Sterilizer Requalification After Change: A Risk-Based Change-Control Framework

A sterilizer should not be requalified simply because a calendar date has arrived, nor should every service visit automatically trigger the same testing package. The more useful question is whether a change or event has altered the evidence supporting the facility’s validated process.

This article addresses the change-control decision that follows an event. It is not a maintenance or repair work instruction, and it is not a detailed framework for evaluating a changed steam-sterilizer load or packaging configuration. Those topics require their own procedures and supporting evidence. This article instead explains how to classify an event, define its potential process impact, and select an appropriate documented response.

The terms verification, requalification, and investigation are used here as facility-quality-system terminology. CDC guidance describes specific sterilizer-testing and monitoring recommendations, but it does not establish universal definitions for these three terms. Their exact meaning, decision thresholds, and required evidence should come from the facility’s approved procedures, equipment instructions, and applicable requirements.

When should a requalification review be considered?

CDC identifies installation, relocation, redesign, major repair, and sterilization failure as circumstances in which testing should occur before a sterilizer is returned to routine use. It also describes additional testing when major changes are made to packaging, wraps, or load configuration [1]. These recommendations are starting points for assessing the event; the final scope should reflect the sterilization modality, affected process, and facility procedure.

Other events may be risk-assessment triggers rather than automatic requalification requirements. Examples can include a utility change, work on a process-critical component, a control-system intervention, or a recurring abnormal result. The relevant question is whether the event could affect a critical process function or the accuracy of process measurements. Depending on the assessment, the appropriate response may be documented verification, focused requalification, a broader investigation, or a combination of activities. These categories are facility-defined terms, not universal CDC classifications.

How this framework differs from maintenance and load-change guidance

A maintenance or repair article typically explains how to document the work performed and what checks may be required before equipment returns to service. A load-change article typically focuses on the affected packaging, product, or load configuration and the evidence needed for that change. This framework begins after or alongside those activities and asks a different question: what level of quality-system response is justified by the event and its potential effect on the validated process?

Accordingly, this article does not prescribe a maintenance checklist, a universal post-repair test package, or one standard evaluation for every steam load change. The assessment should use the facility’s approved procedures and the equipment manufacturer’s instructions.

A decision process based on the event

1. Classify what happened

Document whether the event involved installation, relocation, redesign, repair, software or control changes, packaging or load changes, a failed indicator, an abnormal cycle record, or another deviation. Record when it occurred, which equipment and cycle types may be involved, and whether processing continued afterward.

Classification helps separate different quality activities. A defined maintenance task may require confirmation that the affected function operates as intended. A chamber or process-control change may justify a broader reassessment. A positive biological indicator or other sterilization failure is primarily an investigation trigger; it should not be treated as evidence that a predetermined requalification package alone will resolve the event.

2. Assess possible process impact

Identify the process function that could have changed. Depending on the modality, this may include sterilant delivery, air removal, temperature or pressure control, exposure conditions, load support, packaging performance, or measurement and recording accuracy.

Do not assign an automatic test package solely because work involved steam, electricity, drainage, ventilation, sensors, valves, vacuum equipment, chamber assemblies, or controls. Instead, determine whether the work could influence the validated process and follow the manufacturer’s instructions and the site’s approved change-control procedure. This assessment is the basis for deciding whether the facility’s defined verification, requalification, investigation, or combination of activities is appropriate.

3. Define the affected scope

Identify the specific cycle types, load families, packaging systems, and products that may be affected. Evidence from one cycle or configuration should not automatically be treated as evidence for every modality, cycle, load, or product. The scope should correspond to the change and the facility’s validated process.

For a packaging or load-configuration change, CDC recommends biological and chemical indicator testing of representative products. Items should remain quarantined until the results support release [1]. The facility’s procedure should define the representative configuration and the extent of the evaluation. This article does not establish one universal load arrangement.

