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

15 Free CRCST Decontamination 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. Decontamination

   Question 1: The decontamination area is kept cooler than the rest of the department, around 60 to 65 degrees F (16 to 18 degrees C). What is the main reason?

   • A) Cold air sterilizes instruments faster
   • B) Cooler temperatures slow microbial growth and make heavy PPE more tolerable
   • C) Ultrasonic cleaners only work below 65 degrees
   • D) OSHA requires all work areas to stay below 65 degrees
   Answer and explanation

   Correct answer: B

   Warm, humid rooms accelerate bacterial growth on soiled instruments waiting for processing, and decontamination PPE (fluid-resistant gown, heavy gloves, face shield) is exhausting in heat. AAMI ST79 recommends the cooler range for the decontamination area. (Source: AAMI ST79)

2. Decontamination

   Question 2: For manual cleaning with an enzymatic detergent, what water temperature should the sink be?

   • A) As hot as possible, near boiling, to kill microorganisms
   • B) The temperature stated in the detergent manufacturer IFU, usually warm or tepid
   • C) Ice cold, to keep the enzymes stable
   • D) It does not matter as long as there is enough detergent
   Answer and explanation

   Correct answer: B

   Water that is too hot denatures enzymes and bakes protein soil onto instruments, while cold water reduces cleaning action. The detergent IFU gives the temperature window where its enzymes work best, typically warm or tepid. (Source: AAMI ST79)

3. Decontamination

   Question 3: Before an ultrasonic cleaner is used for the first patient load of the day, the technician must degas it. How is degassing done?

   • A) Add extra detergent and run a full cleaning cycle
   • B) Fill the tank with fresh solution and run the unit empty for the time stated in the IFU
   • C) Wipe the tank interior with alcohol
   • D) Heat the tank to 200 degrees F
   Answer and explanation

   Correct answer: B

   Fresh solution holds dissolved air that absorbs ultrasonic energy and weakens cavitation. Running the unit empty for the IFU stated time drives the trapped air out so the first load gets full cleaning power. (Source: AAMI ST79)

4. Decontamination

   Question 4: When loading instruments into an ultrasonic cleaner, which practice is correct?

   • A) Pile instruments tightly so more fit per cycle
   • B) Keep instruments fully submerged, separated, and not touching each other or the tank walls
   • C) Place the heaviest trays on top of delicate instruments
   • D) Leave lumened instruments coiled above the water line
   Answer and explanation

   Correct answer: B

   Cavitation must reach every surface. Instruments touching each other or the tank create shadow zones where bubbles cannot form, and items above the solution get no cleaning at all. Baskets keep the load separated and fully immersed. (Source: AAMI ST79)

5. Decontamination

   Question 5: A washer-disinfector achieves thermal disinfection with which minimum time and temperature combination?

   • A) 160 degrees F (71 degrees C) for 30 minutes
   • B) 180 degrees F (82 degrees C) for 10 seconds
   • C) 194 degrees F (90 degrees C) for 1 minute
   • D) 212 degrees F (100 degrees C) for 5 hours
   Answer and explanation

   Correct answer: C

   Thermal disinfection in a washer-disinfector is defined by time-temperature relationships, and 194 degrees F (90 degrees C) for 1 minute is the widely recognized minimum. Higher temperatures allow shorter times per the equipment IFU. (Source: AAMI ST79)

6. Decontamination

   Question 6: After manual cleaning, how can a technician verify that instruments are actually clean before they move to assembly?

   • A) Smell each instrument for residual odor
   • B) Use a cleaning verification test such as a protein, hemoglobin, or ATP residue test
   • C) Hold them up to the light and guess
   • D) Verification is unnecessary if the water looked clear
   Answer and explanation

   Correct answer: B

   Clean to the eye is not clean to the microbe. Residue tests detect invisible protein, blood, or organic soil left on surfaces and inside lumens, proving the cleaning process worked before instruments advance to packaging. (Source: AAMI ST79)

7. Decontamination

   Question 7: Small pits are forming on stainless steel instruments. What is the most common cause?

   • A) Steam that is too pure
   • B) Chloride-containing solutions, such as saline left to dry on the instruments
   • C) Using distilled water for rinsing
   • D) Storing instruments in a dry cabinet
   Answer and explanation

   Correct answer: B

   Chloride ions attack the chromium-oxide passive layer that protects stainless steel, and dried saline concentrates the attack in one spot. Instruments exposed to saline should be rinsed promptly so chlorides never sit on the surface. (Source: AAMI ST79)

8. Decontamination

   Question 8: Aluminum instrument containers come back from the washer with dark discoloration. What likely caused it?

