CRCST Sterilization Practice Questions (2026): 15 Free Questions with Answers

15 Free CRCST Sterilization Questions, Answered and Explained

Work through all 15 questions below. Every answer includes an explanation that cites its source. When you finish, head back to the full 50-question practice test.

1. Sterilization

   Question 1: In a pre-vacuum (dynamic air removal) steam sterilizer at 275 degrees F (135 degrees C), the minimum exposure time for wrapped instrument trays is:

   • A) 10 minutes
   • B) 3 minutes
   • C) 18 minutes
   • D) 45 minutes
   Answer and explanation

   Correct answer: B

   Higher temperature means shorter exposure. At 275 degrees F (135 degrees C), AAMI ST79 lists 3 minutes as the minimum exposure for wrapped goods in a pre-vacuum cycle, with drying time afterward. (Source: AAMI ST79)

2. Sterilization

   Question 2: For gravity-displacement steam sterilization of wrapped instruments at 270 degrees F (132 degrees C), the minimum exposure time is:

   • A) 4 minutes
   • B) 15 minutes
   • C) 3 minutes
   • D) 60 minutes
   Answer and explanation

   Correct answer: B

   Gravity cycles remove air passively, so they need longer exposures than pre-vacuum cycles at the same temperature. At 270 degrees F (132 degrees C), wrapped goods require 15 minutes of exposure. (Source: AAMI ST79)

3. Sterilization

   Question 3: For dry-heat sterilization of wrapped instruments at 340 degrees F (171 degrees C), the minimum exposure time is:

   • A) 10 minutes
   • B) 30 minutes
   • C) 1 hour
   • D) 4 hours
   Answer and explanation

   Correct answer: C

   Dry heat kills by oxidation, which is slower than moist heat, so exposures run much longer. At 340 degrees F (171 degrees C), wrapped instruments need 1 hour of exposure. (Source: AAMI ST79)

4. Sterilization

   Question 4: Biological indicators used to monitor ethylene oxide sterilization contain spores of:

   • A) Geobacillus stearothermophilus
   • B) Bacillus atrophaeus
   • C) Clostridium difficile
   • D) Mycobacterium tuberculosis
   Answer and explanation

   Correct answer: B

   Each sterilization method gets a BI organism chosen for its resistance to that method. Bacillus atrophaeus spores resist ethylene oxide, while Geobacillus stearothermophilus is the steam and hydrogen peroxide indicator organism. (Source: AAMI ST79)

5. Sterilization

   Question 5: Which item must NEVER be processed in a hydrogen peroxide gas plasma sterilizer?

   • A) A stainless steel hemostat
   • B) An item containing cellulose, paper, or cotton
   • C) A titanium orthopedic reamer
   • D) A single-channel flexible endoscope cleared for the system
   Answer and explanation

   Correct answer: B

   Hydrogen peroxide gas plasma cannot penetrate cellulose-based materials, which absorb the sterilant, and liquids or powders are also incompatible. Only devices and packaging validated for the specific system may be processed. (Source: AAMI ST79)

6. Sterilization

   Question 6: The Bowie-Dick test is used only on dynamic air removal (pre-vacuum) sterilizers, not gravity sterilizers, because:

   • A) Gravity sterilizers never fail
   • B) The test specifically detects air removal failures and air leaks in pre-vacuum systems
   • C) Bowie-Dick packs melt in gravity cycles
   • D) Gravity sterilizers use a different chemical indicator
   Answer and explanation

   Correct answer: B

   The Bowie-Dick test pack is an air-removal challenge. Gravity sterilizers do not mechanically remove air, so the test has nothing to challenge; it belongs to pre-vacuum cycles where trapped air is the failure mode it was designed to catch. (Source: AAMI ST79)

7. Sterilization

   Question 7: When loading a steam sterilizer, packs and trays must be positioned so that:

   • A) They touch the chamber walls for stability
   • B) Steam can circulate freely around every package and nothing touches the chamber walls
   • C) The heaviest trays sit directly on the drain
   • D) Peel pouches lie flat in stacks
   Answer and explanation

   Correct answer: B

   Sterilization happens where steam touches. Packs pressed against walls or each other create cold spots where air and condensate collect, so loads are arranged with space for circulation and kept off the chamber walls. (Source: AAMI ST79)

8. Sterilization

   Question 8: After the exposure phase of a steam cycle ends, wrapped trays need:

   • A) Immediate unloading while still hot to save time
   • B) A drying phase before the door is opened, so packages come out dry
   • C) A cold water rinse to cool them quickly
   • D) No further time in the chamber
   Answer and explanation

