1.0 Purpose

To describe the procedure for performing the Bowie-Dick test to assess steam penetration and air removal efficiency in steam sterilizers (autoclaves).

2.0 Scope

This SOP applies to all steam sterilizers (autoclaves) used in pharmaceutical manufacturing, microbiology laboratories, and other controlled areas requiring sterilization of equipment and materials.

3.0 Responsibility

• Engineering Department: To perform the test, maintain records, and ensure equipment functionality.
• QA Department: To review and approve test results.
• Production/Microbiology: To support test scheduling and compliance.

4.0 Definitions

• Bowie-Dick Test: A diagnostic test that detects the presence of residual air, inadequate steam penetration, or air leaks in pre-vacuum steam sterilizers.
• Test Pack: A commercially prepared or standard folded towel pack containing a Bowie-Dick indicator sheet.

5.0 Materials and Equipment

• Commercially available Bowie-Dick test pack (or equivalent validated pack)
• Pre-vacuum steam sterilizer (autoclave)
• Cycle printout/chart recorder (time, temperature, pressure)
• Logbook for recording results

6.0 Procedure

6.1 Preparation

1. Ensure the sterilizer chamber is empty.
2. Preheat the sterilizer according to the manufacturer’s instructions.
3. Place the Bowie-Dick test pack horizontally in the front, bottom shelf, near the drain line (most challenging location for steam penetration).

6.2 Test Cycle

1. Set the sterilizer to run a Bowie-Dick test cycle:
   • Temperature: 134 ± 1 °C
   • Exposure time: 3.5 minutes
   • Vacuum sequence: As per sterilizer design (pre-vacuum cycles)
2. Start the cycle and allow it to complete.

6.3 Interpretation of Results

1. After the cycle, remove the test pack and open immediately.
2. Examine the indicator sheet for uniform color change.
   • Acceptable Result: Uniform color change over the entire sheet, indicating proper air removal and steam penetration.
   • Fail/Reject Result: Non-uniform color change (e.g., lighter areas, streaks, or uneven spots), indicating air entrapment or inadequate steam penetration.

6.4 Frequency

• Perform the Bowie-Dick test daily before routine sterilization loads.
• Perform after any major maintenance or relocation of the sterilizer.

7.0 Precautions

• Do not use the sterilizer for routine loads if the Bowie-Dick test fails.
• Investigate and correct root cause before resuming sterilization.
• Always use validated test packs within expiry date.

8.0 Documentation

• Record date, sterilizer ID, cycle parameters, and test results in the Bowie-Dick Test Logbook.
• Attach the used indicator sheet to the record for traceability.
• Document any deviations or failures with corrective and preventive actions (CAPA).

9.0 References

• ISO 11140-4: Sterilization of health care products — Chemical indicators — Part 4: Class 2 indicators for Bowie-Dick type air removal test sheets and packs
• EN 285: Sterilization — Steam sterilizers — Large sterilizers
• PDA Technical Report No. 1: Validation of moist heat sterilization processes

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