Pharma Cleanroom HVAC Upgrade: A Brief for Expansion Projects

A pharmaceutical expansion’s HVAC is defined by the product, not the tonnage. Two blocks with the same cooling load can need entirely different air systems: one keeps packing staff comfortable; the other must hold a pressure cascade, filter its supply to a defined cleanliness, keep humidity in a band through the monsoon, and prove it all in qualification documents. A bigger chiller fixes none of that.

This brief is for project and engineering heads planning a new block, a line extension or an upgrade. The baseline is revised Schedule M to the Drugs Rules, 1945 — “Good Manufacturing Practices and Requirements of Premises, Plant and Equipment for Pharmaceutical Products” — substituted by G.S.R. 922(E) of 28 December 2023. It gave large manufacturers (turnover above ₹250 crore) six months and small and medium manufacturers twelve months to implement it; G.S.R. 127(E) of 11 February 2025 extended the date to 31 December 2025 for small and medium manufacturers that applied in Form A with an upgrade plan. Check CDSCO for any later notification affecting your unit.

Process-specific room requirements

Start from a room data sheet for every room, written by production and quality with the HVAC designer: it is the user requirement the design, the price and the later qualification are measured against. Schedule M (Part I, 12.6.7) requires production areas to have air-control facilities — filtration sufficient to prevent contamination and cross-contamination, temperature and, where necessary, humidity control — appropriate to the products, the operations and the external environment, and monitored during production and non-production periods.

For sterile products, Part II of Schedule M is specific: four grades of clean area. Grade A is classified at ISO 4.8 (set by the ≥5.0 µm particle limit), Grade B at rest at ISO 5, Grade C at ISO 7 at rest and ISO 8 in operation, and Grade D at rest at ISO 8, using the ISO classification methods it references. Part VIII, for oral solid dosage forms, has no grade table of its own; it sets out pressure-cascade logic instead, below.

Pressure and filtration strategy

The pressure regime is a product decision before it is an HVAC one. Schedule M sets out the logic for two common cases:

• Oral solid dosage (Part VIII). Air moves from a clean corridor into the processing cubicles so dust is contained: the corridor above the cubicles, and the cubicles above atmospheric pressure. Highly potent products are made under a cascade negative to atmosphere. The cascade is assessed for each facility; differential limits are set so that adjacent rooms’ operating ranges cannot overlap; lower differentials can be acceptable where sink or bubble airlocks segregate areas; and pressure devices are calibrated, qualified and alarmed at limits set by risk analysis.
• Sterile products (Part II). Filtered supply air keeps each area positive to surrounding areas of a lower grade, with a guidance value of about 10 to 15 Pa between adjacent rooms of different grades, pressure indicators where the difference matters, regular records, and an alarm on air-supply failure.

Filtration follows the grade or class and the containment need: staged filters at the air-handling unit, terminal HEPA filters where the grade calls for them, and exhaust filtration where potent dust must not leave the building. For sterile areas, Part II asks for an installed leak test of HEPA filters to ISO methods at a recommended six-monthly interval and not more than twelve months apart — a recurring operating cost, not only a project one.

Three North Indian conditions need explicit design cases: monsoon humidity, which can break a cascade and humidity band that held in a dry June; dust, which loads pre-filters faster on industrial corridors; and power interruptions, which collapse the cascade — so recovery on DG changeover belongs in the design and in operational qualification.

Segregation and cleanability

An upgrade inside an existing building inherits its ceilings, joints, shafts and service routes. Schedule M’s premises requirements decide what has to change around the ductwork:

