Editing Cold trap (section)

== Hazards ==
Care should be taken when using a cold trap not to condense oxygen gas into the cold trap, visible as light blue liquid. Liquid oxygen is potentially explosive, and this is especially true if the trap has been used to trap solvent. Oxygen can be condensed into a cold trap if a pump has sucked air through the trap when the trap is very cold, e.g. when cooled with [[liquid nitrogen]]. Besides oxygen, many hazardous gases emitted in reactions, e.g. [[sulfur dioxide]], [[chloromethane]], condense into cold traps.