21 CFR 211.42 - Design and Construction Features of Buildings and Facilities

What it says

Buildings used in manufacturing, processing, packing or holding of drug products must be of suitable size, construction and location to facilitate cleaning, maintenance and proper operations, with adequate space to prevent mix-ups and contamination, and specific design features required for aseptic processing areas.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• Facility design is assessed against operational reality, not architectural intent - a building that looked adequate on paper can still fail this requirement if actual workflow creates contamination or mix-up risk.
• Adequate space is a functional test, not a minimum square footage figure - the question is whether the space genuinely prevents mix-ups and cross-contamination given the actual processes performed there.
• For aseptic processing specifically, this provision anchors the more detailed airflow, pressure differential and material flow requirements that environmental monitoring and contamination control programmes are built around.

What FDA inspectors look for

• Whether personnel and material flow patterns, observed during a facility walkthrough, actually match what design documentation claims.
• Whether cross-contamination risk between different products or process stages has been assessed based on real adjacency and airflow, not just a floor plan.
• For sterile facilities, whether pressure differentials and classification zones are maintained and monitored consistently with the facility's design basis.

Related regulations