How a subtle failure pattern can become a serious sterilization risk
The morning Bowie-Dick test looked almost normal.
Most of the indicator had changed color as expected. Only a faint, lighter area remained near the center of the sheet. It was small enough that the technician believed the result was acceptable.
The test was documented as a pass, and the sterilizer was released for use.
Over the following weeks, the same faint pattern appeared several more times. Because the result was not dramatically different from a passing test, the variation became familiar. What should have prompted investigation gradually became accepted as normal.
Then the pattern worsened.
A supervisor reviewing the daily records noticed that the indicator sheets were not showing a completely uniform response. The sterilizer was removed from service, and Facilities and service personnel were contacted.
The investigation identified an air-removal problem that had been developing over time.
The failure mode is real: a Bowie-Dick result can appear nearly acceptable while still indicating residual air, inadequate steam penetration, non-condensable gases, or another problem affecting the sterilization process.
“A Bowie-Dick test should never be treated as a simple color check. Even a subtle, nonuniform pattern can be an early warning that air removal, steam quality, or another part of the sterilization system needs attention. Recognizing that warning—and investigating it before it becomes a larger problem—protects patients, instruments, and the entire surgical schedule.” — Len Sparks, Chief Operating Officer, VERDA Water Quality Systems
A Bowie-Dick test is not graded on a curve
A Bowie-Dick test evaluates whether a dynamic-air-removal sterilizer can remove air and permit steam to penetrate a standardized challenge device.
The result must be interpreted according to the test manufacturer’s instructions. A lighter area, incomplete color development, uneven pattern, or other abnormality may indicate that air remained in the test pack.
“Almost uniform” is not necessarily a pass.
Residual air matters because steam must contact the surfaces being sterilized. Air pockets can act as barriers, preventing saturated steam from reaching part of a porous load.
The risk of a false pass
When a failed test is incorrectly accepted, the concern extends beyond the indicator sheet.
The facility may need to determine:
- How long the condition may have existed
- Which loads were processed in the affected sterilizer
- Whether cycle records showed additional warning signs
- Whether previously processed items require assessment or recall
- Whether the problem originated in the sterilizer or supporting utilities
Possible causes include a leaking door gasket, deteriorating vacuum performance, malfunctioning valves, restricted drainage, steam-supply instability, or non-condensable gases.
The longer an abnormal pattern is accepted, the more complex the investigation can become.
Familiarity can normalize an abnormal result
One of the greatest risks in daily testing is not a lack of effort. It is the gradual normalization of variation.
When a questionable pattern appears repeatedly without an obvious adverse event, staff may begin to see it as characteristic of the machine, the test pack, or the morning cycle.
That is why interpretation cannot depend on memory or visual familiarity alone.
A strong process includes:
- Current interpretation guidance at the point of use
- Training on acceptable and unacceptable patterns
- Escalation of questionable results
- Review by a supervisor or another qualified individual
- Retention of test records for trending
- Correlation with mechanical cycle data
- The pattern should never be accepted simply because it appeared yesterday.
Troubleshooting beyond the sterilizer
A failed Bowie-Dick test does not automatically mean that one sterilizer component has failed.
The root cause may involve the sterilizer, steam distribution system, vacuum utilities, cooling water, boiler operation, piping, condensate removal, or non-condensable gases.
That is why effective troubleshooting requires coordination among Sterile Processing, Facilities, service personnel, and water and steam-quality experts.
VERDA approaches these events as system-level problems. Rather than looking only at the test sheet or replacing components one at a time, the goal is to understand how water, steam, equipment, utilities, and operating procedures interact.
A subtle failure pattern can be easy to dismiss. It can also be the earliest warning that something upstream is changing.
The lesson is simple: a Bowie-Dick test should not merely change color. It should meet the test manufacturer’s acceptance criteria completely and consistently.