Assuming a negative air filtration unit pulls 2,000 cubic feet per minute, how many units would be required to maintain sufficient negative pressure in the area, with one extra unit as back-up?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (B)

Maintaining containment relies on having enough exhaust air to keep the area under negative pressure, and you always include a spare unit so the system stays effective if one unit is down for maintenance or fails.

If the scenario calls for two units to achieve the required negative pressure, adding one extra unit for back‑up brings the total to three. With each unit moving 2,000 CFM, three units provide up to 6,000 CFM of exhaust capacity, helping ensure the area remains negative even if one unit isn’t operating momentarily. Using four or five would go beyond what the setup intends, whereas three units match the need plus redundancy.