What is the function of 'two independent means of ventilation' in B28?

• A. Redundancy to ensure continuous dilution of leaked refrigerant even if one ventilation path fails
• B. To increase cooling rate only
• C. To reduce energy use
• D. To complicate maintenance

Answer: (A)

Two independent means of ventilation are required to keep the area safe when a flammable refrigerant leaks. In these systems, the goal is to keep vapor concentrations below the flammable limit by diluting any leaked refrigerant with fresh air. If ventilation relied on a single path, a blockage, fan failure, or maintenance work could eliminate dilution and allow vapors to accumulate to dangerous levels. Having two separate, independent ventilation paths ensures that even if one path is disrupted, the other continues to remove and dilute vapors, maintaining a safer environment. The independence of the paths—often separate ducts or fans and power sources—reduces the chance that a single fault will disable the entire ventilation system, which is exactly why redundancy is emphasized in B28.