Cold Traps and Cryogenic Hazards
The primary hazard of cryogenic materials is their extremely low temperature. Cryogenic materials, and surfaces they cool, can cause severe burns if allowed to contact the skin. Wear insulating gloves and a face shield when preparing or using cryogenic liquids. Do not use liquid nitrogen or liquid air to cool a flammable mixture in the presence of air, because oxygen can condense from the air and lead to an explosion hazard. Read Appendix 3-B (Cryogenic Hazards) for more information.
Use insulated gloves when handling dry ice. Add dry ice slowly to the liquid portion of the cooling bath to avoid foaming over. Avoid lowering your head into a dry ice chest: carbon dioxide is heavier than air, and suffocation can result. Do not store dry ice or liquid nitrogen in walk-in cold rooms; carbon dioxide or nitrogen can displace and thus lower the oxygen concentration in enclosed spaces.