Build a low-tech air quality sensor?
The hackAIR cardboard sensor is low-cost and easy to use. You expose the cardboard for 24 hours, and then analyse a macro-photograph of the jelly to calculate pollution levels in the hackAIR app.
Cardboard offers a crude measurement. Estimates of air pollution by particulate matter are therefore only given at three levels: low, medium and high.
Assemble the sensor
1. Cut open the drinks carton and fold it open.
2. Cut one or several square pieces of about 5×5 cm size.
3. Along the diagonal axis of the pieces and near the center, make two small dots with the tip of the pencil.
4. Along that same diagonal axis, bend the surface slightly outward.
5. Make a hole in the upper-right corner and tie a thread through it.
6. Do the same at the lower-left corner, and attach a small weight to it (a paper clip, coin, pen).
7. Use the buttering knife to apply a small amount of petroleum jelly on the surface of the carton. Spread the jelly as evenly and smoothly as possible.
All you need is the hackAIR app on your phone.
Measure air quality
- Place the sensor outside with the test surface facing windward, and sheltered from rain. Ensure that the sensor doesn’t touch anything.
- Expose the sensor for a full day (ideally 24 hours), then retrieve it.
- Place your smartphone with the macro lens on top of the two pencil marks on the sensor. Read the manual of your lens to see which distance is required.
- Take time to let your mobile adjust focus, then capture the photo, using flash when necessary.
- Open the hackAIR app and upload the photo.