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Comment by dekhn | Hacker News Reader

I don't know anything specific in this case (I have been following it since it was first reported, since it's local, and mysterious). But my first suspicion would be the CO2 gas supply to the laser. Low-quality CO2 gas has CO impurities. I think a leak in the gas supply, combined with really poor ventilation, could possibly lead to this situation, but I'm still surprised there would be enough CO to fatally poison 2 people and 2 cats.

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The CO2 laser tubes sold to hobbyists are sealed. There is no gas supply. Large industrial lasers use a gas supply in order to cut faster and at higher power.

Some home-built tubes do use a gas supply, but virtually no one builds their own CO2 tube to use in a laser cutter when better tubes are available on eBay for $100.

I never said anything about the laser tube. I think it's more likely they did use a gas supply and that leaked.

What would you use a CO2 supply for with a laser cutter or 3D printer then? I can't think of anything.

Maybe I misunderstand how CO2 lasers work. But my understanding is that a high-powered CO2 laser can be run using a gas supply from a tank/regulator. As mentioned elsewhere, this is typically only done in industrial settings, but some home laser cutting enthusiasts want more power. The tank contains some mixture of gases, primarily CO2, but containing other gases, likely some CO. If the tank/regulator to laser tube connection is leaking in a closed room, then the CO concentration in the air will increase.

This is speculation on my part based on my assumptions. If my assumptions are incorrect that's fine.

The "gas supply" you're referring to is most likely an "air-assist". Laser cutting works better when you have a flow of air (just air), blowing the smoke out of the way.

Many folks use small compressors for this purpose.

But it won't have anything to do with CO levels.

Yes, but those would feed CO2 into the laser tube, which I thought you just excluded ("I never said anything about the laser tube.").

As others have said, normal laser cutters have sealed tubes, although its of course possible they had some DIY rig for whatever reason. MIT students building their own CO2 laser just for fun doesn't seem all that odd, using it for long time in a cutter maybe more so. I don't know if a leak in a CO2 system would lead to CO poisoning or no. CO produced by the material cut seems more likely to me.

Sorry, I guess it is a bit unclear: I assumed the leak preceded the laser tube proper. When you hook a tank/regulator up to an evacuated tube, there can be leaks "before" the laser tube (I spent a month building vacuum chambers, and most of my leaks were in the connections between the vacuum pump and the chamber, not the chamber itself).

however, after thinking some more, I agree that CO from material cut is more likely.

I've never seen or heard of a non-industrial laser cutter with a gas supply.

Air assist, yes (to clear smoke and particles from the beam and protect the focus lens from soot), but that's just an air pump, not a gas supply.

CO poisoning is cumulative. It takes a long time for CO to get unstuck from hemoglobin. It could have snuck up on them slowly, then one evening with the cats "napping" they felt particularly tired and thought to themselves, "We must be in hibernation mode from the chilly weather," then they went to sleep then never woke up.

CO is odorless. You might get a headache, or you might only feel tired. What's worse: a lot of CO detectors are pretty shoddy.

Your description makes me increasingly worried; do you have any preferred CO detectors?

Avoid cheap ebay stuff. I think Consumer Reports have done a rating of those devices sometime. However, that might be out of date at this point. I just did a search on YouTube, and even those random reviews seem to date from 2014. There should be a way to verify those. Maybe Cody's Lab could handle this?

Co2 lasers are 30℅ CO by design. Kind of like a halogen cycle thing but recombinant.

There is very little gas in a tube though.

It seems the poisoning came from the operation of the laser, which means that the gases inside the laser were not involved. (It doesn't seem from breakage of the tube, but from usage.)

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