Sterilization Methods for the CRCST Exam
Updated October 27, 2026
The Sterilization Process is about a fifth of the CRCST exam. You need to know how each sterilization method works, what it’s used for and its limits. Here’s an overview, followed by free practice questions. Questions follow AAMI standards, such as ST79 for steam and ST41 for ethylene oxide; at work, the device’s instructions for use (IFU) and the sterilizer manufacturer’s instructions decide the cycle.
Steam sterilization
Steam under pressure is the most common, fastest and least expensive method for heat- and moisture-tolerant items. It needs four things: steam, pressure, temperature and time, and steam must contact every surface, which means air must be removed.
| Cycle type | How air is removed |
|---|---|
| Gravity displacement | Steam pushes air down and out of a drain by gravity |
| Dynamic air removal (prevacuum) | Vacuum pulses actively remove air before sterilizing, which allows shorter cycles |
The exact temperature and exposure time depend on the cycle, the load and the device’s IFU. Common examples are about 250°F (121°C) for gravity cycles and about 270°F to 275°F (132°C to 135°C) for dynamic air removal cycles, each with its own exposure time.
Low-temperature methods
For items that can’t take the heat or moisture of steam:
| Method | Key points |
|---|---|
| Ethylene oxide (EO) | Penetrates well and works on many materials, but is toxic; items need aeration to remove residual gas, and cycles are long |
| Hydrogen peroxide (vaporized, or with gas plasma) | Fast, leaves no toxic residue; not compatible with cellulose items such as paper, linen and cotton, which absorb the hydrogen peroxide |
Loading basics
- Don’t overload; leave space for the sterilant to circulate.
- Place peel pouches on edge, paper to plastic, as your procedure directs.
- Put heavier items on the bottom so condensate doesn’t drip onto other packs.
- Let loads cool before handling, and never put warm packs on cold surfaces (condensation can wick contamination in).
Free practice questions
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What is the most common method for sterilizing heat- and moisture-tolerant instruments?Answer: BSteam sterilization is fast, effective, nontoxic and inexpensive, so it's the first choice for items that can tolerate heat and moisture.
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How do dynamic air removal (prevacuum) sterilizers remove air from the chamber?Answer: ADynamic air removal sterilizers use mechanical vacuum pulses to remove air, so steam can quickly reach every surface.
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Why must items sterilized with ethylene oxide be aerated?Answer: CEthylene oxide is toxic, and materials absorb it. Aeration removes residual gas before items are used on patients.
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Which item is NOT compatible with hydrogen peroxide sterilization?Answer: DCellulose materials such as cotton, linen and paper absorb hydrogen peroxide, which can cause the cycle to fail.
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Why should warm sterilized packs not be placed on cold surfaces?Answer: ACooling packs on cold surfaces causes condensation, and wet packs can draw microorganisms through the packaging. Let loads cool as the procedure directs.
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What decides the exact temperature and exposure time for a steam cycle?Answer: CCycle parameters depend on the device, packaging and sterilizer, so always follow the IFU and the sterilizer manufacturer's instructions.
Pass the CRCST exam on your first try
- All 207 questions on decontamination, disinfection, instruments, packaging, sterilization, storage, patient care equipment and professional skills
- An explanation for every answer, with the AAMI standard, CDC guideline or OSHA rule behind it
- Unlimited full 125-question practice exams, with each domain in its real share