Impact Assessment in Cleanrooms: How to Manage Change Control According to ISO 14644-5:2025 (Without Findings)

In cleanrooms, change is inevitable: new equipment, new materials, personnel changes, major maintenance activities, disinfectant changes, HVAC modifications, layout optimisations.

The problem is that, if changes are not properly managed, they become the number one cause of:

• deterioration of particle and/or microbiological trends
• loss of cleanroom class or environmental instability
• repeated deviations “without a clear root cause”
• audit findings (due to missing or weak impact assessments)

ISO 14644-5:2025 places a strong spotlight exactly here: Impact Assessment integrated into Change Control.

What is an Impact Assessment in a cleanroom (QA perspective)?

An Impact Assessment is a structured evaluation of the potential effects of a change on:

• particulate contamination (air and surfaces)
• microbiological contamination (where relevant, e.g. GMP environments)
• critical parameters (cleanroom class, ΔP, airflow patterns, temperature/humidity, etc.)

It is not an “extra” document. It is the element that makes change control defensible and audit-ready when the inspector asks:

“How did you assess that this change does not compromise the state of control?”

**The 9 technical factors to evaluate

(the “anti-gap” mental checklist)**

A robust Impact Assessment cannot stop at “no impact expected.” At a minimum, the following drivers should be considered (adapt them to your context):

1) Utilities

HVAC, gases, compressed air, water systems, etc.
Example impact: ductwork activities → release of particles, microorganisms or contaminants.

2) Vibrations

New equipment or operating modes may resuspend settled particles or disturb unidirectional airflow.

3) Electromagnetic fields

Potential interference with sensors, monitoring systems or alarms.

4) Electrostatic properties (ESD)

New materials or furniture may attract particles or generate discharges
(critical in microelectronics, but not limited to it).

5) Lighting

Changes in lighting/UV may affect materials, thermal load and convective flows.

6) Chemical emissions (AMC)

Outgassing or vapours from adhesives, plastics, lubricants.
A major topic in microelectronics, but also relevant in life sciences
(material compatibility, residues, odours, surface films).

7) Thermal load

Equipment generating heat or cooling can create air currents that disrupt airflow patterns.

8) Airflow patterns

Large objects or new layouts may create shadow zones, turbulence or recirculation.

9) Changes to operating procedures

Modifications to SOPs (gowning, cleaning, material transfer) may introduce human-factor risks and cross-contamination.

Practical process: writing an “audit-ready” Impact Assessment in 7 steps

Step 1 — Classify the change (GxP impact)

Key questions:

• does it impact the controlled environment?
• does it affect qualified parameters?
• does it impact product or patient?
• does it require QA and/or Validation approval?

Step 2 — Define the “before vs after” scenario

• what changes physically?
• what changes operationally?
• who is impacted?
• when and for how long?

Step 3 — Evaluate impact on contamination and state of control

Use a simple but traceable methodology (FMEA is often ideal):

• failure mode
• cause
• effect
• existing controls
• severity / probability / detectability
• residual risk

Step 4 — Define mitigations and additional controls

Typical mitigation examples:

• extraordinary cleaning
• temporary barriers / area confinement
• additional environmental monitoring (extra locations or higher frequency)
• targeted training
• operational constraints (limit personnel, stop production during critical phases)

Step 5 — Define qualification / requalification needs

If you impact:

• airflow patterns
• HEPA/ULPA filters
• pressure differentials
• critical layout elements

a partial or full requalification (even local) is often justified.

Step 6 — Controlled implementation (planned window)

Rule of thumb:
high-impact changes should be implemented outside production or under defined restrictions.

Step 7 — Post-implementation verification (effectiveness)

Closing the change “on paper” is not enough. Evidence is required that:

• trends do not worsen
• alarms do not increase
• defined controls are effective

Four typical examples (auditors love these)

Example A — Increase in number of operators

Impact: more particles, more movement, higher behavioural risk
Mitigation: limit occupancy time, additional EM during activities, retraining, optimise gowning/garments

Example B — Introduction of new equipment

Impact: vibrations, heat, airflow obstruction, machine-generated particles
Mitigation: particle testing with equipment running, repositioning, airflow guides, extra cleaning

Example C — Change of disinfectant

Impact: residues, material compatibility, contact time, operator safety, effectiveness on environmental flora
Mitigation: efficacy studies, SOP updates, training, rinse/residue management

Example D — HEPA filter replacement (extraordinary maintenance)

Impact: HVAC shutdown, loss of overpressure, debris release, particle re-dispersion at restart
Mitigation: area confinement, deep cleaning post-intervention, filter integrity testing, air flush, particle verification

Mandatory linkage: Impact Assessment ↔ OCP ↔ Change Control

“Inspector-grade” best practice:

• the OCP defines how cleanroom changes are managed
• Change Control includes a mandatory environmental impact assessment section
• after the change, the OCP is updated where required

This triangulation is what makes the system alive and effective, not bureaucratic.

Common mistakes that lead to findings

• urgent changes implemented without impact assessment
• impact assessed only on the process, not on the environment
• no post-change evidence (no intensified monitoring)
• OCP not updated after changes
• EM investigations that fail to link trend deterioration to recent changes

Do you want a complete Impact Assessment checklist
(with ready-to-use fields, technical factors, real examples and direct linkage to OCP/change control)?

👉 You’ll find it in the complete guide
“ISO 14644-5:2025 – Operational Guide to Cleanroom Operations” on guidegxp.com.