I've been noticing how Simple Air Sensors ( #simple-air-sensor) will pick up fog from a humidifier, and have had a lot of success working with both adults and kids at events using a humidifier with these sensors. Because the #plantower sensor in the Simple Air Sensor (same as in the #purple-air) is triggered by fog, and because fog dissipates so quickly (and is safe to breathe), it's a really effective demonstration of the sensors reacting to the presence of a source of air "pollution" -- even though it's not really pollution.
It's interesting because people ask if it's because the fog droplets are in the 1-10 micron size range, and if that's what's causing it to detect them.
It's also really useful to show how the sensor has limitations -- that it can't tell the difference between a water droplet and a particle of air pollution.
Finally, the fog can be directed with a light breeze from a fan, and objects can even be placed in the path of the wind, shielding some sensors but not others. So with several different simple air sensors, you can kind of roughly simulate (at a small scale) the dispersion of an air pollutant in a real-world environment.
I'm interested in how this could be useful for any of the following:
planning the placement of sensors on a site
running a group activity to train people in placing sensors, whether this type or more expensive ones
discussing the limitations of different types of sensors
discussing how airflow affects readings
Finally, I was interested in getting some Simple Air sensors to run with a running average over 1 minute, rather than reporting every second -- to help demonstrate how some sensors only give the aggregate reading over a period, and so can miss moments of high pollution.
What do folks think of all this? Ideas or feedback? Thank you!
This could be a great way to plan where to put your Simple Air sensor! You could build a mini model of the area you'd like to study with something as simple as a series of tissue boxes. These boxes could model the way wind is blocked if you put your Simple Air Sensor between buildings.
You could play a game where one group sets up the humidifier and fan while the other group is our of the room and has to guess the location of the humidifier and fan (pollution source and wind direction) based on the data logs showing when the Simple Air Sensors went off.
This is a cool idea esp. the site-planning with "buildings" or air barriers. I heard a good comment about this on Instagram too, where i'd posted -- about using some flat partitions of clear material (acrylic) so you can see through them but the fog is blocked. (https://www.instagram.com/p/BzHJvaAHVff/)
@Warren I think this is an interesting way to show movement of fog droplets (10-20 um diameter, https://images.slideplayer.com/13/4090314/slides/slide_2.jpg) particularly if the fog can be seen moving (e.g., San Francisco Bay). Also, aerosols include both suspended solids and liquids so this model may be valuable for solids as well. However, liquid (fog) has different adsorption, absorption and surface tension characteristics that the particulates we traditionally measure and so would react differently (e.g., condense on surfaces) when moving through varying topography (e.g., buildings).
I wonder if the cocoa powder that @Stevie has tried might be a teaching tool with the fans and sensors. The message being that we can be exposed to fine particulates (PM2.5) that we can smell and detect with an instrument, but can't see. Perhaps baby powder (or another aromatic powder) might also be useful.
I love the idea of using cocoa powder or powdered sugar to model this (out doors of course!).
Yes, and the aromatic baby powder is nice because you can smell it. Great idea. We're going to try prototyping this activity soon. With 3+ sensors, would this be an interactive activity that would help in talking with community members about sensor placement?
Actually, the NASA team ( #aren) we're working with is interested in this, and they do classroom and informal science education. We may be able to work with them a bit on this at the GLOBE meeting in Detroit in a few weeks.
Great @warren : My responses,
1. planning the placement of sensors on a site:
a) The site can be Indoor places(schools, office or outside space, balcony). check the power supply for the Sensor unit(power bank, it is fine else use a socket). Inside the house, test nearby kitchen, garage, balcony.
b) Make it a drawing activity of the site and check for ventilation, door, rooms, chimneys, etc and place sensors in different places and test the readings.
2. running a group activity to train people in placing sensors, whether this type or more expensive ones
a)The orientation of the sensor plays a vital role in measuring air particulate matters. Ensure there is enough vent for air to pass through the outlet. (Make this as an activity, in which axis PM values varies).
b)Make this a paper or cardboard drawing activity for casing the Sensor unit Test with Casing and non-casing the sensor unit
c) Ask people to investigate on other particles that cause Air pollution(they would come with Smoke, C02, No2, etc and talk about Sensors that could measure these particles. This would lead to self-investigation of the various sources of air pollution discussing the limitations of different types of sensors
3. discussing how airflow affects readings
a) Keep sensor unit near a Ceiling fan(with & without Dust particles), Table fan, Door top dust, humidifier, or substances like Smoke, paper smoke, Agarbatti, Perfume to test the Airflow and change in PM values for different substances.
b) you can even test by spraying or splashing Water/Rain (which in a way flow of air) from a distance of 2-10cm from the sensor unit to see if there is any change in the Particulate Matter values.
c)Add Temperature & humidity sensor to check if it affects Airflow and PM values.
4. Sensor Value for an average period of time
a) Add delay(60000); in the first line of void loop() to display value after 1 minute.
b) Use Ctrl + shift + L (serial plotter) to, make it a Graph.
d) Via Serial monitor, copy all the values and use Spreadsheet to find average values.
e) Connect over ESP8266 and Wifi to transfer data over Cloud and check for 1 minute once in Thingspeak easily.