noun
emergency staircase; fire escape
Refers to an external or internal staircase designated for emergency evacuation, commonly found in buildings.
火事のときは非常階段を使ってください。
Please use the emergency staircase in case of fire.
このビルには非常階段が二つある。
This building has two fire escapes.
避難階段 is a more technical term for evacuation staircase, often used in building codes, while 非常階段 is the common everyday term.
Compound of 非常 (emergency) and 階段 (stairs, staircase).