a. Ethylene oxide gas
b. Formaldehyde fumigation
c. Washing with soap water
d. Carbolic acid spraying
Although heating provides the most reliable way to rid objects of all transmissible agents, it is not always appropriate, because it will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics.
-Highly-penetrative and active against bacteria, spores and viruses
-Also flammable, toxic and expensive
-Leaves toxic residue on sterilised items
-Instruments therefore need to be stored for prolonged period before use
-Suitable for heat-sensitive items
2.Chlorine bleach is another accepted liquid sterilizing agent.
Household bleach consists of 5.25% sodium hypochlorite.
It is usually diluted to 1/10 immediately before use; however to kill Mycobacterium tuberculosis it should be diluted only 1/5.
Bleach will kill many organisms immediately, but for full sterilization it should be allowed to react for 20 minutes. Bleach will kill many, but not all spores.
3.Glutaraldehyde and formaldehyde solutions are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long.
Glutaraldehyde and formaldehyde are volatile, and toxic by both skin contact and inhalation.
Formaldehyde is less expensive and has a much longer shelf life if some methanol is added to inhibit polymerization to paraformaldehyde, but is much more volatile.
Many vaccines, such as the original Salk polio vaccine, are sterilized with formaldehyde.
Fumigation [sterilization] of operation theatres:
i. Seal the room with adhesive tapes round the edges of the doors/windows and ventilators and apertures.
ii. For Each 1000 cu.ft of space place 500ml formaldehyde (40% solution) and 1000ml of water in an electric boiler. Switch on the boiler, leave the room and seal the door.
iii. Seal the room for 24 hrs.
iv. Then open the door and neutralize any residual formaldehyde.
4.Hydrogen peroxide and formic acid are mixed as needed in the Endoclens device for sterilization of endoscopes.
This device has two independent asynchronous bays, and cleans (in warm detergent with pulsed air), sterilizes and dries endoscopes automatically in 30 minutes.
Reference: Ananthanarayan’s Microbiology,8th ed.,p-37