Short answer: not really—at least not as a standard, code-approved product. Fire escapes are designed as emergency exits, and most building and fire codes treat them as means of egress. That means anything that blocks, narrows, or creates a tripping or ignition risk—including planter boxes—can be prohibited. A few companies sell railing planters, hook-on balcony boxes, or custom narrow troughs that may physically fit a fire escape railing, but they are not automatically legal or safe just because they fit.
If you want to garden on a fire escape, start with the rules, not the planter. Check your local fire code, lease, HOA rules, and ask your landlord or fire marshal. Many cities require fire escapes to remain completely clear. Even a lightweight box can obstruct a ladder, landing, window, or path during a panicked exit.
If you get permission, choose a purpose-built railing planter with a very low profile. It should be made of non-combustible or fire-resistant material, such as powder-coated aluminum or galvanized steel, and attach securely to the outside of the railing without drilling if drilling is banned. Avoid plastic that can melt, dried leaves, peat moss, and vines that hang into the ladder route. Keep plants small, water carefully to prevent runoff or ice, and make the box easy to remove in seconds.
For most urban gardeners, the safer answer is to skip the fire escape. Use a balcony railing planter, a window box that opens inward, a wall-mounted vertical garden, or a community garden plot instead. If a product is marketed as a "fire escape planter," read the fine print: it may fit the railing, but that does not mean it meets fire code. Safety and legal compliance come before curb appeal.