CRCST washer-disinfectors and ultrasonic cleaning practice questions, with every answer explained

1. Thermal rinse, prewash, drying, enzyme, wash, rinse, lubrication
2. Wash, drying, prewash, lubrication, rinse, enzyme, thermal rinse
3. Prewash, enzyme, wash, rinse, thermal rinse, lubrication, drying
4. Drying, enzyme, prewash, thermal rinse, wash, rinse, lubrication

Answer: C. A typical cycle runs a cold prewash, an enzymatic soak, a detergent wash, a rinse, a thermal rinse that disinfects with hot water, an instrument lubricant phase when programmed, and hot air drying. The exact phases and parameters depend on the cycle and the washer IFU.

Why not A: The thermal rinse disinfects at the end, not before soil is removed.

Why not B: Drying before the prewash and thermal rinse makes no sense, since wet phases follow.

Why not D: Drying always comes last, after all wet phases.

Exam tactic: Cold, enzyme, wash, rinse, hot rinse, lube, dry.

1. Shadowing of items below, plus water pooling in the basin
2. Overheating of the thermal rinse water
3. Excess lubricant on the small instruments
4. No problem, because the spray reaches every rack of the load equally

Answer: A. Large items can block or shadow spray from reaching items next to or beneath them. A basin placed upright also holds water instead of draining. Basins and other concave items are positioned tilted or inverted, and large items are placed so they do not block the spray arms or other items.

Why not B: Load position does not change the temperature of the thermal rinse.

Why not C: Lubricant dosing is controlled by the washer, not by basin position.

Why not D: Spray is directional, and shielded items are not cleaned.

Exam tactic: Concave side down, and nothing big shading the little stuff.

1. That the arms are tightened so they cannot move
2. That the arms rotate freely and their nozzles are not clogged
3. That the arms are coated with lubricant
4. That the arms are removed for the first cycle

Answer: B. Spray arms must spin freely and their nozzles must be open to deliver water and detergent across the load. Debris or a blocked nozzle leaves part of the load uncleaned. Items in the load must also not touch or block the arms during rotation.

Why not A: Spray arms are designed to rotate, and a fixed arm cleans only one area.

Why not C: Lubricant on the arms would interfere with cleaning and is not a check item.

Why not D: Spray arms must be in place for every cycle.

Exam tactic: Spin free, holes clear.

1. By heating the solution until the soil melts off the surface
2. By spraying high-pressure jets of detergent
3. By cavitation, as tiny bubbles implode against surfaces
4. By tumbling instruments against each other

Answer: C. Ultrasonic cleaners convert high frequency sound waves into energy that forms millions of tiny bubbles in the solution. The bubbles collapse, or implode, and dislodge fine soil from crevices, serrations, and hinges that brushes cannot reach. This process is called cavitation.

Why not A: Heat is not the cleaning mechanism of an ultrasonic unit.

Why not B: Spray jets are used in washer-disinfectors, not ultrasonic cleaners.

Why not D: Instruments are placed in a basket and do not tumble, which would damage them.

Exam tactic: Ultrasonic = cavitation = bubbles that implode.

1. To keep the solution warm
2. To contain aerosols created by cavitation
3. To increase the frequency of the sound waves
4. To prevent the instruments from floating

Answer: B. Cavitation creates contaminated aerosols above the solution. Keeping the lid closed during operation contains these aerosols and protects the technician. Items are also fully submerged so the entire surface is cleaned.

Why not A: The lid is a safety measure against aerosols, not a heating feature.

Why not C: The lid has no effect on the sound wave frequency.

Why not D: Instruments sit in a basket below the surface and the lid does not hold them down.

Exam tactic: Bubbles pop, aerosols fly. Lid down.

1. It shifts the pH of the solution so that it becomes strongly acidic
2. Ions can transfer between metals and cause etching or plating
3. It turns off the degas function
4. It makes the cycle run twice as long

Answer: B. When dissimilar metals share an ultrasonic bath, ions can transfer from one metal to the other, leading to etching, deposits, or plating on the instruments. Metals are separated into different loads, and chrome-plated or other special items are processed only as their IFU allows.

Why not A: The concern is metal ion transfer, not a pH shift of the solution.

Why not C: Basket contents do not affect the degas function.

Why not D: Mixed metals do not change cycle length.

Exam tactic: Same metal, same bath. Mixed metals swap ions.

1. Place them in directly because cavitation removes all soil
2. Run them twice in the ultrasonic instead of brushing
3. Use the ultrasonic as the final disinfection step
4. Remove gross soil first, then use the ultrasonic for fine soil

Answer: D. Ultrasonic cleaning is designed to remove fine soil from crevices after gross soil has been removed by manual or mechanical cleaning. Heavy soil absorbs cavitation energy and contaminates the solution quickly. After ultrasonic cleaning, items are rinsed to remove loosened debris and solution.

Why not A: Heavy soil overloads the bath and reduces cavitation for everything in it.

Why not B: Repeating the cycle does not replace removing gross soil.

Why not C: Ultrasonic cleaners clean but do not disinfect or sterilize.

Exam tactic: Gross soil first, ultrasonic for the fine stuff, then rinse.

1. When visibly soiled, or as the manufacturer and policy direct
2. Only at the end of each week, regardless of use
3. Only after the unit fails its scheduled degas cycle
4. Whenever the solution cools below its set operating temperature range

Answer: A. Ultrasonic solution collects soil and organisms with each load, which reduces cleaning and can recontaminate items. It is changed when visibly soiled and at the intervals the manufacturer and facility policy set. Fresh solution is then degassed before use.

Why not B: A fixed weekly change ignores how quickly the solution becomes soiled.

Why not C: Degassing is done on fresh solution and is not the trigger for changing it.

Why not D: Temperature is not the indicator for changing soiled solution.

Exam tactic: Dirty bath = new bath, then degas.

1. To sterilize case carts before they return to the OR
2. To clean surgical instruments in large batches
3. To clean and disinfect case carts, bins, and large items
4. To dry wrapped trays after steam sterilization

Answer: C. Cart washers are large chamber washers that clean and disinfect case carts, transport bins, rigid containers, and other large items with detergent and hot water. Carts that carry soiled items are cleaned before they are used again for clean or sterile items.

Why not A: Cart washers clean and disinfect but do not sterilize.

Why not B: Instruments are processed in instrument washers, not cart washers.

Why not D: Sterilized packs are never sent through a washer.

Exam tactic: Cart washer = car wash for carts and bins.

1. Sterile and ready for the OR once dry
2. Safe to handle, but not yet sterile
3. High-level disinfected and ready for use on sterile tissue
4. Contaminated and must be manually cleaned again

Answer: B. The thermal rinse in a washer-disinfector provides disinfection that makes items safe for staff to handle in prep and pack. It is not sterilization. Critical instruments that enter sterile tissue still must be inspected, packaged, and sterilized.

Why not A: A washer-disinfector does not sterilize.

Why not C: Critical items require sterilization, not disinfection.

Why not D: A completed cycle with clean results does not require repeat manual cleaning.

Exam tactic: Washer-disinfector = safe to handle, not safe for the patient yet.