, but let’s wait and see.

Although it’s frustrating, this was the point of the testing phase. Things do go wrong with technology and it’s better to pick these things up now, than impact the experience with volunteers. This technology is still pretty new!

Air Quality Citizen Science project – early testing of the PM sensors

Following on from previous posts describing the PM sensors that we are using, the next steps are about testing them before giving them out to volunteers.

This post will describe some of these tests and also give some insight into what data is generated and how it can be used.

Some simple trips with the sensors allow me to capture data and make sure they are working as expected. The data that is captured is stored on the phone (android smartphone) and can be later uploaded to the aircasting website or to any other source. The aircasting website is a community mapping development by HabitatMap and provides a form of crowd-sourced data. An example of this is shown below and can be found hereaircasting_map

Beyond this pooling of data in a community map like the aircasting website, it’s also possible to look at individual data streams. This was part of the testing process for our AirBeam sensors. The data from one trip with one of the sensors (unit 1 for reference) is shown in the diagram below:


This shows a single trip in south Liverpool near Allerton Road. The individual data points are visible, with a simple colour coding according to the spread of the data i.e. green are lower values and red are higher values: this does not necessarily mean that red is unhealthy however, it’s just a higher reading.

The diagram below shows the same trip and data but zoomed it for one part. The reading for one data point is also shown. This reading was taken on 13 October 2016 and the PM reading was 13.12 micrograms per cubic meter.


At this stage I will not go further into how this data can be used. The purpose of this post is simply to share some insight into the testing process. A goal of the project is to find out how this data can be useful to individuals and community groups – at this stage we just want to make sure the data is being generated and that it looks in line with expectations. The journey above supports the view that this sensor is working as expected.

More to follow on testing.

Air Quality sensors: first steps to set them up

A previous post announced the arrival of our first two #airquality sensors. These two sensors measure particulate matter (PM); we are still waiting on delivery of two more sensors, which will measure nitrogen dioxide.

Now we’ve got these sensors, the first steps in our project plan are about setting them up before they are ready for use by volunteer participants. We also need to do some proper testing, but more on that in another post.

Below is a picture of our two AirBeams to measure PM:


For the technically-minded the AirBeam is based upon the Arduino Leonardo. In addition to the particulate matter sensor inside the case, there is also a sensor to measure temperature and relative humidity. The AirBeams are battery powered and charged using a USB cable. These AirBeam needs to be used with an Android smartphone and a specific “app” has been developed for their use – the “aircasting” app is found here.

The AirBeam connects to the Android smartphone using bluetooth technology. The Android smartphone is primarily needed to provide a GPS location for the data that is recorded by the sensors. Additionally the microphone of the phone can be used to record local noise levels – potentially providing some insights into local noise pollution levels, although this is not the immediate focus of our project.

The screenshot below shows the aircasting app and the readings from the sensor. So, at this point in time (readings are taken every few seconds) PM was 6 micrograms (one millionth of a gram) per cubic meter. At the same time, relative humidity was 51%, temperature 60F and the sound level was 81dB. The colour coding can be configured and is designed to give a quick idea about current levels.


These readings update continuously and can be recorded on the smartphone for mapping or analysis. More on this in a later post.

Michael has been using this AirBeam for the last year or two and so is very familiar with its use. They are great devices, but of course have their limitations. One limitation is the need for an Android smartphone and so volunteers will need to have an appropriate phone for the sensor to work. This is a constraint, but we feel we can still learn a lot during the project.

More information to follow on the progress of our tests with these sensors and how the data can be used.

The first sensors arrive – unpacking the AirBeam PM Sensors

For our Air Quality project we have ordered:

The PM sensors are called AirBeams and were ordered from Habitat Map in the USA.

We ordered them 31 August 2016 and we’re glad to say they arrived a few weeks later. There were some minor customs charges, but at least we were underway!


Opening up the box and there are two lovely new AirBeams. which we promptly labelled with a Sharpie pen – Liverpool FoE Sensor #1 and Sensor #2 are here!


Next steps are to start testing and configuring these sensors in preparation for giving them to volunteers. We are still waiting on the NO2 sensors as well.


Air Quality in Liverpool


We are looking at air quality within Liverpool as part of our local efforts.

We are currently running a “citizen science” project. To do this we are grateful for funding from the Liverpool Clinical Commissioning Group.

This is a small-scale project with some simple objectives:

  1. We want to understand more about the different technologies that can be used to support citizen science initiatives around air quality
  2. We want to understand how these technologies, and the data they generate, can be used to help individuals and community groups.

No doubt there will be other learning along the way. For example, we are interested in how this sort of community-level engagement and “hyperlocal” data gathering can be used to supplement and complement city-level and national air quality monitoring and management.