Commercial kitchen hood and duct systems must comply with which of the following standards?

The correct choice is ANSI/UL 300 because this standard specifically addresses the requirements for fire suppression systems installed in commercial cooking environments, particularly within hood and duct systems. ANSI/UL 300 emphasizes the need for systems to effectively combat the unique fire hazards present in commercial kitchens, such as those caused by cooking oils and fats.

This standard outlines the necessary performance criteria for both automatic and manual extinguishing systems, ensuring that they can adequately suppress fires that could escalate in the cooking areas. Compliance with ANSI/UL 300 is essential for ensuring the safety of commercial kitchens, as it provides guidelines and testing protocols that help prevent the spread of fire and protect property and lives.

In contrast, the other options—ANSI/UL 250, ANSI/UL 400, and ANSI/UL 600—are standards that pertain to different types of equipment or systems and do not specifically focus on the fire suppression needs required for commercial kitchen hood and duct systems. This is why they are not the correct choice in the context of the question.