WHO TRS 986 – Points 11.9–11.10 (as used in Risk-Based Inspection checklists) sit under HVAC/Air-handling controls and focus on preventing cross-contamination and re-entrainment of contaminated exhaust air back into clean areas. CDSCO
11.9: Exhaust systems must be safely filtered/scrubbed before discharge
Inspectors verify whether all exhaust systems (e.g., dust extraction, vacuum exhaust, fluid bed dryer exhaust, coating pan exhaust, etc.) are routed through safe-change filter housings (often bag-in/bag-out type) and/or wet scrubbers before being exhausted to the atmosphere.
What they check in practice:
- A complete list of exhaust sources and their designed control method (filters/scrubbers). CDSCO
- Engineering evidence: schematics, AHU/exhaust drawings, filter type/grade, DP gauges, and airflow direction.
- SOPs + records for safe filter change (to protect product and personnel), cleaning of ducts, and safe disposal of contaminated filters/dust. CDSCO
- Whether measures are in place to avoid dust escape during powder operations (WHO GMP also expects controls where dust is generated).
11.10: Exhaust discharge points must prevent re-entrainment
Inspectors verify that exhaust outlets outside the building are located as far as possible from air entry points/exit points and at a high level, so exhausted air cannot be drawn back into fresh-air intakes or doors/windows (re-entrainment).
What they check in practice:
- Layout showing exhaust stacks vs. fresh-air intakes, personnel doors, AHU intake louvers.
- Justification for stack height/direction (site wind pattern/nearby structures), and maintenance access.
- Evidence the HVAC/ventilation design supports product protection and does not adversely affect operations. ECA Academy
Overall, 11.9–11.10 demonstrate that your facility’s exhaust handling is engineered to capture contaminants at source and keep them from coming back into controlled areas.