Hygienic Ventilation for Hospitals and Healthcare Facilities

In healthcare facilities, ventilation is a direct part of infection control. Keeping the particle and microorganism load under control, directing air movement between rooms and providing stable temperature and humidity in sensitive areas are the three basic jobs of hospital ventilation.

Operating theatres

The operating theatre is the most sensitive room in the facility. Low-turbulence clean air is supplied downwards from the ceiling over the operating table; this air curtain separates the sterile field from the surrounding air. Extraction is at low level on the walls, so particles are swept from top to bottom.

The operating theatre is kept at positive pressure relative to its surroundings; when the door opens, corridor air does not flood in. Temperature and humidity must be adjustable, because different surgical specialties have different preferences.

Sound level is a design criterion here. A high air change rate increases noise; duct velocities and silencers are selected accordingly.

Intensive care and isolation rooms

In intensive care the patient is protected; the room is kept positive and supplied with filtered air. In infectious disease isolation rooms the direction is reversed: the room is kept negative, air does not escape and the exhaust is filtered before discharge.

Where both requirements are on the same corridor, an anteroom is used. The anteroom acts as a pressure buffer between the two spaces.

Laboratories and sampling areas

Microbiology and pathology laboratories contain biosafety cabinets and fume cupboards. The exhaust of this equipment must be balanced together with the room ventilation; when a fume cupboard runs, the room's pressure balance must not be disturbed.

In sample and reagent storage areas, temperature stability becomes important.

Central sterilisation

In the sterilisation unit, a staged pressure difference is set up between dirty, clean and sterile zones. Air always flows from the sterile side to the dirty side. The autoclave area also has a high heat and humidity load; this area is assessed separately.

Validation and maintenance

In hospital ventilation it is proven by measurement that the system works: terminal filter airflows, air change rates, pressure differences, HEPA leak test, particle count and recovery time. Measurements are reported and repeated at set intervals.

Filters are changed according to differential pressure, not the calendar; the leak test is repeated after each change.

Patient rooms and general areas

In patient rooms, outpatient clinics and waiting areas outside the sensitive rooms, the priorities are fresh air quantity and comfort. Waiting areas have very variable occupancy through the day; adjusting the fresh air ratio to demand with a carbon dioxide sensor protects comfort and lowers energy consumption.

Kitchen, laundry and waste areas

The hospital kitchen follows the rules of commercial kitchens: canopy hood, grease filters, exhaust and fresh air balance, and regular duct cleaning. The laundry has a high humidity and heat load; a pressure cascade is set up between dirty and clean linen zones. Waste collection areas are kept negative and their air is exhausted so that it never returns to patient areas.

Continuous operation

Ventilation in a hospital cannot stop. That is why systems serving critical rooms are designed with redundancy and maintenance is planned so it can be done without taking the room out of service. Placing access points for filter changes correctly is the most basic part of this plan.