I was concerned about air quality during the sanding of my wooden projects. I use N-95 respirators and HEPA air purifiers for safety, but I couldn’t quantify the air quality to see whether my safety measures are adequate. Eventually, measuring air quality became a topic of interest. Let me share my findings.
In addition to using a Festool dust extractor, I have one of these Winix air purifiers near my wood-sanding area. I noticed that it catches not only fine wooden particles but also some dust.
While cleaning the filters according to the manufacturer’s instructions, I was glad to learn that the dust they caught ended up in the filters rather than in the lungs, so I placed quite a few of those HEPA air purifiers around my house.
This particular Winix model is two feet high (60 cm) and comes with a remote.
I also got an air quality monitor that measures fine particulate matter (PM, <2.5 microns in size—PM2.5), formaldehyde, and TVOC (total volatile organic compounds).
This model shows PM measurements in mg/m3. The included instructions provide the PM2.5 Level Interpretation table based on HEPA standards.
The reported values in mg/m3 may be different from the “Air Quality Index” which may be calculated differently.
I found that HEPA filters help with smoke too: the current outdoor air quality in California is pretty bad due to the fires caused by recent thunderstorms and lightning. The outdoor air quality index reached “Very Unhealthy” and even “Hazardous” levels in September 2020. Even though doors and windows are shut closed in my house, smoke traces still find a way inside, especially during windy days. I noticed that having the indoor air purifiers running 24/7 keeps the indoor air quality index almost always 0.
On windy, heavy-smoke days when the outdoor air quality index rises above 200, thanks to my air purifiers, the indoor air quality index never exceeds 5-7, which is still considered “good”.
The Sun is barely shining through the smoky air at 1:00 PM on 11 September 2020. Location: San Jose, CA.
Dust particles in the air are very small but they still differ in size greatly. Measuring a number of particles of 2.5 and 10 micrometers is a standard practice but other sizes of particles can be measured too by using a particulate concentration sensor designed by relying on the laser scattering method. Such sensors are capable of continuous acquisition and computing the number of suspended particles per unit volume which is also the particulate concentration distribution.
I got a M5Stack PM2.5 Air Quality Kit that is based on the ESP32 microcontroller and a sensor (PMSA003) from Plantower. This device can measure 0.3, 0.5, 1.0, 2.5, 5, and 10 microns (micrometers). It can be used to monitor air quality as is, or programmed using Arduino (or other platforms) to extend its functionality.
Other sensors are available for DIY integration with various microcontrollers.
Equipped with this knowledge, sensors, and air purifiers, I can quantify the air quality and make decisions to reduce my family’s exposure to harmful PM air pollutants. Measuring air quality with my own sensors on demand allows me to get more accurate and more up-to-date readings compared to weather apps and online websites that show air quality data; also, it gives me flexibility in measuring and comparing the air quality indoors, in the garage, and outside.
I think it is important to be mindful of indoor/outdoor air quality, to avoid going outside during bad days, and to ventilate homes during good days. Stay safe. Search about air pollution online to learn more about the topic. I would recommend starting with this article: Why is PM2.5 often higher than PM10?
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