   Correct answer: B

   Exposure kills microorganisms, but the cycle is not finished until the load is dry. Opening the door early or skipping dry time leaves damp packages, and a wet pack is a contaminated pack. (Source: AAMI ST79)

9. Sterilization

   Question 9: Superheated steam is undesirable in a steam sterilizer because:

   • A) It is too hot and melts packaging
   • B) It is too dry to transfer heat effectively and kill microorganisms
   • C) It uses more water than saturated steam
   • D) It damages the chamber walls
   Answer and explanation

   Correct answer: B

   Sterilization by steam depends on moisture carrying heat into proteins and denaturing them. Superheated steam behaves more like dry hot air, which kills far more slowly, so sterilizers are designed to deliver saturated steam at 97 to 100 percent quality. (Source: AAMI ST79)

10. Sterilization

    Question 10: The steam trap (thermostatic trap) on a steam sterilizer exists to:

    • A) Trap instruments that fall during loading
    • B) Remove condensate and air from steam lines and the chamber
    • C) Measure the chamber temperature
    • D) Filter detergent from the steam
    Answer and explanation

    Correct answer: B

    Condensate pooling in the chamber creates wet packs, and trapped air blocks steam contact. The trap continuously drains water and vents air so only dry, saturated steam reaches the load. (Source: AAMI ST79)

11. Sterilization

    Question 11: Physical monitoring of every steam sterilization cycle requires verifying and documenting:

    • A) Only the cycle start time
    • B) Time, temperature, and pressure
    • C) The color of the external indicator only
    • D) The operator name and nothing else
    Answer and explanation

    Correct answer: B

    Time, temperature, and pressure are the physical critical variables of steam sterilization. The sterilizer printout or digital record must show all three stayed within specifications for the full exposure. (Source: AAMI ST79)

12. Sterilization

    Question 12: A biological indicator comes back positive (growth). What must happen next?

    • A) Nothing, one positive BI is considered normal
    • B) Re-run the BI to see if it was a mistake, then release the load
    • C) Treat the sterilizer as failed: do not use it, investigate, and recall items processed since the last negative BI
    • D) Release the load because the chemical indicators changed
    Answer and explanation

    Correct answer: C

    A positive BI means sterilization conditions were not achieved. The sterilizer is taken out of service until the cause is found and corrected, and every load back to the last negative BI is recalled, because none of those loads can be trusted. (Source: AAMI ST79)

13. Sterilization

    Question 13: Instruments processed by immediate-use steam sterilization (IUSS) must be:

    • A) Packaged, labeled, and stored for later use
    • B) Used immediately for the patient need at hand and never stored
    • C) Resterilized in a full cycle before use
    • D) Cooled for one hour before the procedure
    Answer and explanation

    Correct answer: B

    IUSS skips the packaging and storage safeguards of terminal sterilization, so its products have no sterile barrier. The items go directly to the point of use; anything not used is reprocessed, never shelved. (Source: AAMI ST79)

14. Sterilization

    Question 14: A Type 6 chemical indicator is best described as:

    • A) An external process indicator
    • B) An emulating indicator that responds to all critical variables for one specified sterilization cycle
    • C) A biological indicator
    • D) A Bowie-Dick test
    Answer and explanation

    Correct answer: B

    Type 6 emulating indicators are cycle-specific: they react to every critical variable of one defined cycle, such as 4 minutes at 270 degrees F in pre-vacuum steam. They are the most cycle-precise chemical monitors available. (Source: AAMI ST79)

15. Sterilization

    Question 15: A process challenge device (PCD) used with a biological indicator is designed to:

    • A) Make the BI easier to kill so cycles pass faster
    • B) Represent the hardest-to-sterilize location in the load, challenging the BI
    • C) Replace the need for chemical indicators
    • D) Sterilize the instruments inside it
    Answer and explanation

    Correct answer: B

    A PCD places the BI inside a test pack that mimics the most resistant spot in the load, such as the center of a dense tray. If sterilant reaches and kills the BI there, the rest of the load can be trusted. (Source: AAMI ST79)

Back to the full 50-question free CRCST practice test

Sources

Every explanation on this page cites one of the references below. Always follow your facility's policies and the manufacturer instructions for use.

• AAMI ST79, Comprehensive guide to steam sterilization and sterility assurance in health care facilities. Association for the Advancement of Medical Instrumentation.
• OSHA 29 CFR 1910.1030, Bloodborne Pathogens standard. U.S. Occupational Safety and Health Administration.
• CDC Guideline for Disinfection and Sterilization in Healthcare Facilities (2008, updated 2019). Centers for Disease Control and Prevention.
• HSPA CRCST Exam Content Outline. Healthcare Sterile Processing Association.

Not affiliated with or endorsed by HSPA.