This answer to the question in 3D Printing SE How is 3D printing done in space? says
The first big space-specific issue is actually air quality. You can't just open a window to air out the molten-ABS smell from the ISS!
FFF printers put out fumes and nanoparticles. In a space station, the same air gets recycled over and over, and the air purification systems have a specific set of contaminants that they are optimized for, as well as a design capacity for air turnover and chemical removal rates that won't be adjusted just because somebody's printing a space-ratchet today. Protecting cabin air quality is a huge design factor for any experiment that goes into space.
The Made in Space printing experiments on the ISS to date were performed in one of the vacuum experiment chambers, so any unfiltered fumes (or fire flare-ups) could be vented directly to space if required. In the long run, this isn't going to work -- other experiments may need the vacuum chamber, or "production" printers may be too large to fit. So the printer needs to have its own internal air purification system.
Question: I am wondering what kinds of activities, experiment and, procedures done on the ISS must be done in vacuum or atmospheric isolation cambers that can be vented directly into space? Exclude anything that actually requires vacuum or a specialized gas environment.
hint: apparently 3D printing is one.
