I’m going to go out on a limb and say it wasn’t a 3D printer that did the deed, certainly not the type shown in photos within the article; those are FDM printers (Filament Deposition Modeling) that work on the principle of extruding molten plastic out of a nozzle to lay down the material of the print, there’s no burning involved and if there is it’s because something went very wrong and the thing won’t be printing anything, for example if extruder temperatures are too high the filament will decompose in the print chamber, not burn since there wouldn’t be enough oxygen in there for that to happen. The only way an FMD printer would produce any significant amount CO is if it’s on fire.
The article mentions a laser 3D printer and my hunch was that they actually meant a laser cutter, since the only type laser 3D printer that can be expected to be used at home would be a DLP machine, which uses a UV laser to cure resin inside a vat layer by layer, again, no CO is produced.
Sure enough, I checked and found this discussion thread, there was one 3D printer and one laser cutter in the room, also the theory of CO poisoning from the laser cutter is just speculation.
I guess we can chalk this up to the media erring on the side of hype when a buzzy trendy word can be appended to a story, such as 3D printing.
Having said that, there are health considerations for FDM printers, some materials can release not-so-nice fumes and all of them, to one degree or another, generate airborne particulates that can affect people. Irun my printers in a spare bedroom for that reason.
3D printers are a happening scene today.