Which method of ventilation involves roof or floor openings for the escape of a contaminated atmosphere?

The method of ventilation that utilizes roof or floor openings to facilitate the escape of a contaminated atmosphere is referred to as vertical ventilation. This technique is commonly employed in fire and rescue operations, particularly when dealing with structures that contain smoke or toxic gases. By creating openings at higher or lower points in a building—such as on the roof or through floors—contaminated air is allowed to rise and exit, while fresh air can enter the structure. This movement of air helps to enhance visibility, improve conditions for occupants, and support firefighting efforts by reducing the intensity of the heat and smoke present.

Vertical ventilation is particularly effective because it takes advantage of the natural behavior of smoke and heat, which rise, thus creating a more efficient pathway for their exit. Additionally, it minimizes the risk of spreading contaminants to other areas of the building, making it a preferred method in emergency situations.