A few months ago, element14 and Renesas provided me with an air quality sensor (the ZMOD4510) that allowed me to perform a series of tests in and around my home and garage to get a better understanding of what affects our air quality here.
I had originally set out to test how the air quality in my garage might be affected by a car coming and going, and whether extra ventilation might be recommended. I was also curious to see how an attached garage might affect the air quality in the house itself.
The results were very surprising!
Surprising Results: My Cars vs a World of Cars
Going into this I was almost certain that my own cars would cause major air pollution in my garage, and most likely also in the areas inside the house near the door to the garage. After all, my own cars expel exhaust right by my own garage.
As it turns out, however, air quality is affected MUCH MORE by factors outside of my control. Wow! Plot Twist! While my car does create a minor blip in the air quality graph, the pollution caused by traffic and home heating in surrounding areas has a much bigger effect that far outweighs anything I do.
Now I'm also wondering if the smaller blips that I attributed to my cars coming and going might've actually been due to the open garage door letting in polluted air from outside?
This is one of those classic cases where individual changes do not affect outcomes, but group changes do. Unless the individual change is to move far away from civilization into the middle of a forest somewhere 
In case you were wondering, after my previous reports of the outdoor air pollution levels rising significantly during a cold spell, things have since returned back to much nicer levels - similar to the first readings I was taking in my home office. This is the tail end of it - at its highest point the ozone readings were up in the 40s.
It Really IS In The Air Tonight! (and also all day long)
I also found it interesting to see that my personal air quality could be affected by wind direction. That does make sense, given where I'm located with respect to surrounding urban areas, forested areas, and ocean areas, but I had never really given it much thought before. That's also something to consider when choosing a place to live - a small town near a large city might actually have air pollution similar to the city itself.
On the bright side, even the worst air quality readings I was getting here, at my house in Comox, are still very much in the safe and clean range, which makes me feel more comfortable about the area we live in, as well as knowing that I don't need to worry too much about our cars causing excessive localized pollution. I still recommend having a bit of ventilation in the garage though - I keep the garage window open a crack at all times.
Limits of Specific Air Quality Testing
I do need to point out that I was only testing a small targeted portion of common pollutants. The ZMOD4510 only checks for pollutants from combustion, namely nitrogen dioxide and ozone. The software that Renesas provides uses that information to also calculate the EPA standard air quality index (EPA AQI), as well as a quicker proprietary "Fast AQI" which I found very useful for my relatively short term testing.
Having seen the invisible for that small slice of the air has made me curious what else is lurking outside and inside my home. I wonder what the levels look like for VOCs (including formaldehyde, gasoline fumes, paint fumes, and offgassing from new carpets and plastics), carbon monoxide and carbon dioxide, dust, smoke, pollen, and do we have that dangerous radon gas here? (I think I'm safe in Comox, from what I've heard). I'm probably missing several other types of pollutants!
I'd be interested to try out some of the other air quality sensors Renesas has available (especially the zmod4410 for indoor air quality).
So even if this sensor says the air quality is great, it is still a good idea to use proper ventilation and filtration for homes and businesses.
Limits of Single Sensor Short Term Testing
My testing was also limited to a small slice of time and space - to get a more complete picture of where pollutants originate and where they are going, I would need to install a network of sensors all around the valley here and track all of that data over the course of at least a year, and ideally longer.
Isn't that always the way? Once you get a small taste of knowledge, it gets addictive and you want more!
Interpreting Results, Optimizing Personal Air Quality
This air quality testing project makes me wonder how I should approach air quality inside of my home - should I be checking outdoor air quality before opening windows for fresh air? Is "stale" indoor air worse for me than than the sometimes polluted air outside?
To keep the dust and pollen levels in my home to a minimum, I'll keep running my filter fans - this challenge thankfully also let me know that the "ionic/electrostatic" elements do not actually create extra ozone - that in itself was a really nice bonus bit of knowledge I gained from these experiments!
