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newSchoolWorks.com › VoTechWorks › Health & Personal Services › Sterile Processing Technician › Sterilization Methods for Sterile Processing › Lesson 2
HLT-STER66-04 · Lesson 2 · 18 clock hours · lab

Steam Sterilization: Parameters, Cycles, Equipment Operation, and Loading

Objective. Students will correctly load, program, operate, and unload a gravity-displacement and a prevacuum steam sterilizer, verifying that all critical parameters (time, temperature, pressure, steam quality) were met before releasing a load.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Steam Sterilization: Parameters, Cycles, Equipment Operation, and Loading

Steam sterilization—also called autoclaving—is the most widely used method of sterilization in healthcare facilities. It uses saturated steam under pressure to kill all microbial life, including bacterial spores. As a Sterile Processing Technician (SPT), you must understand the critical parameters that make a steam cycle effective, recognize the two main cycle types, and load sterilizers correctly every time. Patient safety depends on it.

Why Steam Sterilization Works

Steam kills microorganisms through moist heat. When pressurized saturated steam contacts an instrument surface, it condenses and releases a large amount of energy, denaturing microbial proteins and destroying cell structures. Four parameters must work together for sterilization to succeed:

If any one of these four parameters is not met, the load cannot be released as sterile.

Gravity-Displacement Cycles

In a gravity-displacement sterilizer, steam enters at the top of the chamber. Because steam is lighter than air, it gradually pushes air downward and out through a drain at the bottom. Air removal is slow and incomplete compared with prevacuum cycles, which is why gravity cycles require longer exposure times.

Typical gravity-displacement parameters (always verify against manufacturer IFU and facility policy):

Gravity cycles are suitable for many items but are not appropriate for porous loads or items with lumens unless validated.

Prevacuum Cycles

A prevacuum (also called pre-vac or dynamic air removal) sterilizer uses a vacuum pump to pull air out of the chamber in one or more pulses before steam is admitted. Because air is actively removed, steam penetrates porous materials and complex instrument loads much more rapidly and reliably.

Typical prevacuum parameters:

Prevacuum cycles are the standard for most wrapped instrument sets, peel pouches, and porous goods in modern facilities.

Equipment and Controls

Before operating any sterilizer, review the manufacturer IFU for that specific model. Key components you will identify on the sterilizer diagram:

At the start of each day, a Bowie-Dick test (air removal test) must be run in prevacuum sterilizers before processing any loads. This test confirms that the vacuum system removes air effectively. Never skip this test.

Loading Principles

Incorrect loading is one of the most common causes of sterilization failure. Follow these HSPA-recommended principles:

Cycle Monitoring and Printout Interpretation

After every cycle, retrieve the printout immediately. Verify:

1. The temperature reached the required level and held for the full exposure time.

2. Pressure readings are consistent with the cycle type.

3. The cycle completed without fault codes.

4. Printout is signed, dated, and filed per facility policy.

If any parameter was not met, do not release the load. Quarantine the items, document the deviation, notify your supervisor, and reprocess according to facility protocol.

Wet Pack Recognition and Response

A wet pack—visible moisture on packaging or inside containers after sterilization—must never be released. Moisture compromises package integrity and the sterile barrier. Common causes include overloading, poor steam quality, or incorrect load configuration. Report wet packs immediately, repackage, and reprocess.

Safety Reminders

Key terms10

Saturated steamSteam that contains the maximum amount of water vapor at a given pressure and temperature, neither wet nor superheated; required for effective steam sterilization.
Gravity-displacement cycleA steam sterilization cycle in which steam entering the top of the chamber pushes air out through the bottom drain by gravity; uses longer exposure times than prevacuum cycles.
Prevacuum cycleA steam sterilization cycle that uses a vacuum pump to actively remove air from the chamber before admitting steam, allowing faster and more reliable penetration of porous and complex loads.
Critical parametersThe four factors that must all be met for steam sterilization to succeed: time, temperature, pressure, and steam quality.
Bowie-Dick testAn air-removal test run in a prevacuum sterilizer at the start of each day before any loads are processed, used to confirm that the vacuum system adequately removes air from the chamber.
Wet packA sterilized package or container that has visible moisture after the cycle; wet packs must not be released as sterile because moisture compromises the sterile barrier.
Class 1 chemical indicator (CI)A process indicator, such as sterilization tape, placed on the outside of a package to show that the package has been exposed to a sterilization process; does not confirm that sterilization was achieved.
Cycle printout (recorder chart)The paper record produced by the sterilizer showing time, temperature, and pressure readings throughout the cycle; reviewed after every run and kept as a permanent record.
Instructions for Use (IFU)Written directions from a device or equipment manufacturer specifying how a product must be prepared, processed, or sterilized; must be followed to ensure safety and effectiveness.
Wicking towelAn absorbent towel placed beneath metal instruments in a perforated tray to absorb condensate during sterilization and help prevent wet packs.

