Living is a smelly endeavor. Here on Earth, humans have developed a range of modern approaches to keeping clean and fresh-smelling. In addition, cooking strong-smelling food is manageable with the simple cracking of a window or two. But in space, it is not that simple.

Recently, NASA engineer Robert Frost and retired astronaut Clayton C. Anderson offered some insight with their answers to the question, “How does NASA manage odor inside [the] International Space Station (ISS)?” on Quora. Some of what they had to say may be surprising.

The International Space Station houses six human beings at any given time, and those inhabitants are stuck inside and with one another. Fortunately, the interior environment is tightly controlled, but odors from human bodies and activities still pose challenges. According to Frost, a micropurification unit in the service module removes high- and low-molecular weight air contaminants. A “Trace Contaminant Control Subassembly” performs this role in the laboratory environment. Both systems require regular service in order for them to function optimally.

“Either one is capable of providing the trace contaminant removal for the entire ISS,” said Frost, implying that there is redundancy in the capacities of the two air purifying systems.

While Frost knows the technical details of the air purification systems, Anderson knows the practical applications. As an astronaut, Anderson spend 167 days in space, including 159 aboard the ISS. He explained that the systems were not perfect in containing every possible odor.

“Oleg Kotov, my Expedition 15 Russian crewmate and our Soyuz commander, liked to stash his used workout clothes above the forward-facing FGB (Functional Cargo Block, Russian Module) hatch,” Anderson said. “This was not my favorite choice for the stowage of sweaty workout gear as there was not a very good chance that they would dry out effectively.”

Anderson explained that he preferred to dry his sweaty workout clothes in front of an air conditioning vent that ensured that the water vapor from his sweat would be recapured quickly and turned into drinking water. He noted also that space has its own smell that permeates the ISS, and he likened it to the smell of arc welding or the burning of ozone.