UFP = Ultra Fine Particles. Paper from a year ago. My interpretation: Relax, we’re safe.
“Compared to other domestic sources of UFPs, the 3D printing using PLA had a similar UFP emission to cooking using an electric frying pan. Using ABS resulted in UFP emissions similar to those from grilling food on a gas or electric stove at low power.”
For me, it’s more about the VOC’s
I am as unconcerned about volatile organic compounds as about ultra fine particles.
If anything, there might be reason to be slightly (very slightly) more worried about UFPs due to the increased risk of crossing the blood brain barrier, and the increased likelihood of long term build up.
As I understand it, you get a higher dose of VOCs and UFPs both from candles. The dose makes the poison, and if it was more than a slight statistical shortening off the average lifespan, on a scale that is basically in the margin of noise, then it should have already shown up as a life expectancy difference between Catholics and similar religious adherents for whom candles are significant and frequent parts of worship, and non spiritual secular folk.
So I see it as basically the same trade-off as bacon or red meat. Eating this will, on average, reduce your lifespan, but will contribute to your enjoyment of what remains, and abstaining offers no guarantee that you will actually be part of the cohort displaying the statistical benefit.
A matter for individual choice, and therefore for transparency about the risks, but not a matter for immediate governmental regulation, except possibly where it involves at risk populations.
I would not recommend continual close proximity to 3d printing for pregnant women or small children. A lot of the same precautions that apply to soldering apply here. Be sensible.
I have yet to see any data that made those correlations with a candle. I have seen data that suggest that over frying mackerel is not healthy for the occupants of the surrounding area. Some of the VOC levels in that experiment can be found in 3d printing ABS, and that can go on for hours upon hours, sometimes days.
The research that I’ve read relates not only the level or total VOC concentration, but also the carcinogenic properties of the chemicals.
The research is still in it’s infancy at this stage so there is still allot we don’t know.
Perhaps it’s nothing, perhaps it’s as concerning as second hand smoke from cigarettes. (We now know that’s bad) but one thing if for sure, it’s a very complex and difficult thing to quantify.
You know… I read it somewhere, but I did not delve into it and confirm… so, here goes! (Full disclosure: I actually have no idea how credible the source was where I read that. Shame on me.)
Emissions of Nanoparticles and Gaseous Material from 3D Printer Operation, Yuna Kim, et. al., Environ. Sci. Technol., 2015, pp 12044-12053 says 1.61 × 10^10 ea/min, or 16 billion, with most (96%) of the particles being nanosize (<100nm). I could not find a full text, so I’m not sure what ea/min means here? I’m guessing either ‘each’, or ‘electrified aerosol’ based on searches on the machine involved. I.e. unit count of particles either way. Please let me know if you have better info, as if it means something else, that could drastically change the outcome of the comparison!
Characterization of Fine Particle Emissions from Burning Church Candles, Philip M. Fine and Glen R. Cass, Environ. Sci. Technol., 1999, pp 2352-2362 is a bit complicated, as it does not give a directly comparable value. It gives a burn time, grams burned, and a microgram per gram burned rate of organic compound emission. Taking experiment CAN-4D as a middle-of-the-road-ish rate and one of the ones with ‘neglible sooting’ (they say that sooting produces much larger particles, while normal burn is in the same <100 nm region as the ABS), it gives 1.65 mg burned over 15 min, or 76 µg over one minute.
The peak for normal burn in terms of frequency of size is at about 0.05 µm. n-hexacosane was the largest component of the extremely varied mix, (for paraffin candles as CAN-4D was), and a quick measure in Avogadro (a chemical modeling program) of 1-hexacosane gives the length as 32.975 Å (ångströms). So 15-hexacosane would give us about a 50nm long molecule (to serve as a proxy to convert between grams and eaches).
Hexacosane has a mass of 366.422552 g/mol, multiplied by 15. Divide our 76 µg by that, 13.83 or so nm, or 8.327×10^15 particles per minute.
So a quietly burning candle produces five orders of magnitude more particles (not specifically solely VOCs, though from what I could see in the list of particle types, it sure seems heavily weighted that way) per unit time than ABS.
So for the length of run-time issue you mentioned, that seems obviated by the five orders of magnitude. If a candle burns for an hour and the printer runs for ten, that accounts for only one of the five. So, a valid consideration, one that could have been significant if they had similar levels of emissions, but given my calculations, does not seem to be important.
Of course, this is all dependent on my calculations being correct, and my guess as to the meaning of the ‘ea/min’ on the more recent paper! Was a fun discursion, though.
