To limit the probability that ice and snow will accumulate on treads and landings of exterior exit stairs, which could lead to delays in the evacuation or movement of persons to a safe place in an emergency, which could lead to harm to persons.
To limit the probability that ice and snow will accumulate on treads and landings of exterior exit stairs, which could lead to emergency responders being delayed or ineffective in carrying out their emergency response operations, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.
To limit the probability that exterior exit stairs will be obstructed or slippery, which could lead to persons tripping, slipping or falling, which could lead to harm to persons.