I’ve been eating here for years. I usually get a chopped salad or a sub with a gluten free bun. The buns are very small but I do enjoy their subs. Their website has an allergen menu where you can filter out what allergens you have. They list all the toppings and meats you can get. I wish it was a little more simple and they would list what specialty subs can be made without the allergens. I don’t know how safe the facility is for anyone who is very sensitive to gluten.
I love that they offer gluten-free rolls and my favorite is "The Engineer" hoagie sandwich with sautéed mushrooms and onions on top. If you are extremely sensitive, there may be CC issues since they make subs with gluten bread. But I have not had any problems at Firehouse Subs, and have eaten at many different ones, quite a few times.