• Layout and flow. Premises designed for a logical flow of materials and personnel, preferably with production areas connected in the order of operations and cleanliness levels (Part I, 12.2.10 and 12.6.2).
• Dedicated facilities. Dedicated, self-contained facilities for products such as highly sensitising materials (for example penicillins) and biological preparations; certain other highly active products not made in the same facilities, with campaign working only in exceptional cases with validated precautions (12.6.1). On a mixed site this can mean a separate air-handling system, not just a separate room.
• Surfaces and services. Where materials or products are exposed, walls, floors and ceilings smooth, free from cracks and open joints, not shedding particles and easy to clean; pipework, light fittings and ventilation points sited to avoid recesses and, where possible, maintained from outside the manufacturing area (12.6.4–12.6.5).
• Cross-contamination. Airlocks, pressure differentials and air supply and extraction designed to prevent it, and the risk from recirculated or re-entering untreated air minimised (18.3.3).
• Doors and airlocks. In oral solid dosage areas, doors open to the high-pressure side with self-closers, and airlock doors interlocked or alarmed as the risk assessment decides (Part VIII, 1.21); in sterile areas, airlock doors must not open simultaneously (Part II, 8.8).

This is why converting part of an existing shed can be better done as a room-in-room enclosure with its own envelope than as a retrofit of the old fabric.

Decision table: upgrade, extend or build new

Qualification documents and competent review

Schedule M (Part I, section 5) requires qualification and validation to provide documentary evidence that premises, supporting utilities and equipment are designed to GMP requirements (design qualification), installed to their design specifications (installation qualification) and operate to them (operational qualification), and that the process consistently produces product to specification (process validation, also called performance qualification). Significant changes that may affect quality must themselves be qualified and validated, qualification is not a one-off exercise, and planned changes are approved before implementation, taking into account regulatory notification and approval where required. For an expansion, that means three working rules:

1. Put the documents in the HVAC contract. Design-qualification inputs, installation and operational test protocols, air-balancing results, filter integrity tests, airflow visualisation where required, pressure and recovery tests, calibration certificates, and the diagrams of pressure cascades, airflow directions and personnel and material routes that Part VIII (1.67) asks to be prepared and maintained should be named deliverables. If a record is not a deliverable, nobody is obliged to produce it.
2. Run it through change control from the start. The manufacturer’s quality unit owns qualification and approves the protocols; the contractor executes and records. Whether the change also needs intimation to, or approval from, the licensing authority is for the manufacturer’s regulatory team to establish.
3. Get a competent review of the design. A designer with pharmaceutical HVAC experience should review the room data sheets, pressure and airflow diagrams and the controls philosophy before procurement. The WHO Technical Report Series guidance on HVAC, which Schedule M says may be considered for general guidance, is a useful reference for that review.

None of this makes a plant GMP-compliant by itself; compliance comes from the manufacturer’s whole quality system, of which HVAC is one part.

Next steps

For a quick check of airflow at a given air-change rate, the ventilation and air-change calculator converts room volume and air changes into airflow; cleanroom air-change rates themselves come from the grade, the room and the recovery requirement. Secured Engineers designs and builds cleanroom HVAC and hands over the test records the client’s quality team uses for qualification, with design and statutory filings through its design and approvals service. For a project-specific review, send the facility use, the process requirements (room data sheets if you have them) and the proposed expansion through the quote request. Related reading: MEPF for WHO-GMP pharma facilities and the approvals that overlap on a pharma cleanroom; other new-project and expansion guides are collected in Insights.

Food plants follow a different rulebook — FSSAI licensing and customer or certification-scheme requirements rather than Schedule M — but the same HVAC logic of zoning, pressure, filtration and cleanable construction applies; see food processing facilities.

Sources and how to verify

• Revised Schedule M, G.S.R. 922(E), 28 December 2023 — Ministry of Health and Family Welfare, via CDSCO; Part I (sections 5, 12 and 18), Part II (sterile products) and Part VIII (oral solid dosage forms).
• G.S.R. 127(E), 11 February 2025 — extension to 31 December 2025 for small and medium manufacturers that applied in Form A.
• National Building Code of India 2016 (SP 7:2016) — Bureau of Indian Standards; Part 4 Fire and Life Safety and Part 8 Building Services for the building around the cleanroom.

Confirm locally: the manufacturer’s quality and regulatory teams decide the grades, the qualification scope and any intimation to the licensing authority; check CDSCO and your state licensing authority for notifications issued after these.