CQV & QMS Knowledge Booklet · Module 2
HVAC System Design
For Pharmaceutical Facilities
The mechanical system that delivers the conditions a classified room is specified to hold — air handling unit architecture, how much air and why, filtration, humidity control and the qualification that proves it.
- ISPE HVAC Good Practice Guide
- EudraLex Vol. 4 Annex 1
- EN 1822
- ISO 16890
- EN 1886
- NFPA 90A
Most HVAC disputes on a pharmaceutical project are not disputes about equipment. They are disputes about a number — the supply air volume — that was fixed early, by one requirement, and never re-tested against the other three.
This module sets out the system in airflow order and the calculations that govern it, then follows the qualification that has to prove the room holds what the specification promised, in the weather the design was supposed to survive.
What this module covers
- Origins
- How pharmaceutical HVAC diverged from comfort engineering, and the three dates at which a facility's documentation may have stopped being current.
- Standards map
- ISPE HVAC Good Practice Guide 2nd Edition, Annex 1, ASHRAE, EN 1822, ISO 16890, SMACNA, EN 1886, NFPA 90A, NEBB.
- AHU architecture
- Every section in airflow order and why it sits there — including why the terminal HEPA belongs at the room, not in the unit.
- Determining air quantity
- The central calculation: supply air is the greatest of four independent requirements, not one of them and not their sum.
- Pressurisation airflow
- How much excess supply air a differential actually needs — and why no system holds pressure across an open door.
- Fans and fan laws
- Why a 20 % speed reduction roughly halves fan power, and the case for a fan array in a facility that cannot lose its HVAC.
- Filtration staging
- The pre-, fine- and terminal-filter train, EN 1822 classification stated correctly, and ISO 16890 for general ventilation.
- Filter differential pressure
- Initial and changeout values by stage, and why calendar-based HEPA replacement breaks a leak-tested seal for no reason.
- Temperature & humidity
- Chilled water, brine and desiccant routes — and the single check that decides which one a specification actually needs.
- Ductwork
- Pressure class against fan shut-off, leakage testing before insulation, lining, and HEPA housings that can actually be scan-tested.
- Fire & life safety
- Where NFPA 90A and the pressure cascade pull against each other, and how that conflict is reconciled rather than ignored.
- Heat load
- Sensible, latent and Sensible Heat Ratio — and why process equipment, not occupancy, usually dominates in a pharmaceutical plant.
- Validation lifecycle
- DQ through PQ for HVAC, including why a PQ run only in mild weather has not tested the design.
- Testing frequencies
- Which standard governs which test, and what Annex 1 actually requires now that fixed intervals have gone.
Questions this module answers
- Was your supply air volume sized on air change rate alone, or against all four governing requirements?
- Can the chilled water you actually have deliver the room humidity your URS specifies?
- Is your terminal HEPA housing fitted with an aerosol injection port and scan clearance?
- Does your heat load calculation include fan gain, and the equipment added since it was written?
Also in this series
All modules