Comment by Animats | Hacker News Reader

Comment by Animats | Hacker News Reader

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"3D laser printer" probably means a Glowforge. Nobody else calls them that. Their documentation says "Lasers normally require some ventilation via a small tube out a nearby window. Our optional Air Filter that sits under Glowforge and ventilates using HEPA filters and charcoal, meaning no outside ventilation is required." That won't do much if you cut something that emits carbon monoxide when heated. That includes some common plastics, styrene being one.

There are lots of things you don't want to cut on a laser cutter unless you're cutting under an inert gas, or at least nitrogen. Polycarbonate, any of the chlorinated plastics (PVC, some synthetic leather), styrenes, and polyethylene, for example. ABS melts, and Fiberglas's glass component won't cut. Acrylics cut very well. Delrin cuts OK. Wood and cloth are OK. Techshop is careful to teach people about this.

TechShop's laser cutters have compressed air coming in, a big exhaust hose going out, and a fire extinguisher nearby. TechShop has an ad slogan, "Don't try this at home. Do it at TechShop". There's something to be said for that when you're using industrial-strength tools.

In addition to the two people, their two cats died. Operating these things in a closed room is a really bad idea.

I'm the CEO and cofounder of Glowforge - we're so saddened by this tragedy. Our product was not involved, but that doesn't make us feel any better about this loss.

If you use a laser, ours or anyone else's, please go back right now and re-read the safety instructions. Accidents like this should never happen. My heart breaks for those affected by this.

OK, it's good to know it wasn't yours. Thanks.

It would be appropriate to put a CO detector in your units before somebody does that with one of yours. That definitely needs to be in the "filtered" units that are supposed to operate with no ventilation.

Might be worth editing your original comment to remove the suggestion that it's a Glowforge, just to avoid unnecessarily associating a specific company that wasn't involved in this tragedy.

Are there CO detectors to buy to react before it's too late ?

Many smoke alarms also measure CO now.

Even if there were smokealarms with CO dedection it's really bad practice. Carbon monoxide dedectors need to be installed on to walls 100-150cm from the floor. In the bedroom I would recommend the height of bed. The reason for all that is the fact that CO molar mass is really similar to air molar mass AKA "that shit will reach the sealing when you're long dead".

Sorry, but what are you talking about?

Yes, CO is similar to air's molar mass (it's actually slightly lower), meaning it will diffuse evenly through the vertical space in the room. The concentrations at the ceiling will be the same as the concentrations on the floor.

Stop spreading misinformation.

But if sources are at human head level, by the time it reaches the ceiling, you already inhaled a fair amount of CO ? what did I get wrong ?

Nope.

Diffusion of gasses in the air is an extremely rapid process. In a minute the concentration would be the same throughout the room.

I found this paper that directly tested different positions of detectors:

"Should the placement of carbon monoxide (CO) detectors be influenced by CO's weight relative to air?"

http://neilhampson.com/uploads/3/4/0/6/3406995/2011co_weight....

Their conclusion agrees with you completely:

What does this say about the placement of residential CO monitors? It would be reasonable to place them anywhere in the room and expect them to be effective. Every scenario imaginable in a home would only speed the mixing of the gas within a real room, as compared to a sealed chamber — people walking, forced air flowing from vents, CO entrainment with warm air being released into a room at floor level and then rising.

The belief held by many that CO sinks is clearly wrong. Statements such as ‘‘Carbon monoxide is heavier than air, and will pool in lower areas’’ need to be refuted with facts (5). Even if CO were significantly heavier or lighter than air, it would still distribute equally from ceiling to floor.

On the other hand, they did find that the rate of diffusion can be much slower than "in a minute":

The time required for the equilibration of CO concentration was different depending on the level of infusion. It occurred most rapidly when CO was introduced in the middle of the chamber (2 min), at an intermediate rate when introduced at the bottom (40 min), and most slowly when introduced at the top (105 min). Nonetheless, the ultimate concentration was equal throughout the chamber, with no suggestion of any pooling on the floor, layering in the middle, or floating on top.

Aight

The air filter costs an additional $750 extra when you buy the $3000 Glowforge, I could see students skimping on that and no realizing the implications. https://glowforge.com/order

That said I watched the video for this product and I'm really looking forward to when these are widespread. It's a very exciting industry. I'd definitely buy one of these when it gets to around $1k.

> I could see students skimping on that and no realizing the implications

They weren't students. Roger was a game developer while Valerie was a post-doc. They just happened to live in Berkeley.

Why are we talking about the air filter? a) whether it was a glowforge system is still speculation b) air filters do not have anything to do with CO, only particulate.

The order page definitely doesn't have any warning about the basic - even I would go 'Nah, what's the $720 for? Upsell?'

How about:

Glowforge Pro + Air Filter: $5,995.00

Glowforge Basic + Air Filter: $3,745.00

Glowforge Basic: $2,995.00 Warning: You may die when using Glowforge inside without Air filter (link). You may also die when cuting these materials (link) inside even with air filter.

And all come with 2 co detectors, internal and external

Selling the product without that filter could be considered immoral.

Yeah, in my lab we prohibited cutting anything with chlorine, including PVC and polycarbonate.

The results are really bad anyways, it melts and burns. I'm curious though, can you get good cutting of polycarbonate using an inert gas shield? That would be interesting.

CNC zone reports that cutting polycarbonate on higher power lasers under nitrogen can be made to work, but it's touchy.[1] The plastic tends to melt rather than cut. Pre-freezing the material is suggested.

[1] http://www.cnczone.com/forums/general-laser-engraving-cuttin...

Polycarbonate has no chlorine.

Their laser printer was stored/run in their closet. They may have been doing this for a while with no problems because Berkeley is so nice and everyone leaves their windows open.

Berkeley has been unusually cold/rainy this last week and I'm guessing they sealed up their apt and didn't realize how dangerous that was.

I wonder if a catalyst converter would help.

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