George Aldrich, whose official title is chemical specialist, works at NASA's White Sands Test Facility in New Mexico. He uses his nose to protect astronauts from unpleasant or harmful odors (气味). His near four-decade career has involved smelling objects from technical handbooks to astronauts' personal things.

    It's crucial that all items taken aboard the International Space Station (ISS) are odorless. Since astronauts are allowed to bring personal items aboard, all their objects must be smell-checked before leaving Earth. In a video provided by Science Channel, Aldrich relates one specific occasion when an astronaut wanted to build a ship in a bottle in space. Everything in the ship-building process had to be sniffed—right down to the glue.

    Aldrich and his team are responsible for making sure that objects are not only odorless but also harmless to astronauts. When the ISS heats up, a process called off-gassing occurs, which means chemicals flow out from certain substances (物质). Objects that would be safe on Earth could give off unpleasant odors or become dangerous when exposed to high temperatures in the ISS's unique environment.

    Of course, humans aren't the only testers or the first to be exposed to potentially dangerous objects. Before Aldrich sticks his nose into a substance, it has been examined by machines. Even though machines can detect unsafe substances, computers cannot tell exactly how things smell to humans. While something could be technically fine, it could be smelly to an astronaut.

Aldrich's nose is not alone there. He is the head of a hard-sniffing team of smell testers. Together they smell each object and rate it on a scale (等级) of 1 to 4. According to NASA, 1 cannot be detected, and 4 is considered not bearable. After the scientists conclude their tests, the scores are averaged. If an item is rated more than 2.4 on the scale, it fails the test and is not allowed on the flight.