How Is Hospital HVAC Zoning Engineered for Infection Control?

The ventilation schedule is the project's infection-control contract. For every room, it lists the pressure relationship to adjacent spaces, total and outdoor air changes per hour, filtration levels for supply and recirculated air, and the design temperature and humidity range. The schedule is coordinated with the architectural floor plans so the pressure map can be read spatially: positive zones in one color family, negative in another, with the cascades visible at a glance. Special spaces get special attention. Operating rooms, isolation rooms, pharmacies, laboratories, and sterile processing each carry unique combinations the standard spells out, and rooms that can change function, such as isolation-capable patient rooms, need designs that satisfy both modes. The schedule also documents which spaces must maintain their relationships on emergency power, because containment that fails during an outage is not containment.

Air handling systems are grouped by pressure family and criticality. General patient floors can share systems zoned by floor or wing, while the OR suite, isolation areas, and other critical zones get dedicated systems so maintenance or failure in one area never affects another. Redundant supply and exhaust fans with automatic changeover keep pressure relationships alive through equipment failures. Ductwork quality is a pressure-control issue. Sealed duct construction, minimal leakage, and careful damper selection let the test-and-balance contractor actually achieve the design differentials. Exhaust systems for isolation and decontamination run dedicated to outdoors, and the design accounts for filter loading, door traffic, and seasonal stack effects so the pressure map holds on the worst day, not just on the balancing report.

Use this checklist during design and plan check: • Room-by-room ventilation schedule per ASHRAE 170: pressure, air changes, filtration • Pressure map coordinated with floor plans showing every cascade spatially • Air systems grouped by pressure family with critical zones on dedicated systems • Redundant fans with automatic changeover for systems serving critical areas • Sealed ductwork and selected dampers capable of holding small differentials • Dedicated exhaust to outdoors for isolation, decontamination, and lab spaces • Building automation monitoring pressure relationships with drift alarming • Commissioning of every pressure relationship in normal and emergency power modes