Why is negative pressure used in HD containment rooms?

• A. To push aerosols out to surrounding areas
• B. To maintain positive pressure in the room
• C. To regulate room temperature
• D. To ensure air flows into the room and HD aerosols do not escape to surrounding areas

Answer: (C)

The idea is to create a pressure difference that keeps contaminants contained. In a negative-pressure room, the air inside is at a lower pressure than the surrounding areas. Because air moves from higher to lower pressure, this causes air to be drawn into the room rather than pushed out into the hall. The room is equipped with an exhaust system that continuously removes this air (often through HEPA filtration) so any aerosols stay inside long enough to be captured and treated before the air is released outside. This setup prevents HD aerosols from escaping to other parts of the facility and protects staff and nearby areas. Temperature control is handled separately by the building’s HVAC, not by the purpose of maintaining negative pressure. If a room were at positive pressure, aerosols could be forced into adjacent spaces, which is undesirable for containment.