Sustainable air purification is one of the most interesting problems to solve for long term space exploration. It took us a few decades to realize that work in

Sustainable air purification is one of the most interesting problems to solve for long term space exploration. It took us a few decades to realize that work in popcorn factories can cause severe lung disease, so there's probably still a lot we don't know about what environments are safe and how much purification would be required on a strange planet, even after we get the right balance of nitrogen and oxygen down.