Every sub roll Firehouse offers, including both gluten-free options, contains a seed oil, and the white and wheat rolls carry an additive as well, so no standard sub avoids either.
Firehouse Subs publishes ingredient statements for its full menu through its own ingredient search. Of 185 food components, 68 contain a named seed oil and 83 contain an additive from our watchlist. The decisive finding is the bread: the Large White Sub Roll and the Large Wheat Sub Roll both contain a seed oil and an additive, and even the Gluten Free Ciabatta Roll and Gluten Free Hoagie Roll contain a seed oil, so there is no roll on the menu that avoids one. The garlic bread in all three sizes and the garlic mayonnaise are the same story. Their meats and cheeses are steamed rather than fried and several read clean, but a Firehouse sub is defined by its roll and the roll is the problem.