What 29 CFR 1910.37 requires (plain English)
29 CFR 1910.37 governs the maintenance, safeguards, and operational features of exit routes: the continuous, unobstructed paths that let employees leave a workplace during an emergency. A well-designed exit route is worthless if it is blocked, dark, locked, or unmarked when a fire or other emergency strikes, and this standard exists to keep every exit route usable at all times. It complements 1910.36 (design of exit routes) and the emergency action plan requirements of 1910.38.
The core duties are simple and strict. Exit routes must be kept free and unobstructed: no materials or equipment may be placed in an exit route, even temporarily, and the route may not be blocked by furniture, stock, snow, or a locked door. Each exit route must be adequately lighted so an employee with normal vision can see along it, and each exit must be clearly visible and marked by a sign reading "Exit" in plainly legible letters at least six inches high, with directional signs where the path to the exit is not obvious.
Exit-route doors must be free of decorations or signs that obscure their visibility, and safeguards designed to protect the route (such as fire-resistant separations and self-closing fire doors) must be kept in good working order. The locking rule itself sits in the companion section: 1910.36(d)(1) requires that employees be able to open an exit route door from the inside at all times without keys, tools, or special knowledge, while permitting a panic bar that locks only from the outside. Because these failures are easy for an inspector to see and directly life-threatening, blocked or locked exits are a recurring source of serious citations.