What goes into certifying a cleanroom — and why it matters for your patients

If you operate a sterile compounding pharmacy or a pharmaceutical manufacturing facility, you’ve heard the phrase “cleanroom certification.” But unless you’ve seen the process firsthand, it can feel like a black box — a technician shows up, runs some tests, hands over a report, and leaves.

That report represents a great deal more than a signature on paper. It’s the documented evidence that your controlled environment is performing the way the standards require — protecting your products, your staff, and ultimately your patients. Here’s what’s actually happening during a cleanroom certification visit, and why the rigor behind it matters.

What is a cleanroom, really?

A cleanroom is a controlled environment in which airborne particulate contamination is managed to a defined level. In pharmaceutical and compounding contexts, this typically means an ISO-classified space where the concentration of particles — and often viable microorganisms — is kept within strict limits.

The classification system most used in the U.S. and internationally is ISO 14644-1, which defines cleanliness levels from ISO Class 1 (the most stringent) down to ISO Class 9. Sterile compounding pharmacies operating under USP <797> and USP <800> are required to maintain ISO Class 5 conditions at the point of product preparation, typically inside a biological safety cabinet or laminar airflow workbench, with surrounding buffer and ante areas meeting ISO Class 7 or 8.

The key tests performed during certification

A thorough cleanroom certification is not a single measurement. It’s a battery of tests, each targeting a different performance characteristic of the HVAC and filtration system.

HEPA/ULPA filter integrity (leak testing)

Every HEPA or ULPA filter installed in the room is challenged with a polydisperse aerosol — typically generated by a Laskin nozzle — and scanned downstream with a photometer or particle counter. Any leak at the filter frame, seal, or media surface is identified and measured against the acceptance threshold defined in IEST-RP-CC034 and related standards.

Airflow velocity and uniformity

Airflow at the supply face must meet design specifications for both average velocity and uniformity. Low average velocity means reduced dilution and removal of airborne particles. Poor uniformity creates dead zones where contamination can accumulate. Measurements are taken on a defined grid — commonly 20 points or more — and evaluated against the facility’s design parameters or applicable standards such as CETA CAG-003.

Non-viable particle counting

An optical particle counter samples air at multiple locations and size fractions (typically ≥0.5 µm and ≥5.0 µm) to confirm the room’s ISO classification is being achieved under as-built, at-rest, and operational conditions. The number of sample locations, sample volumes, and acceptance criteria are all defined by ISO 14644-1.

Room pressurization and air changes per hour

For spaces handling hazardous drugs under USP <800>, negative pressure differentials between zones must be maintained and documented. For sterile compounding buffer rooms, positive pressure relative to the adjacent space is required. These differentials — along with air change rates — are measured and compared to design targets.

Temperature and relative humidity

Environmental parameters such as temperature and humidity are recorded to confirm they remain within ranges that support both product stability and personnel comfort during operations.

How often should cleanrooms be certified?

USP <797> requires that cleanrooms and primary engineering controls be certified at least every six months — and also after any event that could affect performance: a filter replacement, a significant HVAC repair, a facility renovation, or evidence of contamination. Some organizations choose quarterly certification cycles for higher-risk environments.

Certification frequency is ultimately a risk management decision. The question to ask is: what could have changed since the last report was issued, and would I know if it had?

What a trustworthy certification report should include

Not all certification reports are created equal. When evaluating a vendor or reviewing your own documentation, a complete and defensible report should contain:

• Full equipment inventory with calibration dates and expiration
• Raw data for all measured parameters — not just pass/fail summaries
• Grid maps showing spatial distribution of airflow and particle counts
• Clear identification of the applicable standard and acceptance criteria
• Technician credentials and signature
• Timestamps for each test, tied to facility conditions at time of testing
• Any corrective actions taken or recommended

Sparse reports that show only a single “PASS” column give you very little to work with during an FDA inspection or a state board review. Detailed data tells a story about the performance history of your environment — and gives your team the foundation to identify trends before they become failures.

The bottom line for compounding pharmacies

Cleanroom certification is a patient safety activity. The ISO Class 5 environment around your sterile preparations exists to protect every patient who receives a compounded product. When that environment is certified rigorously, documented thoroughly, and reviewed intelligently, your team has confidence that the controls are working. When it’s treated as a checkbox, the gap between your report and your actual risk profile quietly widens.

At LabCertTech, our certification process is built around transparent, data-rich documentation — because you deserve to know exactly what was measured, how, and what it means for your facility.