Why are back-draft or relief dampers sometimes required in kitchen exhaust designs?

Why are back-draft or relief dampers sometimes required in kitchen exhaust designs?

• A. To prevent reverse airflow when there is negative pressure or door openings and to protect the space from infiltration.
• B. To increase air velocity in the duct.
• C. To reduce maintenance costs.
• D. To improve aroma.

Answer: (A)