Aldehydes are organic compounds containing terminal -CHO groups.  These are highly reactive compounds that form cross-links between the sulfhydryl, amino, hydroxyl and carboxyl groups in proteins, causing them to denature.  Aldehydes are called agents of cold sterilization, since they do not have to be warmed to work efficiently.

Gluteraldehyde is a liquid agent used commonly as a cell fixative for electron microscopy.  A 2% solution can effectively kill vegetative bacterial cells, fungi and inactivate viruses after 10 minutes.

Formaldehyde is a gas, normally dissolved at 37% concentration in water.  It is used as a tissue preservative by morticians and can be used to disinfect surgical instruments and rooms.  This compound is carcinogenic, however, so must be handled with extreme care.