Paper I — 2019 July (Supplementary) (2010 Scheme) — Q4
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Paper I
2019 July (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Gaseous disinfectants
Q42 marksShort Notes
Answer
Gaseous disinfectants/sterilants are chemical agents in gaseous form used to sterilize/disinfect heat-labile items (plastics, electronic equipment, delicate instruments) that would be damaged by moist or dry heat, by penetrating packaging and reaching all surfaces of complex-shaped items.
Examples:
Ethylene oxide (ETO) — the most widely used gaseous sterilant in hospitals/industry; a highly penetrating, alkylating agent, killing microorganisms (including spores) by alkylating nucleic acids/proteins. Used for heat-sensitive medical devices, plastic disposables, catheters, and electronic equipment; requires controlled temperature/humidity/gas concentration and a prolonged aeration period afterward (flammable, explosive, carcinogenic, irritant).
Formaldehyde gas — used for fumigation of enclosed spaces (operation theatres, isolation wards, safety cabinets) and low-temperature steam-formaldehyde sterilization; pungent, irritant, suspected carcinogen, limiting current use.
Hydrogen peroxide gas plasma/vaporized hydrogen peroxide — a modern, low-toxicity alternative for sterilizing heat/moisture-sensitive instruments (e.g., endoscopes); leaves no toxic residue.
Beta-propiolactone — used for sterilizing vaccines/biological products and room fumigation, largely superseded due to toxicity concerns.
Common principle: typically act by alkylation of nucleic acids and proteins, disrupting replication and essential cellular functions, chosen specifically to achieve sterilization at low temperature, avoiding heat/moisture damage.
