Understanding the Bowie-Dick Test in Small Sterilizers:

What is the Bowie-Dick Test?

The Bowie-Dick test (BD-Test) is a type test originally defined for large sterilizers in standard EN 285, using a 7kg cotton pack with an indicator page as described in EN ISO 11140-3. This functional test ensures air removal and steam penetration effectiveness in steam sterilizers. While originally designed for large hospital autoclaves, the principles have been adapted for small sterilizers used in dental offices, clinics, and smaller healthcare facilities through specialized BD-Test programs.

Why Small Sterilizers Need Special Attention

Table-top sterilizers cannot use the original BD-cotton pack due to size constraints and different design requirements outlined in standard EN 13060. Unlike large sterilizers with extensive connection pipes between steam generators and chambers, table-top units have more compact designs that present unique challenges for steam distribution and air removal.

For Class B table-top sterilizers, alternative tests are available within BD-Test programs, including the Helix-Test according to EN ISO 11140-6 (former EN 867-5) and batch monitoring systems adapted to load difficulty per DIN 58921. These alternatives ensure proper functionality while accommodating the specific characteristics of smaller sterilization units.

How to Perform the Bowie-Dick Test

The Bowie-Dick test uses a specially designed test pack containing temperature-sensitive chemical indicators arranged in a specific pattern. For small sterilizers, the procedure involves:

• Placement: Position the Test Systems in the most challenging location within the chamber, typically the front bottom area near the door.
• Cycle Selection: Run a standard sterilization cycle according to the manufacturer's specifications, usually at 134°C (273°F) for 3.5 minutes or equivalent parameters.
• Result Interpretation: After the cycle, examine the indicator pattern. A uniform color change across all indicators indicates proper steam penetration. Any areas showing incomplete color change suggest inadequate steam contact.

Testing Frequency and Standards Compliance

According to EN ISO 17665, steam penetration testing must be performed before daily startup to ensure air removal from the steam generator, sterilizer chamber, and connecting pipes. For table-top sterilizers, this daily functional test uses either the Helix-Test (EN ISO 11140-6) or adapted batch monitoring systems that meet the requirements outlined in relevant standards.

However, it's important to note that morning type tests only verify sterilizer functionality after startup. They don't automatically guarantee that all subsequent sterilization batches will produce sterile goods, particularly for challenging loads like hollow devices, minimal-invasive surgical instruments, and dental handpieces where even small amounts of non-condensable gases (NCG) can be critical.

Beyond Daily Testing: Batch Monitoring

While daily BD-Tests verify sterilizer functionality, batch monitoring systems are essential for ensuring load-specific sterilization effectiveness. These systems must represent the actual requirements of the load being processed rather than just sterilizer function.

Two approaches for selecting appropriate batch monitoring include using tests whose requirements have been compared with defined loads according to DIN 58921 ("Medical Device Simulator") or employing test systems with varying difficulty levels on a trial basis. The goal is to select the test with the highest requirements that still provides satisfactory results, ensuring adequate challenge for the specific load types being processed.

This article serves as an educational resource for healthcare professionals seeking to understand and implement proper Bowie-Dick testing procedures in small sterilizer environments. For specific regulatory requirements and detailed procedural guidelines, consult your local health department and sterilizer manufacturer recommendations.