Which action specifically removes the source of indoor air contaminants?

• A. Ventilate with fresh air
• B. Remove the source
• C. Obstruct modes of transmission
• D. Control humidity

Answer: (B)

Removing the source is the most effective way to prevent exposure because it eliminates the contaminant at its origin, so nothing is released into the air to begin with. Ventilating with fresh air helps by diluting what's already there, but it doesn't stop the contaminant from being produced or released by the source itself. Controlling humidity can reduce growth or release of certain contaminants, yet it doesn’t remove the contaminant source set in place by ongoing emissions. Obstructing modes of transmission addresses how contaminants travel or spread, not where they come from, so it doesn’t remove the source. By taking away or eliminating the source—such as removing a pollutant source, replacing a materials with low-emission options, or fixing the condition that generates contaminants—you directly stop the contamination from entering the indoor environment.