**Question:** Temperature and time period in hot air oven is

A. 120°C for 30 minutes
B. 100°C for 60 minutes
C. 150°C for 20 minutes
D. 180°C for 45 minutes

**Core Concept:** Heat treatment in a hot air oven is a sterilization technique used to inactivate microorganisms on various materials or surfaces, including medical devices, vaccines, and drugs. The process involves exposing the items to a specific temperature and time period to ensure the destruction of microorganisms effectively.

**Why the Correct Answer is Right:** The correct answer is **B. 100°C for 60 minutes**, as this combination provides the most appropriate conditions for heat treatment. In a hot air oven, temperatures above 100°C are generally used for sterilization, but 100°C is often chosen due to practical considerations, such as energy efficiency and equipment capabilities. Longer exposure times (60 minutes) are necessary to ensure the complete destruction of microorganisms, especially for heat treatment.

**Why Each Wrong Option is Incorrect:**

A. **120°C for 30 minutes** is too low a temperature (120°C is close to the boiling point of water) and insufficient duration for sterilization.
C. **150°C for 20 minutes** is a higher temperature than necessary and may cause degradation or damage to the treated object.
D. **180°C for 45 minutes** is too high a temperature, which may lead to chemical reactions causing degradation and altering the properties of the treated item. Additionally, a longer duration (45 minutes) may not be necessary as the higher temperature already ensures effective sterilization.

**Clinical Pearl:** To ensure safe and effective heat treatment, use a temperature between 100-120°C and a duration of at least 60 minutes for complete microbial inactivation. Adjusting the temperature only or the duration alone may result in inadequate sterilization or damage to the treated item.