Cell and gene therapy cleanroom design: grades, segregation and flows

By ZY Cleanroom · Updated 2026-11-01 · Sources at the end of the page

Grade by process step

Part IV section 9.5 sets the grade by whether the product is exposed.

Limits by grade

Part IV para 4.39 gives particles of 0.5 µm and larger per m³, with the ISO class at rest and in operation.

Segregation and multi-product use

A multi-product facility is acceptable with risk measures against mix-ups and cross-contamination (para 4.13). Activities with infectious viral vectors, for example oncolytic viruses, take place in a segregated area (para 4.16).

Two different ATMPs or batches in one area at the same time are not acceptable, except in closed systems with added measures (paras 4.18 and 4.19). Two isolators processing different viral vectors in one room need 100% exhaust with no recirculation (para 4.20). Replication-competent vectors may not share an incubator with other materials (para 4.24).

UK HTM 03-01 Table 6 describes a gene therapy clean room as a pharmacy clean room plus a negative-pressure access lobby and controlled exhaust.

Air, airlocks and flows

Clean areas are entered through an airlock with interlocked doors or procedural controls, and the final stage matches the room's grade at rest (para 4.35). Changing rooms act as airlocks (para 4.36). False ceilings are sealed (para 4.33).

Air handling units must prevent cross-contamination and may be specific to an area. Consider single-pass air where the product risk requires it (para 4.30).

Lay rooms out in the order of the process (para 4.27), and separate flows of sterilised and non-sterile or used materials (para 4.28). Move materials in through double-ended sterilisers or hydrogen peroxide locks (para 9.50).

Pressure, air changes and climate

Part IV para 4.62 gives 10 to 15 Pa (guidance) between adjacent rooms of different grades, with cascades clearly defined and continuously monitored. Para 4.63 allows negative pressure for containment, for example with replication-competent vectors, if the negative area is surrounded by a positive clean area of suitable grade.

For a hospital pharmacy suite, HTM 03-01 Table 6 gives at least 20 air changes per hour, +10 Pa between classified rooms, 20 to 24 °C and up to 60% RH. Part IV sets no air change rate. Set your own values from your risk assessment.

The rules are being revised

Part IV was adopted on 22 November 2017 and has been operational since 22 May 2018. In 2025 the EMA inspectors' group agreed a concept paper to revise it in line with Annex 1, covering contamination control, barrier technology and closed systems. Check the current text before you fix the design.

Rules for US, Chinese and other markets are set by the regulator that will license the product. Check them separately.

Who approves the room

The regulator that licenses the product judges the facility, not the contractor. The contractor builds to your room data sheet and supplies test data. To have a room list reviewed, send it to ZY Cleanroom, a cleanroom design-and-build contractor with its own panel factory in Tianjin, China.

Related guides

• Cleanroom validation and handover: tests, IQ/OQ/PQ and documents
• Aseptic filling suite layout: grade A and B rooms and flows
• USP <797> compounding cleanroom for hospital pharmacy
• Contamination control strategy: what the building and air must provide
• Turnkey cleanroom contractor
• Room list builder

Sources

• European Commission, Guidelines on Good Manufacturing Practice specific to Advanced Therapy Medicinal Products, Part IV of EudraLex Volume 4 (adopted 22 November 2017; checked 31 October 2026)
• EMA, Concept paper on the revision of Part IV Guidelines on Good Manufacturing Practice specific to Advanced Therapy Medicinal Products (EMA/INS/GMP/48771/2025; agreed 15 April 2025; consultation 8 May to 8 July 2025; checked 31 October 2026)
• European Commission, EudraLex Volume 4 page (lists Annex 1 as fully applicable since 25 August 2024 and Part IV as operational as of 22 May 2018; checked 31 October 2026)
• EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (published 25 August 2022; applied from 25 August 2023, and from 25 August 2024 for point 8.123; checked 31 October 2026)
• NHS England, Health Technical Memorandum 03-01, Specialised ventilation for healthcare premises, Part A (published 22 June 2021; checked 31 October 2026)