Spare Parts
& Critical Component List FAQ

A critical component list exists to ensure that when a GxP-critical part fails, it gets replaced with a specifically pre-identified, qualified part — not whatever similar-looking item happens to be available — so the equipment's validated state is preserved rather than accidentally changed during an urgent repair.

Without this list, an emergency repair under time pressure is exactly when an unqualified substitute part is most likely to get installed, since the person doing the repair is focused on getting the equipment running again, not on whether the replacement part matches what was originally qualified.

A part should be classified as critical if its failure or an incorrect substitution could affect a GxP-critical function, product quality, or data integrity, while routine consumables — items with no meaningful performance variation between suppliers, such as generic fasteners or standard filters with no product-contact or functional criticality — don't need to be tracked with the same rigor.

Engineering, working from the equipment's risk assessment and original design documentation, should propose the critical component classification, with QA reviewing and approving the final list, since the classification directly determines how tightly future replacements will be controlled.

Yes — embedded firmware and control software should be tracked as critical components where they affect a GxP-critical function, since a firmware update or replacement can change equipment behaviour just as significantly as a physical part swap, and it needs the same level of version control and change assessment before being applied.

A bill of materials is a comprehensive list of every part that makes up a piece of equipment, generated primarily for manufacturing and assembly purposes, while a critical component list is a focused subset identifying only the parts whose replacement needs GxP-level control — a critical component list is derived from the bill of materials through a risk assessment, not a replacement for it.

A critical spare part should be qualified as an approved replacement before it's stocked, not after an emergency installation — stocking only pre-approved parts is what actually prevents an unqualified substitute from being installed under time pressure, since by the time a failure happens, there's no time left to properly assess a new, unvetted part.

No — substituting a critical component with a different manufacturer's part, even one marketed as equivalent, should go through change control, since "equivalent" is a claim that needs independent verification against the original part's relevant specifications before it's accepted as a like-for-like replacement.

Obsolescence should be identified proactively through periodic review of the critical component list against supplier availability, with a documented strategy — such as qualifying an alternative part, last-time-buy stocking, or planning equipment replacement — established before the part actually becomes unavailable and an emergency substitution becomes the only option.

Yes — a critical spare part with a defined shelf life or storage condition requirement, such as an electronic component sensitive to humidity or a seal material that degrades over time, needs to be stored and tracked accordingly, since installing an expired or improperly stored spare can introduce exactly the kind of performance risk the critical component list was meant to prevent.

The list should specify the exact part number and manufacturer for the currently qualified spare, with any approved alternative parts also explicitly listed by their own part numbers — a generic functional description alone, like "pressure sensor, 0 to 10 bar," doesn't tell a technician under time pressure which specific part is actually approved for use.

The situation should be treated as a deviation, with a documented risk assessment covering the equipment downtime impact and, if an emergency unqualified substitute is used to restore operation, a plan to qualify or replace that substitute with the correct approved part as soon as practical, plus an assessment of any GxP data generated while the substitute was in use.

Yes — an emergency substitution should be documented with the specific justification for deviating from the approved critical component list, an assessment of the substitute part's suitability, and a defined plan and timeline for reverting to the approved part, rather than being logged the same way as a routine, planned replacement using an already-qualified spare.

A component used across multiple equipment units should be documented once as a shared critical component with cross-references from each piece of equipment's own critical component list, rather than duplicated separately in each list, so that a supplier change, obsolescence issue, or qualification update only needs to be tracked and actioned in one place.

Yes — any equipment modification that adds, removes, or changes a critical component should trigger an update to the critical component list as part of the same change control record, since a list that isn't kept synchronized with the equipment's actual current configuration quickly becomes unreliable as a reference for future repairs.

A periodic physical inventory check, comparing what's actually on the shelf against the current approved critical component list, should be performed on a defined schedule, checking both that approved spares are genuinely in stock and that no unapproved or superseded parts have been mistakenly kept as usable inventory.

The maintenance or repair record itself is usually sufficient to document a spare part's installation, provided it specifically references the part number and lot or serial number installed and confirms it matches the approved critical component list — a separate standalone document isn't generally needed if the maintenance record captures this level of detail.

An inspection-ready critical component list should let a reviewer confirm exactly which parts are considered critical, their approved manufacturer and part number, any qualified alternatives, and the basis for their criticality classification.

• Equipment identifier and the specific component or sub-assembly.
• Criticality rationale linking the component to a GxP-critical function.
• Approved manufacturer and part number, plus any qualified alternatives.
• Storage or shelf-life requirements, where applicable.
• Revision history showing when and why the list was updated.

The critical component list and its full change history should be retained for at least as long as the equipment it supports remains in GxP use, since it's part of the evidence showing which specific parts were approved for use in the equipment throughout its operational life, including during past periods that may later come under regulatory scrutiny.

Inspectors typically pick a recent repair or maintenance record involving a critical component, trace the part actually installed back to the critical component list to confirm it was an approved part, and check whether any substitutions were properly documented and assessed rather than made informally.

A frequent finding is a maintenance record referencing a part by a generic description with no specific part number, making it impossible to confirm whether the installed component actually matches what the critical component list approves.

The most common mistake is letting the critical component list fall out of sync with reality — parts get substituted informally during urgent repairs without updating the documented list or going through change control, and over time the list stops reflecting what's actually installed in the equipment, undermining its entire purpose as a control.