Is 3D Printing Safe? or DIY Testing for HCN from ABS and Nylon 3D Print Material

  By 3D Printing, we are referring to the majority of FDM or filament feed, BukoBot, Printrbot, Makerbot, TOM and others that use plastic line and a heater block to print parts.
   And, what exactly is "safe" anyway..?
If we eliminate the obvious, the fact that the belts and motors can pinch a finger as well as a heater block operating at 200+c will definitely burn you, we are left with the one unknown.  That is of any hazardous fumes and odors that may be emitted by heating the plastics.  We not only can't see these gasses, but most of us don't have a device at hand to make a measurement.  
  
    The intent of this DIY is to explain how to build a test apparatus to determine the safety of the material you are using to print your parts.  Of course in doing so, we were able to measure and report on various common matereials.

    If you just want an answer to the question "Is 3D Printing Safe" without reading the excruciating details, you're in luck.

"Yes" Based on our measurements using the world Safety Authorities (OSHA NIOSH ACGIH) Limits, 3D Printing is safe.
There was NO measured HCN from "3D Printing ABS" based materials at specified temperatures.
There was NO measured HCN from "3D Printing Nylon" based material at specified temperatures.
There was 0.1ppm of HCN while printing with a "Non-3D Printing" material (Trimmer Line)

Even in our worst case testing in an enclosed 12" cube at 420C (788F) for 10 min the maximum reading was 1ppm, again, trimmer line.  The OSHA safe limit is 4.7ppm.

Quick Q and A

    Did you find any items of note?

1. We found that before the threshold was reached, the plastics became "unprintable" and would halt/jam the printer.
2. There is a lot of naturally occurring HCN.  You will probably encounter more HCN at an outdoor marshmallow campfire than we measured in our testing.  Due to it's shear quantity as opposed to the small quantity we print, burning wood creates a lot of HCN.  
3. Again, our testing shows no HCN measured from 3D Printing materials at correct temperatures.

     What gas would make 3D Printing unsafe?
An excessive amount of Hydrogen Cyanide (HCN) - A gas emitted by plastics when they are set on fire or breach pyrolysis.

     And what is an excessive amount of HCN?
The international (OSHA NIOSH ACGIH) maximum allowable exposure to HCN is 4.7ppm

    So? How much HCN did you measure while actually printing?
3D Printing  ABS from various 3D  Printing material suppliers in China, the EU and US = None
3D Printing Nylon from taulman3D 3D  Printing material supplier in the US = None
Two brands of Trimmer or weed-whacker Line mfg in the US = .1ppm

     Where did you get the 3D Printing material?
Defined 3D Printing Material -
ABS1 = China - A
ABS2 = China - B
ABS3 = EU
ABS4 = US
Nylon1 = US
Nylon2 = US

Non 3D Printing Material -
Trimmer1 = US
Trimmer2 = US

      What did you use to measure the HCN?
Industrial Scientific Corporation T-82 Single Gas Monitor
Calibrated HCN Sensor
Certified calibration 1 day before testing
Certificate of calibration
Certified by UL, CSA, CE
Resolution .1ppm

    What was your absolute highest reading?
Trimmer line "A" at 220c+ = 0.6ppm -1.0ppm in a semi-sealed enclosure (12" x 12" x 24") for 10 min
This is a "cumulative test" as the gas is allowed to accumulate in the enclosure, thus it's concentration in ppm is higher.
This is NOT a printing test, but one of several tests done to answer cumulative concentration questions.

Excruciating details,

"Safe"...?

Electrical:
     Today, most 3D Printers use modular power supplies.  Either re-purposed ATX (Computer PS) or enclosed wall power units, such as used by laptop computers.  These are already UL listed and tested.  Most of these power supplies don't exceed 24 volts, including power to the Hot-End.

Mechanical:
     Again, there are obvious safety concerns with respect to motors and belts, pulleys and or threaded rods.  However, once we see these components in operation, we know to use a bit of caution and not stick our fingers in the moving parts.

