For effective sterilization, steam in an autoclave should be at a pressure of 15 pounds per square inch for 30 minutes and at a temperature of:

1. A

   100°C

2. B

   110°C

3. C

   121°C

4. D

   131°C

Appeared in: OSSSC Nursing Officer-2021

Explanation

• 121°C, which is the standard temperature achieved in an autoclave under 15 psi of pressure.
• This combination of high temperature and moist heat (saturated steam) is necessary to denature the proteins of all microorganisms, including heat-resistant bacterial spores.
• According to the principles of physics, increasing the pressure on a liquid (water) raises its boiling point. An autoclave is essentially a pressure cooker that leverages this principle.
• The standard cycle requires this temperature to be maintained for at least 15-30 minutes to ensure that the steam penetrates the load and achieves complete sterilization.

Why Other Options Were Wrong

• Option A: 100°C is the boiling point of water at sea level. This temperature achieves disinfection but not sterilization, as it is ineffective against bacterial spores.
• Option B: 110°C is insufficient to reliably kill all microbial life, especially spores, within the standard autoclaving timeframes.
• Option D: A temperature of 131°C (or more commonly 134°C) is used in autoclaves, but it corresponds to a higher pressure of approximately 30 psi, not 15 psi. This is used for 'flash' sterilization cycles.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Sterilization parameters for an autoclave as background academic context rather than a clinical decision trigger.
• Proper sterilization is a cornerstone of infection control in healthcare, preventing healthcare-associated infections (HAIs).
• Nurses are responsible for ensuring that medical equipment is sterile before use. This includes verifying that sterilization cycles have been completed successfully, often by checking chemical or biological indicators on the packaging.
• Understanding the principles of autoclaving helps nurses troubleshoot issues and ensure patient safety. For example, an improperly loaded autoclave can prevent steam penetration, leading to sterilization failure.

How to Approach the Question

• First, identify the key terms in the question: 'autoclave', 'sterilization', 'pressure of 15 pounds per square inch', and 'temperature'.
• This is a factual recall question based on a standard infection control procedure.
• Recall the principle of an autoclave: it uses steam under pressure to raise the temperature of water above its normal boiling point.
• Access your knowledge of the standard parameters for autoclaving. The most common setting is 15 psi.
• Link the pressure of 15 psi to its corresponding temperature. The standard temperature for this pressure is 121°C.
• Evaluate the options. Eliminate 100°C (boiling/disinfection), 110°C (insufficient), and 131°C (corresponds to a higher pressure/flash cycle) to confirm 121°C is the correct answer.

Concept Tested & Keywords

• Concept Tested: Sterilization parameters for an autoclave
• Stem keywords: sterilization, autoclave, pressure, 15 pounds per square inch, temperature
• Lead-in keywords: BEST, MOST RELEVANT CLUE

Question ID

Q99q7li2qJDiJwwxsjPMvO

Copy ID

Reference Book

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) pp. 127-129, 126-128