4. Select evidence from approved procedures

Testing should be selected from the applicable procedure and equipment instructions rather than from a generic checklist. Depending on the event and modality, the evidence may include review of physical records, chemical or biological indicators, air-removal testing where applicable, distribution studies, product-specific assessment, or other approved verification activities.

CDC specifically identifies air-removal testing for dynamic-air-removal steam sterilizers within its sterilizer-testing recommendations [1]. For a positive biological indicator in a steam sterilizer, CDC describes taking the sterilizer out of service, reviewing operator practices and cycle selection, evaluating the indicator and control, involving maintenance personnel, and repeating biological-indicator testing in consecutive cycles. Continued positive results require escalation and may require recall and reprocessing of affected supplies [3].

Important limitation: the three-consecutive-cycle approach described by CDC is a protocol for managing a positive biological indicator in a steam sterilizer. It is not a universal requalification rule and should not be applied automatically to every sterilizer modality, maintenance event, change, or investigation.

Maintenance records and evidence before return to service

Maintenance documentation should identify the work performed, the reason for the intervention, the affected functions, and any post-maintenance checks required by the manufacturer or facility procedure. CDC recommends that preventive maintenance be performed by qualified personnel according to the manufacturer’s instructions and that records be retained as part of the quality-control program [2].

When an event could affect displayed or recorded process parameters, the assessment should address measurement accuracy. The record should state whether calibration or functional verification was required and link the result to the decision made. The specific method, acceptance criteria, and timing must come from the applicable procedure or manufacturer instructions.

Before return to service, an authorized reviewer should confirm that the defined assessment is complete, deviations have been addressed, and the available evidence supports the affected scope. If the evidence does not support release, the equipment or affected work should remain on hold while the investigation continues. Review of the first routine cycles may provide useful follow-up, but it does not replace procedure-specific testing required before release.

What the decision record should contain

A concise record should allow an independent reviewer to understand both the event and the rationale. It should include:

• Equipment identification, location, modality, and affected cycle types.
• Description and date of the change, repair, failure, or deviation.
• Impact assessment and defined affected scope.
• Relevant maintenance, calibration, and service documentation.
• Load, packaging, or product information used in the assessment.
• Tests performed, procedures followed, results, and deviations.
• Disposition of held, recalled, or reprocessed items when applicable.
• Corrective actions, approvals, and authorization for return to service.

These records supplement cycle-by-cycle documentation. CDC recommends recording the sterilizer and cycle, load identification, contents, exposure parameters, operator, and mechanical, chemical, and biological monitoring results for each cycle [2].

Practical takeaway

Use requalification as one possible outcome of a documented change-control assessment, not as a synonym for every verification or investigation activity. Installation, relocation, redesign, major repair, sterilization failure, and major packaging or load changes are recognized reasons to consider testing before routine use [1]. Utility changes, maintenance interventions, calibration concerns, and adverse trends should be evaluated for process impact rather than assigned an automatic test package.

The final decision should be modality-specific, procedure-specific, and supported by documented evidence. When existing evidence no longer clearly represents the current process, place affected work on hold, define the appropriate assessment, involve qualified personnel, and document the basis for return to service.

Educational disclaimer: This article is for professional education and does not replace applicable regulations, standards, validated procedures, manufacturer instructions, or site-specific quality-system requirements.

References

1. Sterilizing Practices. Centers for Disease Control and Prevention. 2023-11-28.
2. Recommendations for Disinfection and Sterilization in Healthcare Facilities. Centers for Disease Control and Prevention. 2023-12-20.
3. Table 12: Suggested protocol for management of positive biological indicator in a steam sterilizer. Centers for Disease Control and Prevention. 2023-12-20.
4. Improving Pressure Steam Sterilization Quality Through Healthcare Failure Mode and Effects Analysis: A Pre-Post Intervention Study in Central Sterile Supply Departments. PubMed. 2025.

Educational overview. Follow the applicable product instructions, validated procedures, local regulations and your facility’s approved policies.