Steam sterilization cycles
| Cycle and load | Exposure | Drying |
|---|---|---|
| Gravity, wrapped instruments | 30 min at 121°C (250°F), or 15 min at 132°C (270°F) | 15–30 min |
| Gravity, textile packs | 30 min at 121°C, or 25 min at 132°C | 15 min |
| Dynamic air removal, wrapped instruments | 4 min at 132°C (270°F) | 20–30 min |
| Dynamic air removal, textile packs | 4 min at 132°C | 5–20 min |
These are CDC's minimum cycle examples. Always follow the device manufacturer's instructions for use.
| Flash (immediate-use) steam, 132°C (270°F) | Gravity | Dynamic air removal |
|---|---|---|
| Nonporous items only | 3 min | 3 min |
| Nonporous and porous items mixed | 10 min | 4 min |
CDC: don't flash sterilize implanted surgical devices unless it's unavoidable.
Monitoring: Bowie-Dick, BIs and chemical indicators
- Bowie-Dick test: daily, in an empty dynamic-air-removal (prevacuum) sterilizer.
- Biological indicators: at least weekly (CDC), and every load containing implantable items.
- BI organisms: Geobacillus stearothermophilus for steam; Bacillus atrophaeus for ethylene oxide and dry heat.
- Chemical indicators: internal and external indicators with each load.
- Chemical indicator types: 1 process, 2 specific test (such as Bowie-Dick), 3 single variable, 4 multi-variable, 5 integrating, 6 emulating.
Ethylene oxide (EO)
| Item | Value |
|---|---|
| Aeration example (PVC tubing) | 12 hours at 50°C (122°F), or 8 hours at 60°C (140°F) |
| Typical cycle ranges | 37–63°C, 40–80% relative humidity, 1–6 hours exposure |
| OSHA permissible exposure limit | 1 ppm, 8-hour time-weighted average |
| OSHA excursion limit | 5 ppm averaged over 15 minutes |
| OSHA action level | 0.5 ppm, 8-hour time-weighted average |
High-level disinfection and Spaulding
- Glutaraldehyde: 2% or more for 20 minutes at 20°C (CDC); follow the label's contact time.
- Ortho-phthalaldehyde (OPA): 0.55% for 12 minutes at 20°C.
- Spaulding classes: critical items carry a high risk of infection if contaminated with any microorganism; semicritical items contact mucous membranes or nonintact skin; noncritical items contact intact skin but not mucous membranes.
Know you're ready for the CRCST before you book your date
PassPulse is built to get you through the CRCST on your first attempt. Exam style questions on every topic, every answer explained, and a readiness score that tells you when you're ready. 15 minutes a day, on your phone.
Start preparing for the CRCSTEnvironment and sterile storage
| Area | Pressure | Minimum air changes | Humidity | Temperature |
|---|---|---|---|---|
| Decontamination (soiled workroom) | Negative | 6 per hour, all exhausted outdoors | Not required | 60–73°F (16–23°C) |
| Clean assembly / workroom (prep and pack) | Positive | 4 per hour | 60% maximum | 68–73°F (20–23°C) |
| Sterile storage | Positive | 4 per hour | 60% maximum | 75°F (24°C) maximum |
Values from ANSI/ASHRAE/ASHE Standard 170-2021, Addendum o (2024), the ventilation standard for health care facilities, aligned with the 2022 FGI Guidelines. Older CDC guidance (2008) allowed sterile storage humidity up to 70%; use 60%. Temperature, humidity and air pressure should be monitored and recorded at least daily (HSPA).
- Shelving (HSPA): at least 8 inches above the floor, 18 inches below the ceiling or sprinkler heads, and at least 2 inches from outside walls.
- Event-related sterility: a sterile package can be used indefinitely unless the packaging is compromised.
- Instrument set weight: 25 pounds maximum, container or wrap included (ANSI/AAMI ST79, as taught by HSPA).
Safety numbers
- Eyewash: delivers tepid flushing fluid for 15 minutes at no less than 1.5 liters per minute (OSHA, citing ANSI Z358.1); ANSI Z358.1 places the station within 10 seconds of the hazard.
- Hand hygiene: an alcohol-based hand rub takes about 20 seconds (CDC).
Want to know how these fit into the exam? See what's on the CRCST and how long to study.
CRCST FAQ
What temperature is used for steam sterilization?
CDC's examples use 121°C (250°F) for gravity cycles and 132°C (270°F) for gravity or dynamic-air-removal cycles. Exposure times depend on the cycle and the load.
How often is a Bowie-Dick test done?
Daily, in an empty dynamic-air-removal (prevacuum) sterilizer, according to CDC.
How often should biological indicators be used?
At least weekly according to CDC, and with every load containing implants.
What temperature and humidity should sterile storage be?
ASHRAE Standard 170 (2024 addendum) sets sterile storage at 75°F (24°C) maximum and 60% relative humidity maximum, under positive pressure with at least 4 air changes per hour.
How long is ethylene oxide aeration?
CDC's example for PVC tubing is 12 hours at 50°C or 8 hours at 60°C.
Free CRCST practice questions
More CRCST guides
- CDC: Steam sterilization cycle times (Table 7)
- CDC: Flash steam sterilization parameters (Table 8)
- CDC: Sterilizing practices
- CDC: Disinfection and sterilization summary recommendations
- CDC: Ethylene oxide sterilization
- ANSI/ASHRAE/ASHE Standard 170-2021, Addendum o (2024)
- CDC: A rational approach to disinfection and sterilization
- OSHA 29 CFR 1910.1047: Ethylene oxide
- OSHA: Best practices guide, eyewash (citing ANSI Z358.1)
- NIH Technical Bulletin: emergency showers and eyewash (ANSI Z358.1)
- CDC: Clinical safety, hand hygiene for healthcare workers
- HSPA: Fundamentals of sterile storage
- HSPA/IAHCSMM self-study lesson CRCST 173 (set weight)
- HSPA self-study lesson CRCST 185 (chemical indicator types)
- HSPA 2026 Certification Handbook