CRCST hydrogen peroxide and low-temperature sterilization practice questions, with every answer explained

1. Cotton is cellulose, which absorbs peroxide and can abort the cycle
2. Cotton towels must be used only in ethylene oxide sterilizer loads
3. Cotton has to be dampened slightly before going into a peroxide load
4. Cotton is fine, but the nonwoven outer wrap has to be removed first

Answer: A. Hydrogen peroxide systems cannot process cellulose materials such as cotton, linen, or paper. Cellulose absorbs the hydrogen peroxide, which can cause the cycle to abort or leave the device without adequate sterilant contact.

Why not B: Towels are not required for EtO either. The issue is that cellulose is incompatible with hydrogen peroxide.

Why not C: Moisture also causes peroxide cycles to abort, so dampening the cotton makes the problem worse.

Why not D: The nonwoven wrap is the compatible part. The cotton towel is the item that must go.

Exam tactic: Peroxide hates cellulose: no paper, linen, or cotton.

1. A standard paper and plastic pouch used for steam loads
2. A paper pouch that has been folded over twice and taped shut
3. Any peel pouch, as long as it is double pouched for strength
4. A pouch made of synthetic, non-cellulose material and plastic

Answer: D. Pouches for hydrogen peroxide systems must be made of synthetic, non-cellulose material, such as a polyolefin and plastic pouch labeled for that process. Paper pouches absorb the sterilant and are not compatible.

Why not A: Standard steam pouches have a paper side, and paper is cellulose that absorbs hydrogen peroxide.

Why not B: Paper is incompatible, and folding pouches is not an acceptable packaging practice.

Why not C: Double pouching does not fix incompatible material. A paper pouch remains cellulose.

Exam tactic: Peroxide pouch = synthetic web, no paper.

1. The items in the load were completely dry
2. Moisture was left on one or more items
3. The load was packaged in synthetic wraps
4. The load contained an internal indicator

Answer: B. Items must be completely dry before a hydrogen peroxide cycle. If moisture is present on the objects, the required vacuum cannot be achieved and the cycle aborts.

Why not A: Dry items are what the system requires, so dryness does not cause an abort.

Why not C: Synthetic, non-cellulose wraps are the correct packaging for this process.

Why not D: Internal chemical indicators made for hydrogen peroxide are expected in each package.

Exam tactic: Wet load in peroxide = cycle abort.

1. Yes, if the vial cap is removed so the vapor can enter
2. Yes, if the cycle is extended to the longest setting
3. No, because liquids cannot be processed in this system
4. No, unless the vial is wrapped in a linen towel first

Answer: C. Hydrogen peroxide gas systems cannot process liquids. Liquids interfere with the vacuum and with sterilant contact, and the system is designed only for clean, dry devices listed in their IFU.

Why not A: Opening the vial makes things worse, since the liquid would disrupt the cycle and absorb sterilant.

Why not B: Cycle length does not make a liquid compatible with this process.

Why not D: Linen is cellulose and also incompatible. The answer is no regardless of wrapping.

Exam tactic: No liquids in a peroxide chamber.

1. Bacillus atrophaeus
2. Geobacillus stearothermophilus
3. Escherichia coli
4. Mycobacterium tuberculosis

Answer: B. Hydrogen peroxide sterilizers are monitored with biological indicators containing Geobacillus stearothermophilus spores, the same organism used for steam.

Why not A: Bacillus atrophaeus is the BI organism for ethylene oxide and dry heat.

Why not C: Escherichia coli is a vegetative bacterium, far too easy to kill to challenge a sterilizer.

Why not D: Mycobacterium tuberculosis is used to rate disinfectants, not as a sterilizer BI.

Exam tactic: Peroxide shares the steam bug: stearothermophilus.

1. The sterilant breaks down into water vapor and oxygen
2. The sterilant stays inside the sealed package
3. The packaging absorbs all leftover peroxide
4. The cycle runs at a high steam temperature

Answer: A. The byproducts of a hydrogen peroxide gas plasma cycle, water vapor and oxygen, are nontoxic. That is why no aeration phase is needed, which is a major advantage over ethylene oxide.

Why not B: Sterilant is not meant to remain in the package. The process leaves nontoxic byproducts.

Why not C: Packaging is not meant to absorb peroxide. Absorbent cellulose packaging is incompatible.

Why not D: The process is low temperature, not a steam cycle.

Exam tactic: Peroxide leaves water and oxygen. No aeration.

1. A tray validated for that process, with no paper or cellulose liner
2. Any steam tray, if a paper tray liner is added to absorb moisture
3. A tray lined with a cotton towel to protect delicate instruments
4. Any tray, because tray material has no effect on this process

Answer: A. Trays and accessories for hydrogen peroxide must be validated for that process and free of cellulose. Paper liners or cotton towels absorb the sterilant, and some tray materials are not compatible, so the tray IFU must list the system.

Why not B: Paper liners are cellulose and absorb peroxide, so they are incompatible.

Why not C: Cotton is cellulose. It absorbs the sterilant and can abort the cycle.

Why not D: Tray materials and design affect sterilant contact, so the tray must be validated for the process.

Exam tactic: Peroxide tray: validated, no paper, no cotton.

1. Steam indicators are too large to fit inside peroxide packs
2. Steam indicators must be used only with a Bowie-Dick test pack
3. Steam indicators release moisture that cancels the peroxide cycle
4. Steam indicators respond only to steam conditions, not peroxide

Answer: D. Chemical indicators are designed for a specific sterilization process. A steam indicator does not react to hydrogen peroxide conditions, so it gives no meaningful information about the peroxide cycle.

Why not A: Size is not the issue. The indicator chemistry does not match the process.

Why not B: Steam CIs come in many types for production loads. The Bowie-Dick pack is only one specific test.

Why not C: Steam indicators do not release moisture. They simply do not respond to peroxide.

Exam tactic: Match the indicator to the sterilant.

1. A short cycle with no aeration and nontoxic byproducts
2. It can process liquids, linens, and paper packaged items
3. It penetrates long, narrow lumens better than any method
4. It needs no biological monitoring once it is installed

Answer: A. Hydrogen peroxide cycles are short, roughly 16 to 75 minutes depending on the sterilizer model and cycle selected, and leave only water vapor and oxygen, so items are ready without aeration. EtO needs a long cycle plus hours of aeration and involves a toxic, carcinogenic gas.

Why not B: Hydrogen peroxide cannot process liquids or cellulose such as linen and paper.

Why not C: Lumen penetration is limited by length and diameter in peroxide systems, so it is not superior to all methods.

Why not D: Hydrogen peroxide sterilizers require routine biological monitoring like other sterilizers.

Exam tactic: Peroxide = fast and clean. EtO = slow and toxic.

1. Placed in sterile storage until the next scheduled case
2. Used promptly, since it comes out wet and unwrapped
3. Wrapped in a nonwoven wrap and stored for up to a week
4. Air dried on a counter, then pouched for later use

Answer: B. Liquid chemical sterilant systems process unwrapped, immersed devices, so items come out wet and unpackaged. They are intended for just in time use and are transferred to the point of use and used promptly, not stored as sterile items.

Why not A: Unwrapped, wet devices cannot keep sterility in storage.

Why not C: Wrapping after the cycle exposes the device to contamination and does not create a sterile package.

Why not D: Drying on a counter and pouching afterward contaminates the device. It would need full reprocessing.

Exam tactic: Liquid sterilant = just in time, never stored.