Maybe I should invest in a filtered air exchange system, so that outdoor air pollution does not contribute to poor indoor air quality. At the very least I'd avoid all that dust and pollen! The cats will probably still demand to have an open window once in a while 
Thoughts about EPA AQI Monitoring
Another interesting take-away from using the Renesas ZMOD4510 air quality sensor and the included software is that air quality is not really looked at as a moment in time, but as a general exposure level over time. That's why it takes so long to get a proper AQI result - the algorithm requires many readings to be taken over a long period of time - I think it's 1 measurement per hour for the EPA AQI.
What that indicates to me, and I may be wrong, is that in general it's not a terrible thing to get a short dose of pollution as long as the exposure is not prolonged over a period of hours or days. So while it's not pleasant sucking in a big cloud of smoke from a passing car, it's good to know it (probably, hopefully) won't kill us on the spot 
One of my more recent days of monitoring shows it really well.
In this chart the pollutant levels vary a fair bit throughout the day, but the EPA AQI (dark blue line) gives a nearly constant level.
Because the AQI levels change so slowly, I have generally focused on the ozone numbers throughout this experimenting, as they gave a more immediate indication of what the air quality was doing, but it was also interesting to see how the fast AQI and the EPA AQI generally followed and smoothed out the results.
Final Thoughts
I really enjoyed this project!
- It was just the right amount of building, coding, and experimenting to be fun while not being overwhelming, and also still a good workout of those coding/building skills. The Renesas library and sample sketch really helped with that too.
- It provided me with information that is normally hidden, invisible, to the average person, which I found really very interesting.
- And... AND... it gave me a totally surprise PLOT TWIST! Who doesn't love a good plot twist?
So, in summary...
I'm going to need more sensors! 
Thanks, everyone, for joining me on this journey!
-Nico
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As a Final Wrap Up, Allow me to quickly summarize my 7-week journey through this In The Air Tonight challenge:
Garage Air Quality Monitoring - The Journey
Sept 26
Having just received the kit, I posted my 1st blog post, Introduction, to introduce my plans for this challenge. I thought it would be a fairly straightforward test with fairly predictable results. Turns out I was wrong!
Sept 30
In my 2nd blog post, First Tests of the Evaluation Kit, I tested the ZMOD4510 air quality sensor with the provided communication board, to get a feel of how the sensor works and what the results look like.
Oct 13
For blog 3, Testing the HS4000-EVK, I wanted to test the HS4000 temperature and humidity sensor, but unfortunately I was not able to get the included HS4000-EVK software working. I was also unable to find any Arduino samples or libraries for it. Luckily the air quality algorithm does not totally depend on super accurate temperature and humidty numbers in order to give useable results, so I was able to continue without it.
Oct 17
In Blog 4, ZMOD4510 on Arduino, I connected the ZMOD4510 sensor to my own Arduino MKR WIFI1010 board, and was able to easily install the library and sample software provided by Renesas to start seeing air quality measurement results directly from the sensor. This was a pivotal moment in this challenge, as it gave me the freedom to use the sensor data in my own ways from there on.
Oct 22
Blog 5, Sending Sensor Data to NodeRed, is where I created my own sketch to bring the air quality data from the sensor to my Node-Red server, via MQTT, to see air quality data on my own UI in a browser.
Oct 25
With Blog post 6, Storing Data and Adding Graphs, I finished up the software set to store the air quality data in an InfluxDB, cleaned up the UI a bit, and added a graph. With this, I was able to start taking some real measurements for the next phases of the challenge.
Oct 27
(blog post 6 and a half?) I then spent a fair bit of time (Im-)Patiently Collecting Data
Oct 30
For Blog 7, Testing the effects of an ionic air filter, I tested the effects of running ionic air filters in my home office to see whether the ionic/electrostatic filter elements produce ozone as I've often heard in the past. Thankfully they did not.
Nov 4
For Blog 8, Air quality monitoring in my garage, I tested what happens to air quality as we use our cars. I accidentally also tested a few unexpected scenarios and realized that perhaps our own cars don't affect our air quality as much as everyone else's cars
Nov 8
For Blog 9, Monitoring the Outside Air, I tested the air outside of my home, and saw wide variations in our air quality that depended on whether the wind was coming to us from the city or from over the ocean. We also happened to have a short cold snap that provided some additional interesting results.
Nov 14
This was my 10th blog for this challenge, the summary!
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