51. According to 46 CFR Subchapter T, how long should exhaust blowers be operated in enclosed spaces containing gasoline powered machinery before starting the engine?

46 CFR Subchapter T requires exhaust blowers to operate long enough to achieve at least one complete change of air in enclosed spaces containing gasoline-powered machinery before engine startup. This performance standard accounts for varying compartment volumes and blower capacities, and reliance on smell is unsafe due to the potential for explosive vapor concentrations even without a strong odor.