Describe what a scrubber does in air pollution control and name a pollutant it commonly treats.

• A. A scrubber removes pollutants from gas streams by contacting with a liquid; commonly treats sulfur dioxide (SO2) and hydrogen chloride (HCl).
• B. A scrubber uses a particulate filter to remove dust from gas streams.
• C. A scrubber removes pollutants by converting them into harmless salts through chemical reaction with catalyst.
• D. A scrubber is a device that reduces humidity in the air.

Answer: (A)

A scrubber cleans gases by bringing the polluted gas into contact with a liquid, so pollutants dissolve into the liquid or react with it and are pulled out of the gas stream. This mechanism makes scrubbers especially effective for acid gases that dissolve easily in water, such as sulfur dioxide and hydrogen chloride. In practice, a wet scrubber sprays water or a chemical solution into the gas stream, forming a liquid phase that captures the contaminants while the cleaned gas exits. This approach is different from filtration, which uses a solid barrier to trap particles, and different from catalytic systems, which rely on a solid catalyst to drive chemical reactions without a liquid wash. It’s also not about removing moisture from air, which is a humidity control goal rather than a pollutant-removal objective.