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Comment by dutchbrit | Hacker News Reader

Isn't this just common sense?

It's "common sense" if you're familiar enough with chemistry and biology to realize that melting plastic means some small fraction of it will 'burn' and end up in the air.

On the other hand, many entry-level 3D printers are marketed at... children, effectively. They can make for amazing christmas presents, but there's no guarantee that either parents nor child has any idea how things work at that level. There's been a concerted effort to make such knowledge unnecessary.

All of that being said, PLA fumes are about as safe as it gets. To the best of my understanding it's about on the level of cooking food. For hours, granted, and usually without a fume hood -- but I don't think it's likely to cause health issues.

...

And so long as you stick to PLA or PETG, that's probably fine. Oh, and so long as your printer was built with a quality, all metal heat break, so you never get teflon fumes from scorched PTFE lining. And so long as there's never a thermal runaway that causes fire, and/or it was built with good thermal runaway protection.

These printers are still essentially industrial machinery, no matter how user friendly, and a lack of understanding their failure modes can be really bad.

> It's "common sense" if you're familiar enough with chemistry and biology to realize that melting plastic means some small fraction of it will 'burn' and end up in the air.

Last time I was near one, I could clearly smell the unpleasant burning plastic.

I know that smell, and rather annoyingly newer PLA's have somehow eliminated it. Which personally I dont see as a good thing. You used to know when someone was printing with PLA as it emitted a smell that was a mixture of a sweet popcorn and burning toast. These days they have little to no odour but I suspect its still putting out the exact same (if not worse) fumes.

Ah, that's unfortunate.

Some printers also come with full enclosures and HEPA filters, which do well at removing the smell -- and no doubt some of the larger fragments -- but do not actually remove the VOCs.

A good, recirculating activated carbon filter can do that. But then you need to swap it once per week (whether or not you've been printing), and you need the right type of carbon.

The general consensus between actual users seemed to be that the fumes were obviously toxic and you should avoid breathing them in. However, there were always people who denied this, and I've never seen a manufacturer warn users about the fumes.

At least PLA fumes are far less toxic than ABS. So there's that. Which is nice.

PTFE fumes though...

The results of this study actually presents that PLA fumes are more toxic than ABS fumes.

In practice though, the study shows PLA is safer because of significantly less fume creation with the lower printing temperature.

So relative risk for PLA is significantly lower than ABS, but it is incorrect to state that PLA is less toxic.

You can smell the ABS fumes so they must be worse for you. The nose knows! /s

The human nose is an extremely sensitive chemical detector, and should not be dismissed. It's effective down to a fraction of parts per trillion for certain chemicals.

https://en.wikipedia.org/wiki/Odor_detection_threshold#Odor_...

But for others, like carbon monoxide, it is useless and leaves you to die.

You can't count on your nose to warn you, but when your nose does warn you it pays to heed that warning. If your nose is screaming at you to GTFO, listen to it.

You listen to your other senses, right? When you touch something hot, you listen to your sense of touch telling you that you're about to get burned. That doesn't mean your sense of touch can warn you of all hazards, but you certainly shouldn't ignore it when it does.

That's my usual line when people talk about smell being indicative of how safe something is.

Farts smell. Carbon monoxide doesn't.

"common sense" things need to be empirically tested and validated

Honestly, not really. Even with a "super nerd" community like Voron, the popular opinion is to print ABS for functional parts but none of the standard designs include air filtering and the advice is to "just ventilate". I've noticed over the past months that questions about the "Nevermore" filter have increased but it's certainly not a widely shared best practice yet.

It is, but you still regularly see people showing off their latest 3d printer which is sitting in a kids bedroom running all day, or their office.

Often when questioned, the existance of it being in a case or there being a cheap air purifier in the corner of the room is cited as the reason why its 'fine'.

I do feel like we dont really have sense of effects of particulate matter on the body. How does the risk of this compare to walking down a street with lots or running ICE cars? Or when you go into a basement and can smell the natural gas burning - is that a similar risk?

If you told me being in the same room as a PLA printer was 10x worse I would believe it. If you told me being next to a car for 5 seconds was 10x worse I'd believe it. As far as I've read we dont have great metrics.

In "ICE cars" the biggest sources of particulate matter are the tires and brakes¹, don't electric car have those too ?

1) https://www.researchgate.net/publication/317425487/figure/fi...

Good point! I was mistaken.

Though I think larger point stands that its very hard to know risks of different particulate sources (like brakes).

Tires yes, but since EVs use regenerative braking at least some of the time I would think they'd be slightly better in that regard. Regenerative braking does not engage the brake pads.

We really do not have a sense of these things. We are often overconfident in our limited senses. I was being poisoned by carbon monoxide from my oven and did not realize it until it was too late. I told myself "it cannot happen to me". Thank God for a few related HN comments, and a hunch to buy a CO meter.

Common sense is the least common of the senses.

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