PM2.5 and VOC Emission in 3D Printing
It is well known, like many other processes or equipments, 3D printers emit fine particles and VOC (volatile organic compounds) during operation. My 3D printer is in my living room and I have always been careful about which material I print (only PLA and PETG) and I always kept an air purifier next to it which turns on automatically at maximum power when I power the 3D printer on. However, I am not sure quantitatively how problematic the emissions are and how useful the air purifier is. To study this, I conducted a small experiment measuring the amount of fine particles (PM2.5) and VOC.
Although I tried to be careful conducting the experiments described in this post, since it was done at home not in a lab, using readily available consumer grade sensors not lab equipment, the results should be interpreted with caution. Naturally, this post cannot be used as an health advice.
All the experiments are done with a Prusa MK3.9 printer with Prusament PETG filament. The filament was new and its original package is just opened.
3D printer stays inside a modified Original Prusa i3 MK3 ENCLOSURE using an IKEA Lack table. The modification is I have only the left and the back side closed with plexi. The front and the right side is fully open.
On the right side of the printer, I have a Philips AC1214/10 Air Purifier which has both a HEPA and an Active Carbon filter. I run the Air Purifier at its maximum/turbo setting.
I am using the following sensors:
Sensirion SPS30 particulate matter (PM) sensor that I purchased as SEK-SPS30 evaluation kit.
Sensirion SGP40 VOC sensor that I purchased as SEK-SVM40 evaluation kit.
Both sensors are connected with the cables in the evaluation kit to a Raspberry Pi 4. The sensors are mounted on the top of the printer, underside the IKEA Lack table.
I collect PM2.5 and VOC index data from the sensors every second, and send them to Graphite which keeps a time-series database. I visualize the data with Grafana. In the figures below, I used a moving average (5 mins) filter for PM2.5 values.
It is possible to collect different PM data with the sensor but I am collecting the mass concentration (ug/m^3) of PM2.5 particles which are defined as particles having size between 0.3um and 2.5um. The reason for this is that PM2.5 is very often used as a benchmark for the effect of fine particles on health.
I also collect the printer status every 10 seconds from the PrusaLink API.
PM2.5 and VOC Emissions
The figure below shows the PM2.5 and VOC data collected when the Air Purifier was mainly turned off (until 11:45 or so).
PM2.5 data shows the baseline was around 2 ug/m3 and with 3D printing it increased to 3 ug/m3. When the air purifier turned on, it decreased back to 2 ug/m3.
The peak in VOC index is when I cleaned the 3D printer bed with Isopropanol (IPA). This is also a good test to see if VOC sensor is working. VOC index has to be around 100 (the orange dashed line), this is the baseline. The VOC index decreases as IPA evaporates and mostly stays around or under 100. So the VOC output from 3D printer is actually not much visible.
The figure below is another example of air purifier not running.
Like before, PM2.5 number increases from a base level of above 1 ug/m3 to over 3 ug/m3. VOC Index shows a similar pattern as before. It takes around 20 mins to go back to baseline after cleaning the bed with IPA.
Now lets see a full run with air purifier running.
Not surprisingly, it keeps the PM2.5 level at baseline between 1-2 ug/m3 and VOC index just below 100.
While I was doing the last test, I was cooking something. The kitchen is not very close but still it is possible for air to reach the 3D printer easily. I realized during cooking, the other air purifier I have in the living room close to kitchen showed ~150 ug/m3 for PM2.5. Later, I wondered if the sensor over 3D printer catched anything, and yes it did !
As you can see, PM2.5 measurement peaked to 60 ug/m3. By accident, I also tested if the PM sensor is working.
First, I should reiterate, this experiment is not controlled, done with uncalibrated equipment and only with a single type of filament. However, I think it still has some validity, at least in my environment.
It can be easily seen 3D printing increases PM2.5 concentration. However, the increase is quite small. WHO recently (2021) updated their recommendation to keep PM2.5 exposure to below 5 ug/m3. I always measured under 4 ug/m3.
The change in VOC measurements is negligible during 3D printing. However, if you stay close to the printer, you can definitely smell a smoke/gas, thus obviously there is an emission. An overall VOC number might not be very meaningful. Some compounds are more toxic than others. It is not possible to assess this without advanced equipment. However, as far as I know based on research articles, PLA and PETG are the least toxic filaments.
It might not be a must but an air purifier definitely decreases the PM2.5 concentration and probably helps to keep VOC levels low.
I think every 3D printing environment, particularly ones in living environments, should be equiped with air cleaning systems. This is a simple and effective improvement.
PM2.5 and VOC sensors are not expensive but I think there is no 3D printer with such sensors embedded yet. I think it could be quite useful to have them, at least as optional accessories.
PM2.5 is not the full story. There are also ultra-fine particles (UFP), defined as smaller than 0.1um in size. I am not sure if there is any consumer grade sensor that can measure them yet.
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