Please forgive me for the length of this, @Jan_Wildeboer . If you prefer, I can pull this out to its own post and edit this to just a link.
This sounds like the paper that was released a few years ago that concluded that taking a shower meant you inhaled massive levels of magnesium particles straight into the lungs from the salts dissolved in the water. Tabloids concluded that you should use a bath instead… Turns out that although that you do receive masses more Magnesium taking a shower, it’s still negligible and we shouldn’t worry.
I still use a hepa filter and a carbon activated filter…
@Howard_C_Shaw_III
Great post, and you are right, this is an extremely complex field of study. In fact one in-which I’m ill equipt to make conclusive judgements and comparisons. So unfortunately I must rely on those who are far better equipped to help me draw my own.
I’m not saying your comparison is not valid, but for me, until I see some data from those who I know are able to make those conclusions comparing 3Dprinting and a candle burning I must hold my own judgment.
Like I said before, I’m more concerned with the VOC’s, not necessarily the UFP’s… Which will probably come back and bit me in the butt… 
Thanks again for you post, it was interesting and informative!
Thanks, and yeah, I certainly understand about wanting someone you have reason to trust weigh in.
I just got used to using these sorts of back of the envelope scale judgements as a self defense mechanism against the media’s tendency to blow anything and everything out of proportion. I listen to skeptical podcasts, and they like to point out things like the difference between relative and absolute risk increases, and how the media likes to jump on an eighty percent increase, or even an eight-fold increase to have a catchy headline, ignoring that the absolute risk started so low that the increase is on the order of less than one person in a thousand and such. Doing these kinds of sums helps me adjust my own concern level appropriately, and hopefully if nothing else, maybe I’ll have inspired some people to run these kinds of numbers themselves.
As a side note, WolframAlpha is an intensely valuable tool for the layman in this kind of thing, because it tracks the units for you, which can really help you recognize when you went the wrong way in multiplying versus dividing, or swapped a numerator and denominator, just by seeing some completely unexpected units in the answer, such as inverse mols, and for giving comparatives that can offer a sense of the scale of an answer.
@Howard_C_Shaw_III Your comments are much appreciated! If you want to, I would certainly look forward to see a post wrapping up your comments and putting stuff into (your) perspective soonish
I’m guessing nobody in these comments has ever been on the floor of an injection molding facility.
@Chris_Larsen I’ve been there, quite a few times. But injection moulding and FDM don’t have that much in common wrt emission production AFAICS.
@Jan_Wildeboer Why would it not have much in common? Both are thermoplastic processes with the same materials. It smells exactly the same to me, only orders of magnitude stronger. I’m speaking relative to VOCs, not to fine particles, many of which might be removed with the air handling on the presses.
@Chris_Larsen FDM works with filament, not granulate. Injection moulding is high pressure, lots of hydraulics, high temperature on big areas. FDM is very limited heat at the printbed and nozzle, very small hot area, no hydraulics etc. While both produce “stuff made out of polymer” that’s where the comparability ends IMHO.
3D filament is made from that same granulate. If anything, there is less VOC in filament than granulate because of the mold release agents that are required to get injection molded parts out of the mold. Those same mold release agents would have burned out of the filament when it was formed (if they were even added in the first place)
I’m saying that if the tiny amount of material and VOCs released by a 3D printer is a concern, then everyone who works 40 hours a week on an injection molding plant floor would already be dead, since their dose is literally thousands of times higher.
@Chris_Larsen Agreed. But domestic use of 3D printers is quite a different setup. There can be kids around, the printer is in the living space 24/7 etc. That’s definitely different from going to a factory for an 8 hour shift 
Went back through and built a Frink program (useful to make sure that no transcription errors occurred during multiple steps with WolframAlpha - Frink is a programming language that also tracks units like WA does, but additionally supports variables, printing, etc. Mathematica or Maple V, etc, would also serve.) and it caught an error - 1.65 mg / 15 min is 110 µg/min, not 76 - obviously, I transcribed the mg value from the wrong row in that step in WA.
That shifts the final answer to 1.2 x 10^16 per minute - which does not substantially change the results (in spite of adding another order of magnitude), or my conclusions.
Edited: Correcting my correction - it was the 1.65 that was in error in the first run; it was mistranscribed and should have been 1.12 mg. Second, I noted at the time, but forget when I was actually doing the calculations, that the organic compound figure was a fraction of the whole. Applying both changes gives 8.5050 x 10^12; still orders of magnitude higher, but drastically less so.
Added: Post is up at https://plus.google.com/+HowardCShawIII/posts/j39WQpD4yZp