By Steve Weyel
Building owners know fire can destroy a building in minutes. They are also aware that active and passive fire protection equipment play important roles in keeping the structure and its occupants safe.
What is not as well-known is how fire-rated floor doors play an essential role in passive fire protection. Building codes classify two types of doors for fire-rated openings in horizontal assemblies: fire-rated floor doors and fire-rated access doors. Each of these door types meet specific fire protection requirements for the applications in which they are intended. Fire-rated floor doors have a fire resistance rating. Fire-rated access doors have a more stringent fire protective rating.
Doors with fire protective rating address heat transfer and include intumescent coatings. Both are important to understand for specifiers and how they factor into design.
Heat transfer
When a fire erupts, everyone can see flames and the inherent danger they represent. What is less well-known, however, is how the fire started. This is especially important to recognize in buildings, where concealed spaces house wiring and other materials that could trigger a blaze.
For fire to occur, three components—heat, fuel, and oxygen—are needed to ignite and sustain it. All these elements in the “fire triangle” are required. If one is removed, the fire will be extinguished. A fire starts when all three elements are present in the right proportions and danger develops when fire spreads. Heat from fire transfers through convection, conduction, radiation, or direct burning. For commercial property owners, convection and conduction fires are of particular importance.
Most fire protection experts report convection fires are most common in domestic and commercial buildings. Fire causes the air around it to heat and produces smoke. Warm air rises, but the heat is trapped when it hits a ceiling and begins to travel horizontally. As the fire spreads, combustible materials will also ignite and fuel the fire.
Conduction fires spread when materials contact each other. Heat energy is transmitted through collisions between atoms and molecules. It occurs more readily in solids and liquids, and the rate of energy transfer is higher when there is a large temperature difference between materials that are in contact.