   • A) An alkaline detergent, which is too harsh for aluminum
   • B) Steam temperature below 250 degrees F
   • C) Using too little detergent
   • D) The containers were loaded upside down
   Answer and explanation

   Correct answer: A

   Aluminum is attacked by highly alkaline detergents, which etch and darken the metal. Aluminum items need neutral detergents and processing per the container manufacturer IFU. (Source: AAMI ST79)

9. Decontamination

   Question 9: Why must instruments be thoroughly rinsed after cleaning and before disinfection or sterilization?

   • A) Rinsing cools the instruments for handling
   • B) Detergent residue left on instruments can stain them and interfere with sterilization
   • C) Rinsing replaces the need for drying
   • D) Water pressure sharpens the instruments
   Answer and explanation

   Correct answer: B

   Detergent films bake onto surfaces in the sterilizer, causing staining and creating a barrier between the sterilant and any remaining soil. A complete rinse, finished with treated water, leaves nothing between the instrument and the sterilant. (Source: AAMI ST79)

10. Decontamination

    Question 10: Reusable cleaning brushes must be:

    • A) Used until the bristles fall out on their own
    • B) Cleaned and disinfected after use, inspected for damage, and replaced when worn
    • C) Stored wet in detergent solution between uses
    • D) Shared between decontamination and the clean assembly area
    Answer and explanation

    Correct answer: B

    A worn or contaminated brush redeposits soil instead of removing it, and damaged bristles can scratch instruments or break off inside lumens. Brushes are cleaned after each use, inspected, and retired when bristles splay, loosen, or show damage. (Source: AAMI ST79)

11. Decontamination

    Question 11: After manual cleaning of a cannulated (lumened) instrument, the technician must:

    • A) Assume the lumen is clean if the outside looks clean
    • B) Flush the lumen and confirm fluid flows freely, proving patency
    • C) Seal the lumen with tape before packaging
    • D) Fill the lumen with lubricant and leave it
    Answer and explanation

    Correct answer: B

    Lumens hide soil where eyes cannot follow. Flushing with a syringe and watching for free, unobstructed flow confirms the channel is open and clean; a blocked or sluggish lumen goes back for re-cleaning. (Source: AAMI ST79)

12. Decontamination

    Question 12: A technician figures that doubling the detergent will clean twice as fast. What is wrong with this idea?

    • A) Nothing, more detergent always cleans better
    • B) Excess detergent leaves residue that is hard to rinse off and can interfere with sterilization
    • C) Extra detergent voids the instrument warranty
    • D) Detergent concentration has no effect on cleaning
    Answer and explanation

    Correct answer: B

    Detergents are formulated to work at a specific concentration. Overdosing leaves films that resist rinsing, and the residue can stain instruments and block sterilant contact, the opposite of the intended result. (Source: AAMI ST79)

13. Decontamination

    Question 13: AAMI ST79 recommends a minimum of how many air exchanges per hour in the decontamination area?

    • A) 2
    • B) 4
    • C) 10
    • D) 25
    Answer and explanation

    Correct answer: C

    Decontamination generates aerosols, humidity, and chemical vapors from detergents and disinfectants. Ten air exchanges per hour dilute contaminants and carry moisture out, protecting both staff and the cleaning process. (Source: AAMI ST79)

14. Decontamination

    Question 14: After finishing manual cleaning, in what order should the technician remove PPE?

    • A) Mask first, then gloves, then gown
    • B) Gloves first, then eye protection or face shield, then gown, then mask
    • C) Gown first, then everything else at once
    • D) PPE can be worn into the clean assembly area
    Answer and explanation

    Correct answer: B

    Doffing starts with the most contaminated item, the gloves, and ends with the mask, which protected the airway throughout. Removing PPE before leaving the decontamination area keeps contaminants from traveling into clean zones. (Source: OSHA 29 CFR 1910.1030)

15. Decontamination

    Question 15: Gross soil should be removed from instruments before they go into the ultrasonic cleaner because:

    • A) Heavy soil absorbs ultrasonic energy and reduces cavitation cleaning
    • B) The ultrasonic tank cannot hold large trays
    • C) Detergent is too expensive to waste on dirty instruments
    • D) Soil makes the tank water change color
    Answer and explanation

    Correct answer: A

    Ultrasonic cleaning is a fine-cleaning step, not a substitute for gross soil removal. Thick blood and tissue dampen the cavitation bubbles, so pre-rinsed instruments come out far cleaner than ones loaded straight from the OR. (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.