Why Sterilization Is the Highest-Tested Topic on the CRCST Exam
The Sterilization Process domain accounts for 21% of the CRCST exam — tied for the highest with decontamination and prep & pack. You must know every sterilization method, its parameters, advantages, limitations, and monitoring requirements.
Steam Sterilization (Autoclave)
Steam sterilization is the most common and preferred method in sterile processing. It uses moist heat under pressure to kill all microorganisms including spores.
Steam Sterilization Parameters
| Cycle Type | Temperature | Time |
|---|---|---|
| Gravity displacement | 250°F (121°C) | 30 minutes |
| Pre-vacuum (prevac) | 270°F (132°C) | 4 minutes |
| Flash (IUSS) | 270°F (132°C) | 3 minutes (unwrapped) |
Key Steam Sterilization Facts
- Requires direct steam contact with all surfaces
- Items must be clean and dry before sterilization
- Biological indicator: Geobacillus stearothermophilus spores
- Cannot be used for: heat-sensitive items, moisture-sensitive items, implants (without BI release)
Ethylene Oxide (ETO) Sterilization
ETO is used for heat-sensitive and moisture-sensitive items that cannot withstand steam.
ETO Key Facts
- Sterilizes at low temperatures (room temperature to 60°C)
- Requires a long aeration period (8–12 hours) to off-gas toxic residue
- Biological indicator: Bacillus atrophaeus spores
- ETO is toxic and carcinogenic — requires proper ventilation and monitoring
- Cycle time: several hours including aeration
Hydrogen Peroxide Gas Plasma Sterilization
A low-temperature sterilization method ideal for moisture and heat-sensitive devices.
Key Facts
- Trade name: STERRAD (Advanced Sterilization Products)
- Temperature: 50°C or less
- No toxic residuals — safe for immediate use after cycle
- Cannot process: linens, liquids, cellulose-based materials (paper), long narrow lumens
- Biological indicator: Geobacillus stearothermophilus spores
- Cycle time: approximately 28–75 minutes
Dry Heat Sterilization
Used for items that cannot be penetrated by steam or damaged by high temperatures — such as powders, oils, and sharp instruments.
Key Facts
- Higher temperature required than steam: 320°F (160°C) for 2 hours
- No moisture involved — kills by oxidation
- Very long cycle times
- Rarely used in modern sterile processing departments
Peracetic Acid (Steris System)
Used for immediate-use sterilization of heat-sensitive instruments.
Key Facts
- Trade name: STERIS System 1E
- Liquid chemical sterilant — instruments must be used immediately (no sterile storage)
- Cannot be used for implants
- Biological indicator: Bacillus atrophaeus or Geobacillus stearothermophilus
Sterility Assurance Monitoring
Every sterilization method must be monitored at three levels:
1. Mechanical Monitors
Printouts and gauges on the sterilizer showing time, temperature, and pressure. Checked every cycle.
2. Chemical Indicators (CI)
- Class 1 — Process indicators (autoclave tape) — confirm item was exposed to sterilization process
- Class 5 — Integrating indicators — most reliable chemical indicator, responds to all critical parameters
- Class 6 — Emulating indicators — cycle-specific
3. Biological Indicators (BI)
- Most reliable test of sterilization effectiveness
- Contains live spores — must be incubated after cycle
- Must be run: daily, with every implant load, and with every ETO load
- Positive BI = sterilization failure — recall protocol initiated
Sterility Assurance Level (SAL)
The SAL is the probability of a single viable microorganism on a sterilized item. The accepted SAL for sterile medical devices is 10⁻⁶ — meaning 1 in 1,000,000 chance of contamination.
Common CRCST Sterilization Exam Questions
Q: Which biological indicator is used to monitor steam sterilization?
A: Geobacillus stearothermophilus
Q: What is the minimum exposure time for a pre-vacuum steam cycle at 270°F?
A: 4 minutes
Q: Which items CANNOT be processed in a hydrogen peroxide plasma sterilizer?
A: Cellulose (paper), linens, liquids, and long narrow lumens
Q: When MUST a biological indicator be run?
A: Daily, with every implant load, and with every ETO load
Practice all sterilization topics with our 450+ CRCST practice questions — covering every sterilization method tested on the official HSPA exam.
Official Resources
- CDC Guideline for Disinfection and Sterilization in Healthcare Facilities — CDC reference for all sterilization methods and monitoring
- AAMI ST79 — Steam Sterilization Standard — ANSI/AAMI standard for steam sterilization of medical devices
- HSPA CRCST Exam Content Outline — Official sterilization domain breakdown