General microbiology and sterilisation: operation theatre fumigation: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · General microbiology and sterilisation: operation theatre fumigation

Sample item

After a cluster of postoperative wound infections, a sealed operation theatre is fumigated overnight by adding potassium permanganate crystals to a liquid placed in open trays. Which agent is released and acts as the fumigant?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Formaldehyde gas

Operation theatres are classically fumigated with formaldehyde, produced by adding potassium permanganate to formalin. The room must be sealed and left for many hours, then neutralised with ammonia before reuse. Ethylene oxide is used in closed sterilising chambers for heat-labile articles, not for room fumigation.

Option by option

  • A. Sulphur dioxide

    Sulphur dioxide comes from burning sulphur and is not the usual theatre fumigant.

  • B. Chlorine gas

    Chlorine is released from hypochlorite or bleaching powder with acid, not from permanganate with a liquid disinfectant.

  • C. Ethylene oxide

    Ethylene oxide is a gas supplied from cartridges for chamber sterilisation of heat-sensitive items, not generated by permanganate.

  • D. Formaldehyde gas (correct)

    Correct. Permanganate oxidises formalin and drives off formaldehyde vapour, which kills organisms on surfaces and in air.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is D, Formaldehyde gas. Operation theatres are classically fumigated with formaldehyde, produced by adding potassium permanganate to formalin.

Why is "Sulphur dioxide" not the answer?

Sulphur dioxide comes from burning sulphur and is not the usual theatre fumigant.

Why is "Chlorine gas" not the answer?

Chlorine is released from hypochlorite or bleaching powder with acid, not from permanganate with a liquid disinfectant.

Why is "Ethylene oxide" not the answer?

Ethylene oxide is a gas supplied from cartridges for chamber sterilisation of heat-sensitive items, not generated by permanganate.

What concept does this question test?

It tests General microbiology and sterilisation: operation theatre fumigation in Microbiology. The room must be sealed and left for many hours, then neutralised with ammonia before reuse. Ethylene oxide is used in closed sterilising chambers for heat-labile articles, not for room fumigation.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study General microbiology and sterilisation: operation theatre fumigation?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.