Is krypton dangerous?
Krypton is a gas that is found in small amounts in the earth's atmosphere. Krypton's atomic structure is very stable. It has just enough electrons to fill its outer 'shell', so it doesn't tend to combine with other elements. Since it doesn't combine with other elements, it doesn't take part in chemical reactions, so it will not burn, cause corrosion, or do other chemical-like things.
It is, however, possible for krypton to hurt you. If, for example, a room were to be filled with krypton, anyone entering the room would most likely asphyxiate. This isn't because the krypton is poisonous, but because of the lack of oxygen in the room. This problem, known as Oxygen Deficiency Hazard (ODH), is one that we at Jefferson Lab have to contend with in our accelerator. Our accelerator uses large amounts of super-cold liquid helium that could potentially cause a problem in the accelerator tunnel. The tunnel is equipped with oxygen sensors that monitor the oxygen level in the tunnel and alarms sound if the oxygen level drops too low.
Steve Gagnon, Science Education Specialist (Other answers by Steve Gagnon)