A smart student youtuber did some excellent discovery work and analysis using her Bambu printer and Bambu PA6 CF filament and found prima facie evidence that, to one degree or another, CF may become airborne while printing:
It’s more the first word on the topic than the last word, but definitely food for thought! The obvious question is “How hazardous is it?”, but she mainly was data gathering and didn’t attempt to reach any concrete conclusions as to threat level.
So what is the purpose or danger involved with airbone carbon fibers. Don’t think its so much of a health risk. We are composed mainly of carbon, so why would it be dangerous if it got inside us.
No idea. Maybe it’s an irritant because of the spikiness that your lungs have difficulty rejecting? Why is airborne asbestos bad to breathe? Isn’t it inert? I’m not saying it’s the same, but it would be at least the basis for a concern if you were looking for a possible comparable to fuel a theory that there might be a hazard. Or blacklung. Or brownlung. Or whatever. But I’m not saying there is. I haven’t looked into it at all, but maybe it’s worth some questions to grok. I’m not here to convince anyone there’s a hazard, as that would be a huge burden of proof. It’s called decision making under uncertainty.
Oh ok, but also i do not use carbon fiber filament of any type, I have only used PLA until now, which is biodegradable and made from corn starch mainly.
You probably get more carbon in your lungs driving to the store for groceries. More so if you live in a rural area where diesel trucks and tractors are common. (like me) 
Dose and duration.
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Silica dust might be a better comparable. It’s sharp.
Anyhow, I asked Grok 4. Here’s the prompt, and it’s answer:
My prompt to Grok 4: “How much or how little of a health hazard might inhaling air with bits of chopped carbon fiber in it?”
Grok 4’s answer:
Inhaling air with bits of chopped carbon fiber can pose a moderate to significant health hazard, depending on the concentration, exposure duration, size of the particles, and individual health factors. As of 12:07 PM CDT on Friday, August 08, 2025, the risk is informed by scientific studies, occupational health data, and anecdotal evidence, though regulatory limits remain underdeveloped due to limited long-term toxicological data. Below is a detailed assessment based on available information.
Health Hazard Assessment
Particle Size and Respirability: Carbon fiber fragments, especially those split along the fiber axis during machining (e.g., <5 µm diameter, >5 µm length per WHO criteria), are respirable and can penetrate deep into the lungs (alveoli). Larger particles (>10 µm) are typically trapped in the upper airways.
Short-Term Exposure (Low Concentration, Single Incident):
Hazard Level: Low to moderate.
Effects: Inhaling small amounts (e.g., from a brief sanding session with a mask) may cause temporary irritation of the nose, throat, or lungs, similar to glass fiber dust, with symptoms like coughing or itching. A 2023 Reddit thread reported no serious issues from a one-time exposure with a mask.
Risk: Minimal if exposure is brief (<1 hour) and below 50,000 WHO-fibers/m³ (German TRGS 905 limit).
Long-Term or Repeated Exposure (Higher Concentration):
Hazard Level: Moderate to significant.
Effects: Chronic inhalation of respirable fibers may lead to lung inflammation, fibrosis (e.g., pneumoconiosis), or increased cancer risk (e.g., mesothelioma) due to biopersistence, as noted in studies on pitch-based carbon fibers. Concentrations of 830,000 WHO-fibers/m³ near machining sources were observed, far exceeding safe limits.
Risk: High if unprotected and frequent (e.g., daily for years), with a 0.0023% lifetime lung cancer risk increase per Reddit’s composite worker estimate.
Individual Factors: Pre-existing lung conditions (e.g., asthma) or sensitivity may amplify irritation.
Quantitative Risk Context
Occupational Exposure Limit (OEL): No specific OEL exists for carbon fiber, but the German TRGS 905 sets 50,000 WHO-fibers/m³ as a carcinogen threshold. Workplace measurements of 33,000-830,000 fibers/m³ indicate significant risk without protection.
Comparison: Asbestos (a known carcinogen) has similar fiber dimensions, but carbon fiber’s toxicity is less studied—some rat studies show transient inflammation, not chronic harm.
Mitigation and Safety
Low Exposure: Use a N95 or FFP-3 mask, ventilate the area, and limit exposure to <1 hour to keep risk minimal.
High Exposure: Install a HEPA vacuum system and wear a respirator (e.g., P100) for prolonged work, reducing fiber levels below 50,000/m³.
Conclusion
Inhaling chopped carbon fiber bits poses a low to moderate hazard for short, occasional exposure with protection, but a moderate to significant hazard for repeated, unprotected inhalation, with potential long-term lung or cancer risks. Keep exposure brief, use respiratory protection, and monitor for symptoms. Let me know your exposure scenario for tailored advice!
My conclusion: impossible to judge, vis a vis 3D printing CF filament, because we don’t have a handle on the number of fibers/m^3 that might arise from such printing activity. The youtuber was catching fibers in filter paper, and I’m not sure to what degree smaller particles would even be visible.
FWIW… This one examines both glass and carbon fiber filaments:
…This one focused on whether the stuff gets stuck in your skin (answer: yes, yes, so much yes). Now, I’m not actually concerned about that, because our skin sheds continuously, so that fiber will be gone soon enough. The stuff that gets into our lungs, on the other hand? That worries me. And that is why I’ve been holding off on playing with some PA6-CF I bought until I get a recirculating HEPA+activated carbon filter set up in my printer.