Thermal:
      There are a few hot components we need to be aware of.

1. Stepper motors - These can get hot, but usually not hot enough to burn you.  Most motors have an attached fan to keep them cool so as to last longer as heat damages the motors bearing surface over time.    
2. Power supply - These are covered units, but as they dissipate heat we need to make sure they have access to ventilation, i.e. don't block the little cooling holes and replace air filters when needed.
3. Build table - These are the platform we actually print onto.  They are usually heated to a temperature that will burn you.  Almost all of these are vividly marked in some manner warning of "HOT" and "Do Not Touch".  This is an actual UL requirement if the printer is certified.
4. Hot-End or Heater block - This is the component where the plastic is melted and flows from a small opening/nozzle. This will be very hot.  Between 180C (356F) and 275C (527F).  Again, this will not just burn you, but mark you for life.  Recently, you may have noticed that some 3D Printers have started to ship with brackets, or shields around the Hot-Ends.  And in some cases, a completely enclosed printer where access is only through a door or lid.  This comes from various UL and CSA requirements for finished goods where rules to protect the consumer come in to play.  As of yet, 3D Printer kits have not been required to meet a lot of the same rules. 

Chemical/Gasses:
    While most of us have tape measures and wrenches to make mechanical measurements/adjustments, volt meters to make electrical readings and temperature sensors to measure hot parts, almost none of us have unique gas detection equipment to detect gasses emitted by printing.  And because we are changing the state (heating and melting) of plastics, they will emit  fumes and odors.
   
3D Printing Measurement History
      We can't say that no one has made this specific measurement prior to now, just that we were not able to find any information on-line or through contacts.

Step 1: Safety

Safety:
                      First, research the history of similar conditions or testing.
     Research was extremely easy. A simple Google search on HCN measurement techniques along with some outreach to injection molding companies proved that this has indeed been tested and certified safe in much larger quantities. 
      3D Printing is really just die-less injection molding.  The plastic is heated and forced to go where we desire.  It cools and we have a part.  So, the injection molding specialist are a good place to start.  Contacting a major injection molding company in the eastern US, we were able to get the Industry Standard on injection molding safety and hard measurement of HCN with Nylon specifically.  For Nylon, the industry goes by what is known as "The Barns report".  This is a full up actual real time HCN testing of a injection molding machine running at 270C with 100's of pounds of material.  The resulting HCN measurement was less than 1ppm, so we assumed with a tiny amount of Nylon, we were pretty safe.  However, we were also going to do some "cumulative testing" where we all but seal up a specimen and heat it to extremes of 400C. More on that later.

Safety Setup:
    So we're about to build a tester to test for hazardous gasses.  And in doing so, we will intentionally create a worse case 3D Printer condition to force the generation of these gasses.   What precautions should we take?

1. No Bystanders - This is not something you do while a bunch of folks are in the next room eating lunch.  Alert everyone in the building you're going to generate hazardous gasses.
2. Dead Man switch - Well, not really, but you need to be able to turn heater temperature "OFF" outside of the danger area. 
3. Remote Visual - If while performing the test, you reach the OSHA Limit, you are to immediately leave the room to seek clean air.  To understand if you can return, you can use a WIFI connected video camera pointed at the sensor.
4. Ability to vent the room remotely. - If extremes happen, and someone does not get to leave from collapse or they have been overcome, you must be able to quickly vent the room to allow safety personnel access.
5. Clean up - At low temperatures(78F) , HCN gas can liquefy on surfaces.   After each test, you must wash off/spray off any surfaces that will be used for the next test as HCN can linger.  In addition, you must wear typical nitrile gloves to keep from absorbing HCN through contact that has accumulated on cool surfaces.
6. Have a smoke detector as you never know.

    For our testing:

1. Location was a garage with no other inhabitants.
2. The Heater cartridge was on an extension cord that looped 100' from the garage.
3. We had a WIFI enabled video camera on the test setup including the HCN sensor.
4. We had a 130 cfm vent in the top of the garage and the power garage door remote.
5. We used a power sprayer for clean up and just sprayed water.  No other chemicals.
6. We had a smoke detector and fire extinguisher.

