Cleaning, Decontamination and Disinfection is 21% of the scored CRCST exam. Answer 10 exam style questions on high-level disinfection and endoscopes and see exactly which concepts would cost you points on test day.
Start the 10 questions →Before placing a bronchoscope into a reusable high-level disinfectant basin, the technician dips a chemical test strip into the solution. What is the strip checking?
These questions cover minimum effective concentration, shelf life vs use life, solution management, glutaraldehyde safety and OPA. Each one shows the correct answer and why every other option is wrong, so a miss tells you exactly what to review before the CRCST.
Prefer to read first? Every question from the practice set above, with the correct answer and why each wrong option is wrong.
Answer: C. Reusable HLD solutions are diluted by water carried in on devices and weaken with use and time. The test strip verifies the active ingredient is at or above its minimum effective concentration (MEC) before the solution is used, and the result is documented.
Why not A: Temperature is checked with a thermometer or the system display, not with a concentration strip.
Why not B: Cleaning verification tests check for residual soil on devices. The MEC strip tests the solution.
Why not D: The strip does not measure skin safety or pH. It confirms the germicide concentration.
Exam tactic: MEC strip = is the soup still strong enough.
Answer: D. Shelf life is how long the product remains stable in its unopened original container. Once the product is activated or poured for use, a separate use life or reuse life begins, and the solution is discarded at whichever limit comes first.
Why not A: Reuse life starts when the solution is activated or put into use. It is not the date on the sealed jug.
Why not B: The jug date is not a count of devices. Concentration is checked with MEC strips before use.
Why not C: Test strips have their own expiration date on their own container.
Exam tactic: Shelf life on the shelf, reuse life in the basin.
Answer: C. Adding fresh solution to used solution creates a mixture with no valid activation date or reuse life and can mask a weakened solution. When the volume is too low to immerse devices, the basin is emptied, cleaned per the IFU, and refilled with fresh solution.
Why not A: Fresh solution at labeled strength is what devices are validated for. The issue is mixing, not strength.
Why not B: Devices must be completely immersed, so a low basin is a problem that topping off does not properly solve.
Why not D: Temperature requirements come from the label. The core error here is mixing new solution into old.
Exam tactic: Never top off: dump, clean, refill.
Answer: B. Glutaraldehyde vapor irritates the eyes, nose, throat, and lungs and can cause sensitization. Keeping containers closed with tight lids, using local exhaust or a ventilated hood, and good room ventilation keep vapor levels low, along with proper PPE.
Why not A: Glove type does not address vapor inhalation, and latex is not the recommended barrier for glutaraldehyde.
Why not C: Warmer solution releases more vapor and increases exposure.
Why not D: Open basins release more vapor into the breathing zone and worsen symptoms.
Exam tactic: Lid on, exhaust on.
Answer: C. OPA reacts with proteins and stains them gray, including unprotected skin, mucous membranes, and clothing. The staining shows a PPE gap, so gloves, fluid-resistant sleeves or gowns, and eye protection must be used when handling it.
Why not A: Concentration is checked with a test strip. Skin staining is a sign of exposure, not of a weak solution.
Why not B: Dilution affects concentration, not whether OPA stains skin.
Why not D: OPA stains proteins whether it is fresh or near the end of its reuse life.
Exam tactic: OPA paints proteins gray.
Answer: B. Acidic glutaraldehyde solutions are activated with an alkaline activator to reach the pH where they are most biocidal. The activation date starts the use life, so it is recorded on the container and log, and the solution is tested with an MEC strip before use.
Why not A: Diluting a ready-to-use HLD lowers it below its labeled concentration.
Why not C: The activator is mixed in per the label, not heated in a washer.
Why not D: Without activation the solution is not in its labeled effective state, and the use life cannot be tracked.
Exam tactic: Activate, date it, test it.
Answer: C. Point-of-use pre-cleaning at the bedside, wiping the insertion tube and flushing or suctioning detergent solution through the channels, keeps soil from drying and helps prevent biofilm. The scope is then transported promptly in a closed, labeled container.
Why not A: Letting soil dry in the channels makes cleaning harder and promotes biofilm.
Why not B: Delays allow organic material to dry and harden inside channels.
Why not D: HLD is never applied to a scope that has not been leak tested and manually cleaned.
Exam tactic: Wipe and suction before the scope leaves the room.
Answer: A. The leak test is done before immersion and manual cleaning to find holes or damage in the scope's covering or channels. Immersing a leaking scope lets fluid enter the internal parts, causing major damage and a hidden contamination risk.
Why not B: By this point the scope has already been immersed several times, so a leak would have caused fluid invasion.
Why not C: Testing at the end misses leaks before fluid has entered the scope.
Why not D: Many leaks are not visible, so the test is done on every scope every time.
Exam tactic: Leak test before it gets wet.
Answer: B. Flexible endoscopes are pre-cleaned at the point of use, leak tested, manually cleaned, high-level disinfected or sterilized, rinsed, dried, and stored. Each step depends on the one before it, so cleaning always comes before disinfection.
Why not A: HLD before cleaning fails because soil protects microorganisms, and pre-cleaning belongs first.
Why not C: Pre-cleaning happens at the bedside before manual cleaning, and leak testing comes before immersion.
Why not D: HLD before leak testing and manual cleaning puts the disinfectant on soil and risks fluid invasion.
Exam tactic: Pre, leak, clean, kill, rinse, dry, hang.
Answer: A. Hanging the scope vertically in a clean, ventilated cabinet lets the channels keep draining and drying. Valves and detachable parts are removed during storage, and the scope is protected from recontamination.
Why not B: Carrying cases are for transport. Coiled storage traps moisture and the case can harbor organisms.
Why not C: Lying flat with caps on traps moisture and leaves the scope exposed to contamination.
Why not D: The decontamination room is a dirty area, so clean scopes are never stored there.
Exam tactic: Hang it, vent it, pull the valves.
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