English: This is a graphic depiction of a room on fire and what happens when proper firestops are not present. We have fuel for our fire. It burns and gives off flames and smoke. If there is a lot of plastic, such as PVC, polyvinylchloride, the chloride part separates and bonds with moisture in the air. Hydrochloric acid forms, which is lethal. It also corrodes electrical contacts and can decimate electronic equipment. (Continuity of Operations…). Heat rises. We have higher pressure near the top of the room and lower pressure towards the floor. Somewhere in there, we have a neutral plane of pressure. This, by the way, is what is re-created in fire testing of certified fire protection products, such as wall and floor systems and firestops. If I have holes in the ceiling or at the top of the walls, the high pressure inside the room ensures that highly toxic, corrosive, re-ignitable flue gases are distributed way beyond that room. It does not take a lot of fuel to generate a lot of smoke. And that is what causes the majority of fatalities. If there are openings in the walls, closer to the floor, or in the floor, and they are not properly firestopped, fresh oxygen enters room, to make things worse. Of course, if your building is held up with unprotected steel, this will first expand and then soften and collapse, unless suppression methods are successfully employed.