So, on one hand, you’re not wrong. On the other hand, most of us don’t go out of our way to suck down diesel exhaust right from the tailpipe, but sitting next to a 3D printer doing its thing without significant filtration is pretty common. I’ve got a PETG job running next to me right now.
Speaking of which… I leave a cheap air quality monitor on the printer at the glass vent, and coincidentally it just started beeping for attention as I was typing this post. VOCs are getting pretty high. Maybe it is time for me to bump the Bento Box up to the top of the project list…
I limit my exposure by printing unattended in my big garage, where there’s lots of air to dilute whatever is coming out of the printer. Eventually I’d like to vent to daylight, if I ever get around to it. Until then, half measures will have to make do.
PLA, including Bambu Lab PLA Basic, is made from renewable resources like corn starch and is technically biodegradable — but only under industrial composting conditions with high heat and humidity. In a home compost, in nature, or in the ocean, it can remain intact for decades. It’s best to see PLA as a more sustainable alternative to petroleum-based plastics, but not as something that will simply disappear in the environment.
Many people have problems with NBR reviews and his sensationalist behavior. In fact I think this one used to be headlined as “3D printed Asbestos”.
Thanks, I didn’t know this!
Then for sure, you’ve driven an open-station tractor. 
Whether or not you believe it’s a problem, in part 2, she offers a solution and shows how to do it within the Bambulab slicer:
I like this youtuber! She’s at a far higher caliber than most youtubers who opine on this topic with lots of opinion and little else.
So clearly we all need dual-nozzle printers now! 
Great video, thank you for posting it.
I work in a laboratory and one of my colegue’s worked decades in a famous home appliances group who use plastics since the advent of plastics and since she’s my guru on materials I asked her about cf materials and about the dangers in chipping away fibers while manipulating it and melting / extruding it and she looked me with a pathernalistic face but she did not laughed at me.
So in the end this is like don’t sniff the microwaved popcorn as soon they’re done
It will be a very cold day when I take anything Nathan says as realistic. If you watch Nathans vid, it’s like a dumb downed Cliff Notes version of strelkomania’s vid.
His integrity aside, he shows something on his hand, yet there’s no proof or evidence those are in fact carbon fibers. It stands to reason but stands to reason isn’t basis for a scientific review.
He goes on in one vid to look up MSDS and chemical properties of the filaments. While he admits he’s not getting data from the manufacturer (begrudgingly admitting BL has more info) that includes formulation. Then he goes on to look up ingredients to show that they have issues warning against this and that.
(we need transparency) Again he’s supposing what the “soot” on your nozzle is dangerous without knowing exactly what that soot is composed of. He then goes on to the usual precautions one should take for avoiding fumes etc. All of that has been repeated over and over by every YouTube wanna be star.
I am not saying there is no danger from airborne particles. I am saying that Nathan should look at how he’s stating his information and try to apply some of the basics of testing (knowing your material better BEFORE testing and making conclusions) In the real world the material you collect particles on would not be a human hand. It also would use tools to examine what that particle is. What ppm is the breakdown of filament vs normal pollutants? His collection and supposition without data cancels out nearly all he has to say. I’d suggest finding a better outlet for information on 3D printing.
The woman’s analysis is far better. She addresses in depth her findings and how they may be skewed or flawed based on the collection method of data and is actively seeking to improve that to further nail down conclusions.
I still believe that this is alarmist at best, mildly dangerous at worse.
My 2 cents.
Would be interesting to test the exhaust air for carbon from the pellets also
Will probably just cause respiratory issues
Thanks for sharing this video it’s a really important point. Carbon fiber–reinforced filaments should be taken seriously, because it’s not just about smells or VOCs. We’re also talking about microfibers and solid particles that can stay suspended in the air without us noticing. Once inhaled, these fibers don’t break down easily and can remain trapped in the lungs, so the real risk comes from repeated exposure in poorly ventilated spaces.
Bambu printers already have an activated carbon filter inside the print chamber, which is great for reducing odors and volatile organic compounds, but carbon alone won’t block solid particles. To capture fibers and dust, you’d need a HEPA filter as well, so the ideal setup is to combine both technologies or connect the enclosure to an external exhaust system.
Always print with the case closed. When opening the enclosure, it’s best to wear an FFP2 or FFP3 mask, especially if you’re going to handle the freshly printed part. For post-processing, like cutting or sanding, gloves, eye protection, and if possible HEPA-filtered extraction are a good idea. Avoid using compressed air in enclosed spaces. Letting the chamber cool and the air settle before opening is also a smart habit.
I don’t think anyone needs to give up CF filaments, but they should be treated with the same caution as industrial materials. With a bit of care and good practices, we can print safely and protect ourselves and those around us.
Particles of any insoluble materials in your lungs is bad news. Fibers can be even worse, because they’re harder for the body to expel. You’re not literally made of elemental carbon, nor can your lungs dissolve and metabolize it into organic compounds. You are mostly made of water, but you wouldn’t want your lungs filled with that either; everything has its place.