Air-sensitive

Air-sensitive means that a substance, like a chemical or material, doesn't like to be exposed to air because air can make it change or react. Just like how when you leave your yummy snack out for too long, it can get yucky and moldy because of the air. Some substances can even explode if they react with air! So, when scientists or researchers work with air-sensitive substances, they need to make sure that they keep them away from air by putting them in special containers or working in special rooms with controlled air conditions. It's kind of like how you need to keep your ice cream in the freezer or it will get all melty and gross!