What is the primary purpose of a negative pressure room in chemical or biological work?

• A. To increase the spread of contaminants in the facility
• B. To maintain equal pressure with adjacent spaces
• C. To prevent outside air from entering the room
• D. To prevent contaminated air from escaping to adjacent spaces by maintaining lower pressure inside the room

Answer: (D)

Controlling airflow through pressure differences is how containment is achieved in chemical or biological work. A negative pressure room is kept at a lower pressure than surrounding spaces, so air tends to flow from the outside into the room rather than from the room to the outside. By exhausting more air than is supplied, any contaminants generated inside are carried out by the exhaust system, preventing them from escaping to adjacent areas and protecting people and other rooms. That’s why the primary purpose is to prevent contaminated air from escaping to adjacent spaces by maintaining lower pressure inside the room. The other options don't fit this goal: increasing spread would occur if the room weren’t at a lower pressure, equal pressure would defeat containment, and while outside air can enter, the point isn’t to stop it but to ensure inward flow keeps contaminants contained.