Before preheating the autoclave, it should be checked for which of the following?

• A. Calibration of the thermometer
• B. Adequate water level in the chamber
• C. Presence of microbial cultures
• D. Correct labeling of glassware

Answer: (B)

Verified step by step guidance

1. Understand the purpose of an autoclave: it is used to sterilize equipment and media by applying high-pressure saturated steam.
2. Recognize that before preheating, the autoclave must have an adequate water level in the chamber to generate the necessary steam for sterilization.
3. Consider why other options are less appropriate: calibration of the thermometer is important but usually checked during maintenance, presence of microbial cultures should not be inside before sterilization, and labeling of glassware is unrelated to autoclave operation.
4. Conclude that checking the adequate water level ensures the autoclave can function properly and achieve sterilization conditions.
5. Therefore, the critical preheating check is to verify the adequate water level in the chamber.