Worked examples4

1. Your gravity-displacement sterilizer printout shows a peak temperature of 250°F (121°C). The IFU for the wrapped instrument set requires a minimum hold time of 30 minutes at 250°F. The printout shows the temperature stayed at or above 250°F for 28 minutes before dropping during the exhaust phase. Can you release this load?
  1. Step 1: Identify the required parameter — the IFU specifies a minimum of 30 minutes at 250°F (121°C).
  2. Step 2: Read the printout — the temperature held at or above 250°F for only 28 minutes.
  3. Step 3: Compare actual vs. required — 28 minutes is less than the required 30 minutes; the hold time parameter was NOT met.
  4. Step 4: Apply the release rule — if any critical parameter is not met, the load must NOT be released.
Answer: No. The load must be quarantined. The hold time was 2 minutes short of the IFU minimum. Document the deviation, notify your supervisor, repackage items if packaging integrity is in question, and reprocess.
2. You retrieve a prevacuum cycle printout. The required parameters are 270°F (132°C) for 4 minutes. The printout shows: peak temperature 270°F, hold time 4 minutes 12 seconds, pressure consistent throughout, no fault codes. Are all critical parameters met?
  1. Step 1: Check temperature — printout shows 270°F; meets the requirement.
  2. Step 2: Check hold time — 4 minutes 12 seconds is greater than the required 4 minutes; meets the requirement.
  3. Step 3: Check pressure — described as consistent throughout, indicating no anomalies.
  4. Step 4: Check for fault codes — none present.
  5. Step 5: Confirm steam quality indirectly — a fault-free cycle with correct pressure and temperature suggests no steam quality alarms were triggered.
  6. Step 6: All four critical parameters are accounted for and met.
Answer: Yes. All critical parameters were met. Sign and date the printout, complete the cycle log, and the load may be released following inspection of each package for integrity.
3. After unloading a prevacuum sterilizer, you notice that three peel pouches feel damp and one stainless steel tray has water droplets visible on the wicking towel visible through the transparent side. What do you do, and how many items are affected?
  1. Step 1: Identify the problem — visible moisture on packages after a completed cycle meets the definition of a wet pack.
  2. Step 2: Count affected items — 3 damp peel pouches plus 1 wet instrument tray = 4 items are wet packs.
  3. Step 3: Quarantine all four items immediately; do not release them as sterile.
  4. Step 4: Inspect the remaining packages in the load for moisture before deciding on their status.
  5. Step 5: Document the wet pack event on the cycle log and notify your supervisor.
  6. Step 6: Investigate the probable cause (e.g., overloading, incorrect load configuration, steam quality issue) before reprocessing.
Answer: Four items are wet packs. All must be quarantined, repackaged, and reprocessed after the cause is identified. The load must not be distributed to clinical areas.
4. A facility policy states that wrapped instrument trays processed in a gravity-displacement sterilizer at 250°F require a 30-minute exposure. Your sterilizer timer shows the cycle ran, but the printout shows the temperature reached only 245°F before starting the exhaust phase. The sterilizer did not generate a fault code. What is your next action?
  1. Step 1: Recognize the deviation — 245°F is below the required 250°F; the temperature parameter was NOT met.
  2. Step 2: Note that the absence of a fault code does not mean sterilization was achieved; parameters must be confirmed on the printout.
  3. Step 3: Do not release the load — quarantine all items from this cycle.
  4. Step 4: Document the deviation on the cycle log with the exact temperature reading noted.
  5. Step 5: Notify your supervisor and the Biomedical/Facilities team so the sterilizer can be inspected before further use.
  6. Step 6: Repackage and reprocess items in a verified, functioning sterilizer.
Answer: Quarantine the load immediately. The temperature parameter was not met regardless of the absence of a fault code. Document, notify your supervisor, and have the sterilizer serviced before using it again.
In class: Instructor-led demonstration of the prevacuum sterilizer control panel, cycle programming, and load configuration using standard metal instrument trays and peel pouches; students observe and annotate a printed sterilizer diagram identifying chamber, drain, vacuum pump, steam inlet, and recorder chart. · Hands-on paired practice: each student pair loads a mixed tray (metal instruments in a perforated tray with a wicking towel, plus several peel pouches) following HSPA loading guidelines, runs a full prevacuum cycle, retrieves the printout, and records time, temperature, and pressure readings on a cycle log sheet. · Gravity-displacement cycle practice using a wrapped textile pack and a hard-case container; students compare printout parameters against manufacturer IFU minimum requirements and flag any deviation, then report findings in a written cycle evaluation form.
Materials: Prevacuum and gravity steam sterilizers, stainless steel instrument trays, perforated tray inserts, wicking towels, peel pouches and sealer, hard-case sterilization containers, sterilization tape (Class 1 CI), HSPA Central Service Technical Manual, manufacturer IFU for equipment and containers, cycle log forms
Check: Instructor uses a 20-point skills checklist observing each student independently load and operate a prevacuum cycle, interpret the printout, and complete the cycle log; pass mark is 16/20 with no critical errors (critical errors: incorrect temperature selected, load released without verifying all parameters, wet pack not reported); any critical error requires immediate remediation and recheck.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Sterilization
1. Which four critical parameters must all be verified on a steam sterilization cycle printout before a load is released as sterile?
Sterilization
2. What is the primary purpose of the Bowie-Dick test performed in a prevacuum sterilizer at the start of each day?
Sterilization
3. A sterile processing technician discovers visible moisture inside a wrapped instrument set after unloading a completed prevacuum cycle. What is the correct immediate action?
Sterilization
4. When loading peel pouches into a prevacuum sterilizer, which position best allows steam to circulate around the pouch contents?
Sterilization
5. A gravity-displacement sterilizer printout shows the temperature held at 250°F for 27 minutes. The IFU for the wrapped pack requires a minimum of 30 minutes at 250°F. Which statement is correct?
Sterilization
6. Which component of a steam sterilizer is located at the bottom of the chamber and allows air and condensate to exit during a gravity-displacement cycle?
Sterilization
7. A Class 1 chemical indicator (sterilization tape) that has changed color after a sterilization cycle tells the technician which of the following?
Sterilization
8. During a prevacuum sterilization cycle, why is a wicking towel placed beneath metal instruments in a perforated tray?
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