Infrared marking devices and methods for marking an object, such as a door, inside a structure, such as a smoke-filled or burning structure. The infrared marking device comprises a ring-shaped, elasticized outer sleeve having a tubular sidewall and an amount of a self-heating material confined inside the tubular sidewall of the outer sleeve. The self-heating material emits infrared radiation when activated to initiate an exothermic chemical reaction. The infrared radiation is visible in a thermal imaging camera. The method comprises activating a self-heating material confined inside a marking device to initiate an exothermic reaction that emits infrared radiation and applying the marking device to an object inside the structure.