Unsaturated chemical-vapor sterilization involves heating a chemical solution or primarily alcohol with 0.23% formaldehyde in a closed pressurized chamber. Unsaturated chemical vapor sterilization of carbon steel instruments (eg, dental burs) causes less corrosion than steam sterilization because of the low level of water present during the cycle. Instruments should be dry before sterilizing. National and local authorities should be consulted for hazardous waste disposal requirements for the sterilizing solution.