A chemical agent is released directly outside the lobby of a high-rise building. Which area is considered to be "the rest of the building"?

• A. An office on the 20th floor with no outdoor air intake fans
• B. An office on the 20th floor with outdoor air intake fans
• C. An office on the 1st floor without outdoor air intake fans
• D. A lobby near the entrance

Answer: (A)

Ventilation paths determine where outdoor air—and anything it carries—can reach inside a high-rise. The “rest of the building” refers to areas that are not fed by outdoor air intakes, so they aren’t exposed to outdoor air coming in through the building’s ventilation system.

An office on a high floor that has no outdoor air intake fans would not be drawing in outdoor air, so it wouldn’t receive the contaminated outdoor air from the release. That makes it a part of the building that’s effectively isolated from the external air supply and, therefore, considered the rest of the building in this scenario. The lobby near the entrance would be directly in the path of outdoor air entering the building and would likely be contaminated, and a floor with outdoor air intake fans would actively bring in outdoor air (and any contaminants) as well. An office on the first floor without outdoor air intake fans could still be influenced by air coming in from outside or from adjacent spaces, so it’s less clearly isolated than the high-floor space without intakes.