Additional detection method:
      If for whatever reason you suspect that your sensor may not be calibrated or working correctly, there are two additional early warning alarms you can use.

1. Bugs, yep bugs.  HCN is considered a great bug killer as bug's will literally drop out of flight if they encounter anything above about 1.8ppm of HCN. 
    
2. The odor of almonds.  This is in the literature and sounded a bit odd, but we are now believers as we got a whiff while testing trimmer line at elevated temperatures.  We were reading spikes at about 0.6 - 1.0ppm when we detected this odor.

Disclaimer:
This testing may be performed by experienced, skilled users, at their own risk. to the fullest extent permissible by the applicable law.  taulman and taulman3D hereby disclaim any and all responsibility, risk, liability and damages arising out of death or personal injury resulting from any testing defined or described.
NOTICE:  HCN is considered lethal at >30ppm

Disclosure:
This testing was performed by the taulman3D group.  taulman3D.com is now a vendor of new Nylon based 3D Printing materials. 

Comments

[chimera15]

Really interesting...so it won't kill you outright...but does that mean that it wont give you cancer in 5 years if you're in your bedroom printing with abs 24 hours a day? I know I can barely stand the smell after a few hours and feel like I'm already growing a tumor...so it can't be completely harmless. I'd like to see a study of all the vapor that abs/pla/line gives off..and what exactly the hardness is of each of them, and if there's a difference between american and chinese abs for instance in the qualities. This is really an interesting subject.

[sunaj58]

Hey,chimera15, sounds like a great "ible for someone who wants all those answers, to actually do. Seriously.

[samurai1200]

Invaluable information in this not-so-'ible 'ible!!! Thank you for going through the steps.

HOWEVER, I do have a question: What is causing me to get a headache when I print ABS after ~20 minutes? I mean, the HCN levels might be of an OSHA-approved level, but I wouldn't be getting a headache if my body was OK with the altered environment.... My room is roughly 20x20x20 feet and i am generally at the opposite corner of the room when i am printing (so my guess is i'm exposed to the lowest PPMs over there).

[taulman]

1200, It's of course difficult to say, however, there are actions you can take to make a determination as to further actions/resolutions:
1. If you're not currently vented, then add a simple vent as shown in the two renderings in the ible. A sufficient vent is made up of a standard 100cfm fan (as in most desktop comp) an inverted storage box and some 6" dryer hose to an exit.
2. Most overlook the fact that some stepper drivers emit a lot of noise just above the audio spectrum that can still have an affect. Try running a few prints with no heater and no material letting the stepper go thru their routine.
3. The material its self. There are suppliers that sell "odd" colors. Our China contact told us that these "odd" colors may be injection house purges and reject remelts. Reputable dealers will only sell virgin material.
4. Styrene can be a source of your issue as it does not dissipate easily. You may want to run the same test as noted in the ible and measure for styrene or "combustible gasses". If so, do a search on materials that emit almost no odor by others in their blog, IRC and wiki comments.
5. Long term exposure to levels higher than 1-2ppm of HCN have shown to cause similar symptoms but again, we saw no low level (0.1ppm) readings within proper operating temperatures excluding trimmer line.
6. Check out the following link for additional low level emissions that you may be sensitive or allergic to.
fire.nist.gov/bfrlpubs/fire86/PDF/f86017.pdf
And again, as we say in all of our ible's, one should "vent all fumes and odors"

[samurai1200]

ah, some awesome points to consider. but yeah, it seems the only real way to make sure youre not harming your noggin is to vent to the outside world...

[Michael_oz]

...and make it someone else's problem?

Perhaps the 3D community (that includes me) needs to think this through a bit harder.

[samurai1200]

So, then, what do you suggest? Charcoal filters on an active exhaust?

