Air Quality

29,000 people die prematurely in UK every year due to air pollution. It is the second biggest killer after smoking. A press release (PDF) (17th Oct 2013) by the World Health Organisation identifies outdoor air pollution as a leading environmental cause of cancer deaths.

We envisage an air quality monitoring system as being a useful safety device but, it also has applications in smart home automation. On detection of smoke or other pollutants a warning could be provided and windows and vents shut, to avoid it entering the house.

Existing Products

AirPi

AirPi
AirPi is a piggy-back board for the Raspberry Pi. It features sensors to measure temperature and humidity (DHT22), air pressure and temperature (BMP085), carbon monoxide (MiCS-5525), nitrogen dioxide (MiCS-2710), UV levels (UVI-01) and light levels (LDR).

Birdi

Birdi
Birdi is an Indiegogo project to build a very smart and simple looking smoke alarm, CO monitor, temperature sensor, etc. in one device.

Cube Sensors

Cube Sensors
Cube Sensors are six 'powerful sensors that help you live better'. They are basically remote sensors that you distribute around your home and they come with a Smartphone app. The full set of sensors cost around £400.

We aim to duplicate all of their functionality and more for around £60, by re-using existing capabilities and integrating the sensors fully into our smart home.

Netatmo

netatmo
Netatmo is a personal weather station with air quality sensors and has apps for iPhone & Android. It's a good looking piece of kit but, it is yet another 'smart' device that comes with apps and its own enclosed ecosystem. It comes as two modules, one indoor and one outdoor. It measure temperature, humidity and CO2 and air pressure. Interestingly, it also monitors sound levels.

Data Feeds

It should also be noted that there are numerous data feeds and sensors online, that can be used to provide useful data.

BBC Weather Data

We are already collecting local weather data as part of our weather project. The BBC 3 day forecast includes pollution and UV level information.

We have written a WeatherService java class that retrieves and stores weather information and then analyses it for useful insight. Certain values will result in notifications and voice announcements in our home.

The Department of the Environment measures outdoor air pollution using a Daily Air Quality Index, which is a scale from 1 to 10.

Sensors

Air Pressure Sensor

Atmospheric pressure is covered under our weather station project. This has been installed and the software written to read values from the sensors.

Carbon Monoxide (CO) Sensor

The MiCS-5525 is a carbon monoxide sensor used on the AirPi.

MQ-7 carbon monoxide sensor
We are using the MQ-7 which is a low-cost CO sensor that requires a 5V power supply. It provides an analogue output.

Hydrogen Gas Sensor Sensor

The MQ-8 is an analogue sensor for measuring Hydrogen gas levels.

Methane Gas Sensor Sensor

The MQ-4 is an analogue sensor for measuring Methane (CH4) gas levels.

Nitrogen Dioxide (NO2) Sensor

The MiCS-2714 is a nitrogen dioxide sensor (datasheet). It replaces the MiCS-2710 sensor used on the AirPi.

Hazardous Gas Detection Module MQ135

MQ-135 hazardous gas sensor
The MQ-135 is a hazardous gas sensor used for air quality control and is suitable for detecting NH3, NOx, alcohol, Benzene, smoke, CO2,etc. We have connected one to an analogue input board near our front door.

Implementation

This project is based around a Raspberry Pi configured as another remote slave HCS processor. It is re-using the same RPi as our Weather station project.

In addition though, some of the key air quality sensors are also duplicated within our home.

This image shows our test layout, with the components mounted on 3mm Perspex sheet. The analogue header board has various circuits and sensors connected to it.

Software

I2C

For the I2C connected devices we are using Python code and the Adafruit Python Library.

Dallas 1-Wire

For the 1-Wire connected devices we are using Java code.

Further Reading

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