Which statement about laboratory ventilation design is correct?

• A. Lab air leaves the lab through the fume hoods.
• B. Air enters the labs through heating/cooling ducts and hallway air.
• C. Hallway air flows into the lab.
• D. The atmospheric pressure in the lab is greater than the hallway.

Answer: (A)

In lab ventilation, removing contaminants from the room is achieved by an exhaust path, with fume hoods serving as the primary local exhaust. Fume hoods are designed to pull air from the room through the sash and into the hood, carrying any vapors or fumes out to the exterior. This creates a protective flow path directly at the source of potential exposure. Therefore, saying that lab air leaves the lab through the fume hoods reflects the essential role of the hood exhaust in maintaining safety.

Air supply does come into the room through ducts and diffusers to replace the exhausted air, but that supply is separate from the deliberate exhaust path that removes contaminants. The other statements touch on pressure relationships or where air enters, but they do not describe the main mechanism by which contaminants are actually removed from the space.