An automatic sprinkler system must be installed in commercial kitchen __________ when using alternative automatic fire extinguishing systems.

An automatic sprinkler system must be installed in commercial kitchen exhaust hoods and duct systems when alternative automatic fire extinguishing systems are used. This requirement is based on the need for comprehensive fire protection in areas that are especially prone to ignition and fire spread due to cooking operations.

Exhaust hoods are critical because they capture heat, smoke, and combustion particles from cooking equipment. If a fire were to start in the kitchen, the heat and flames could easily travel through the exhaust hood and ducts, potentially spreading to other areas of the building if not properly managed. Therefore, integrating an automatic sprinkler system in these spaces helps ensure that any fire is promptly detected and suppressed, reducing the risk of major incidents.

In contrast, the other options would not provide the same level of coverage and protection as sprinklers installed in both the exhaust hoods and duct systems. This comprehensive approach is vital in maintaining a safe environment in commercial kitchens, where grease fires and other hazards are prevalent.