A powerful way to intercede for all firefighters is to offer a prayer to St. Florian. He is known as the patron saint of firefighters based on legends of his life.
St. Florian was a Roman solider in the 3rd century who was reportedly in charge of a special group of firefighting soldiers. According to the 19th-century book Sacred and Legendary Art, this involved his swift action to douse the flames threatening a city.
Ever since then, he has been associated with firefighters, and many have called upon his intercession to ask for God's protection over them.
Here is a popular prayer to St. Florian, often prayed by firefighters for heavenly assistance.