Final answer:
ESFR sprinklers are fast-acting fire suppression systems that release water to suppress fires quickly. They are heat-activated, not smoke-activated, and do not need to be manually switched on.
Step-by-step explanation:
Early Suppression Fast Response (ESFR) sprinklers are high-volume, high-velocity fire suppression systems that are designed to respond quickly and release a large amount of water directly to the fire, suppressing it before it can grow. The correct answer to the question is 1) Sprinklers that activate quickly to suppress fires. Unlike traditional sprinkler systems that control the spread of the fire until firefighters can arrive, ESFR sprinklers are designed to suppress a fire much more rapidly, meaning they are often used in environments such as warehouses or storage facilities where highly combustible materials are present. These sprinklers are triggered by heat, not smoke, and they do not require manual activation.