[Michael_oz]

That's what I'm looking at, but 'science' must have looked at this already. I'll be looking around some more.
ps I wasn't having a go at you, my interim solution is an open door/windows to the outside...

[samurai1200]

Well here's what I'm thinking -- I agree with you that "science" must have looked at this already, and therefore determined no need to change the status quo, i.e. venting directly into the environment.

I remember reading a paper that said heating filament to the levels needed for FFF yields insignificantly low outgassing from both PLA and ABS. It'll take some digging to find the paper, I didn't bookmark it.

I would imagine that this would change once FFF printing becomes ubiquitous (= higher volume of by-product gas in the atmosphere.

[evileddead]

Just so you know in the future, Cyanide has that tell-tale almond scent and taste, as do most compounds it's a part of.

[pmowers]

@evilddead- about 1/3 of the population cannot smell cyanide, and of those who can, it deadens the nose to it in short order.

[taulman]

pmowers, you are absolutely correct as this 1/3 note was part of every techncal paper we were able to aquire in our research. There were a few technical documents that implied that this had been tested for, as part of larger tests however, these may be paywalled studies. Thanks for your clarification.

[pmowers]

My background is laboratory medicine and we used a cyanide compound to measure hemoglobin in blood. There were a fair number of students and techs who could not smell it, while I could tell it across the room. One of the reasons that HCN was used as a chemical weapon (blood agent) was because it would numb out the olfactory nerves, while at the same time stimulating the respiratory centers of the brain. This is the reason that states use it in the gas chamber, you cannot hold your breath, one whiff and you have to breath more.

[taulman]

Thanks
You are correct as this is also noted in the able in section 2 as an alternative detection method.

[BobCat]

Excellent work. Instructables needs more careful, rational, and scientific work like this. A *lot* more. :)

[taulman]

BobCat, again thanks for your comments!
As mentioned in the ible, there were other materials tested along with 3D Print ABS and 3D Print Nylon. The 2BEIGH3 has hot ends capable of temperatures that will accomodate Tin and Bismuth metals. As new 3D Printing materials come on-line, it's our hope that others jump in on test procedures and methods.
Today, you can run polymer and co-polymer combinations and calculations and litterally have the combination extruded for you at any one of several houses. We beleive that this is an excellent move forward in 3D Printing and look to others to add their ibles on test and procedures.

[taulman]

BobCat, thanks for your comment!

[KahlZun]

wait.. you can use weed-whacker plastic in a 3d printer??

sweet!

[galaxyman7]

Ya, go to the reprap page here:
http://reprap.org/wiki/Polyamide#Instructions

[makermike]

This is a nice Instructable with better than usual rigor in its testing. However, speaking as a chemist, I also wonder about what other things are outgassing from the hot plastic. HCN and CO are certainly to be worried about, especially since CO is odorless, but as other commentors have noted, there is a smell associated with 3D printing. If you're smelling something, then something is volatilizing from the hot plastic. What?--probably a mixture of a bunch of things, a complete characterization of which is likely beyond DIY science, although I'd be surprised if someone hasn't written up a paper on it already.

So common sense would seen to dictate some level of precaution. Venting your work space would be nice, and don't sleep next to a working printer. Is it any worse than breathing in solder flux fumes or sawdust? I don't know.

[taulman]

Makermike, First, thanks for your comment. We agree, in that venting is always the best approch. We do not want to get into a vendor to vendor comparison as those that wish to can use this ible for that. However, with a little research, we did find comments on blogs from those that had found ABS materials that gave off almost no odors. We did not test that specific material but again as you note, some sort of comparison testing would seem like a worthwhile effort for someone in the 3D Printing community.
As a technical note, in that the process from solid to melted back to a solid takes place in a volume the size of the eraser on the end of any pencil, it seems that a simple well placed miniture vacume hose/line would all but eliminate most fumes and odors.

[mgalyean]

Very well organized. I like the "how to do science" instructables in general, but this is really good. Excellent breadth and depth covering the method, materials, regulatory levels, hazards, etc.

