Positive Pressure Rooms & Negative Pressure Rooms

Overview of Pressure-Controlled Isolation Rooms

Positive and negative pressure rooms are specialized hospital environments engineered to control airborne contamination through precise air pressure differentials. These rooms are critical in infection prevention and control, protecting either vulnerable patients from external pathogens or healthcare workers and the environment from highly infectious patients.

Both room types rely on advanced HVAC systems with HEPA filtration, directional airflow, monitoring devices, and airtight construction to maintain required pressure gradients (typically 2.5–8 Pa difference).

Positive Pressure Rooms

Also known as Protective Environment (PE) rooms, these are used for patients with weakened immune systems (e.g., post-transplant, chemotherapy, severe neutropenia) to shield them from infections.

• Prevents entry of airborne contaminants from corridors and adjacent spaces
• Maintains ISO Class 5–7 cleanliness with HEPA-filtered supply air
• Typically 12–15+ air changes per hour (ACH)
• Positive pressure differential of +2.5 to +8 Pa relative to adjacent areas
• Used in bone marrow transplant units, burn units, and oncology wards

Negative Pressure Rooms (Airborne Infection Isolation Rooms - AIIR)

These rooms are essential for managing patients with airborne infectious diseases such as tuberculosis (TB), measles, varicella (chickenpox), SARS-CoV-2 (during aerosol-generating procedures), and other highly transmissible respiratory pathogens.

• Contains infectious aerosols within the room → protects staff, visitors, and other patients
• Exhaust air is HEPA-filtered or exhausted directly outdoors
• Minimum 6–12 ACH (higher for certain pathogens)
• Negative pressure differential of –2.5 to –8 Pa relative to adjacent areas
• Commonly required in emergency departments, ICUs, and infectious disease units

Key Comparison: Positive vs Negative Pressure Rooms