Zooming out – NO2 Pollution

It hasn’t been a long time since one of the AQ monitors that I have, the uHoo, activated the NO2 sensor and helped me realize that the air quality isn’t so good regarding the levels of Nitrogen Oxide inside my house. I had to do some research and find out if the sensor was right and where this NO2 comes from.

Mainly, NO2 is produced by road traffic and energy production like power plants, with that in mind I began investigating. It wasn’t an easy possess, I had to consider many factors.

Firstly, I thought the source of this particular pollutant NO2 was the neighbors’ cars as early in the morning they will all go to work and some of them they will turn the engines on and they will wait till the engines are warmed up enough to set off. The buildings in my neighborhood create a U and cars are parked inside that U where the NO2 could be trapped temporally until it enters inside the houses, through the windows or escapes. Partly, I was right some spikes of NO2 were registered by the sensor at this time of the day. Source #1 was found but unfortunately the NO2 wasn’t high only at that time of the day, so I had to search further.

Screen Shot 2017-11-12 at 16.29.45
Buildings forming a U

Next, I analyzed the topography of my area. I had to find all the possible sources because I wanted to understand it as good as possible. A highway is very close to my neighborhood, about 650m but we are separated by a natural hill. I am not able to hear any road noise but I guess some pollution finds its way here depending the weather and wind conditions. Source #2


Screen Shot street no2
Highway A7

Then I had to see the greatest picture and with some further examination I was able to find all the factories / power plants in my region. There are quite many as you can see on the map below. My city Almeria doesn’t have as many factories as Sevilla for example but here is produced a enormous quantity of vegetables and fruit as a result the transportation is quite active. Source #3

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Industries across Andalusia

Finally, the winds can bring a great amount of NO2 from as far as 300km away. As you can see from the animated GIF below, in Gibraltar were many boats enter into the Mediterranean sea a huge concentration of NO2 is created there. Source #4


no2 graph


By starting super locally inside my bedroom I was able to zoom out and see the whole picture of the air pollution and how it expands. It is amazing how the pollution can travel long distances and reach our lungs. This is the reason we have to raise awareness globally. Regarding the sensor, although the NO2 values that the sensor took weren’t very precise, due to the lack of calibration, the device was able to detect the fluctuations of the pollutant and alert me. This is a domestic or an office device and I think the results are expected because you can’t compare it with a laboratory instrument that cost thousands of dollars. The importance here is the value that the device will bring to the user, and it is substantial.


17 Air Quality Apps

Not everybody can afford an AQ Monitor or simply not everybody wants to spend money on a AQ Monitor. That’s fine because here are 17 Free/Paid apps for you to check the outdoor air quality in your area. Some of them can notify you when the Air Quality is poor and guide you on breathing cleaner air. Unfortunately some apps don’t support some regions, this is because some developers face difficulties to obtain data from local authorities. (The public air quality stations in my region suck!)

CALIOPE (Free) ♥♥♥


Caliope is an air quality forecast system for Spain, developed at Earth Sciences Department of the Barcelona Supercomputing Center – National Supercomputing Center (BSC-CNS). The app supports all Spanish regions and the website version supports most European countries. Available data O3, NO2, SO2, PM10 and PM2.5. Maps and Pollutants. The website is available in English and Spanish.

EPA AIRNow (Free) ♥


The EPA AIRNow was designed by the United States Environmental Protection Agency. Although the agency has access to all the US AQ stations and a huge amount of data, the app is plain and with a very poor design. There is nothing special about this app. Even the icons are pixelated. They should be ashamed, the app looks like an internet page from 1999.

AirVisual (Free) ♥♥♥♥♥


AirVisual provides a free app for their device Node/Pro but it also works without it.  You can have access on a huge amount of outdoor AQ Stations around the globe. With a history browsing for all the pollutants, maps, ranking and news. The data are from public stations but also from their devices around the globe.

Wunderground (ads) ♥♥♥♥


Wunderground is basically an advance weather forecast app but they also provide air pollution data if you are lucky enough, which means depending the weather station they use to get the data for your area. If the weather station in your area has air quality sensors then they will provide you with the data.

Plume (Free) ♥♥♥♥


Plume Labs has design this app to help people avoid air pollution. Their app offers an air pollution forecast. It is a simple but a complete app. You will see an Air Index at the home screen, weather conditions and the activities that they recommend you to do depending the air quality at that time. They use public AQ stations but they will also combine the data from their devices in the near future. It supports notifications.

CleanSpace (Free) ♥♥♥


CleanSpace focuses on Carbon Monoxide air pollution. On the home screen you can see the “current” air pollution from your device but if you don’t have a device you can also browser their air pollution map. They also provide some weather data from the local weather station. A bit limited on the pollutants.

Air Quality (Free) ♥♥♥♥

Air Quality

The app exist on the app store with 2 different icons but the same name, by the same developer and the same interface. It is a very nice app with plenty of data. The app has some nice animations and a clean design.

Airpocalypse (Free) ♥♥


This app is for the Chinese citizens because only supports Chinese cities. Super Clean design and some funny icons and quotes.

BreezoMeter (Free) ♥♥♥


BreezoMeter will help you get to the point of the air quality immediately. They support a map but the elephant will let you know if your outdoor air quality is safe and it will give you some advice. It will also tell you which is the dominant pollutant in your area.

Netatmo (Free) ♥♥


Netatmo is mainly a weather forecast app but it also provides some simple air quality data. Nothing fancy regarding the air data.

Air Bubbles (Free) ♥♥


The Air Bubbles app indicates the air quality with colour-coded bubbles. Not many info available.

Air Matters (ads) ♥♥♥♥♥

air matters

Air Matters provides air pollution data, weather data and allergy data. If you suffer from allergies from a specific tree or plant like mugwort or olive trees etc, it will provide you with all the useful data. History browsing is also available and maps. Very clean and good design.

Awair (Free) ♥♥


Awair has a small and basic tab with the outdoor air quality and weather conditions which allows you to compare them with the indoor air quality in case you  have their device.

Air Checker (ads) ♥

Air Checker

Air Checker is very simple, you just type your city and it tells you the air quality plus the pollutants. I compared the data with others and they didn’t correlate at all. So I am not very sure about the accuracy.

Aerium (Paid) ♥♥♥


Aerium is a weather forecast app but if you upgrade the free app it will also give you air quality info.

Kaiterra (Free) ♥♥♥


Kaiterra is a free app for the Laser Egg 2 but it also provides outdoor air quality data. Simple design with an AQI and a histogram for the air pollutants.

Foobot (Free) ♥



Foobot has a basic tab with the outdoor air quality index for the outdoor location of the indoor device.

Air Quality Monitors – Comparison 2017 Q4

Holidays are coming and people are searching for gifts or for ways to protect themselves from air pollution. A great way to start 2018 is by seeing the air around you. Once more new companies offer more choices to the costumers and the old ones offer mature products through solid updates. On this update I have removed the Design row and I have added the Application Programming Interface API row, for those who want to know if the companies support this feature. Click on the image and download the PDF document.

comparison air 2017 Q4


  • Prices may vary during time.
  • Some Companies don’t specify on their data sheet if their devices are capable to measure PM2.5 or PM10 and they just mention the word dust.
  • Some other companies say: Our product goes beyond CO₂ by analyzing substances that directly affect your well-being by measuring VOCs. They aren’t clear if their devices have CO₂ sensor.
  • Some of the devices are AQI Monitors and Air Purifiers Combo. On this list you can only read the features as an AQI monitor.