[taulman]

magalyean, thanks for your kind comments. It does mean a lot to us as you can see that there is considerable time, effort and equipment involved. But of course, well worth it to the community!

[mgalyean]

No really, while I truly am excited about the "maker" culture exploding around us, being a nerd/tinkerer myself, there is so much disrespect for what has come before in many cases, and most disturbingly sometimes a seeming disrespect for rational thought itself at times (my young stepson still swears he could build an over unity generator out of permanent magnets; he has it "all in his head, just needs to work out a few niggles"). I just smile and tell him to build a prototype that works and I'd be overjoyed to admit that I, and Isaac Newton, and the entire edifice of human science to date really, is full of crap. It is simply refreshing to see a 'structable like yours that instructs in solid methods of rational thought after watching my son spend hours on the internet ooh'ing and ah'ing over the youtube videos that "prove" he could build one. He just doesn't get that he is getting intellectually punked by either smart-assed pranksters, or by self-convinced nutcases. Hey, I'm glad he is curious. I just want him to be smart-curious, not gullible-curious! :^D

[taulman]

mgalyean, as a side note, you should have seen the look on our taulman3D physicist face when I told him we were going to generate hazardous gasses and watch as we took videos of the process in real-time. There was this long pause and he just said "intentionally?" He then gave us all a quick course on safety!

[taulman]

Yes, I learned the lessons early on, as a young wild-eyed engineer, I was lucky enough to bump into a much older engineer who after gracefully listening to my ramblings of “new stuff” commented the following:
An inventor’s dream is the relentless elimination of technical roadblocks and the only successful inventors are the ones that see the “law’s of physics” as a guide, rather than a roadblock!
I'm always pleased to see kids actually "doing" rather than watching.

[iortolan]

Nice article, thanks.

[taulman]

Thanks for your comment!

[fazgard]

Thanks for the great write up and discussion on all of what I would call 'nagging FaQ's' that sit in the back of the mind ..

Well done.

[taulman]

fazgard, thanks for the comment! Again, it is our hope that others can use the ible to test new and inventive materials for 3D Printing as it's relativity easy to have extrusion houses mix new polymers.

[BeforeTron]

REALLY REMARKABLE! I had a nagging concern about my 3D printer offgassing some type of "bad-ness".
I print PLA, and I have been told it is completely safe. If ABS is this safe, then I can only (emotionally) feel good about printing PLA. (of course I would have to test to make sure!)
This was so comprehensive and such an incredible public service announcement.
thank you so very much!!!!

[taulman]

First, thank you for your kind comments.
We've only heard good things about PLA. Some quick research would define what gasses to look for if any and what the proper equipment would be to test.
Again, thanks for the comment!

[SenKat]

Most impressive ! I do not own a 3d printer (sigh !) but the info you put out there is GREAT for those that do - don't let "Mr. Ocean" get under your skin - trolls of all types exist to simply create misery wherever they roam ! Keep up the great work - this is the most detailed and intelligent 'ible I think I have ever seen.

[taulman]

SenKat, thanks for your comments. I think sometimes when we don't know the answer, and after doing research we find to large a swing in probable results, we are to often left with false impressions. As this is important to us all, we believed it was a worthwhile exercise to nail it down for everyone.

[SenKat]

Worthwhile is honestly an understatement - you went over the top - thanks for the great info !

[SenKat]

P.S. Faved, followed, and 5 starred !

[txdawood]

Thank you for this information-full instructable! Good job!

[taulman]

txdawood, Thanks for your comments.

[eecharlie]

Is HCN the only dangerous off-gas that can be produced by heating ABS and Nylon in the temperature range used by 3D printing?

[taulman]

charlie, HCN and Carbon monoxide were tested due to their toxicity.
For a full list of gasses, download the linked Barnes report for Nylon and the following link for ABS.
fire.nist.gov/bfrlpubs/fire86/PDF/f86017.pdf
Again, most gas emissions begin at much higher temperatures than we use for 3D Printing.
However, as we say in all of our able's, one should "vent all fumes and odors"