Hollow Metal Doors are an important part of the security and the fire resistance of a commercial building. Often these are used as an outside door such as a fire escape door leading out onto the street as opposed to a glass entrance door made of aluminum.
Because of the heavy duty use of these doors and the fact that they need to be built to meet fire resistance standards, there is a specific testing process they undergo to meet UL standards.
These strict guidelines ensure that hollow metal fire rated doors have the correct fire protection rating to keep the occupants of a building safe in the event of disaster.
Materials Used for the Metal Doors
When talking about frames and hollow metal doors, it is important to know there are different materials used to make these doors that could impact their fire resistance. Cold rolled, hot rolled, galvannealed, galvanized, and stainless steel materials are all often used and tested based on the UL safety standards.
The standards these doors meet will determine the level of fire safety protection, in terms of rating, the doors will receive on their label.
Are All Steel Doors Fire Rated?
Yes, but just because a steel door is "rated" means that it meets your local code standard. You need to know what kinds of tests are applied and how to match those capabilities with your local regulations.
The doors go through a very diligent testing system, not only to test the materials against fire, but also the closing devices used. Given that there are different designs available for these doors, the performance levels will also differ in terms of frame and door assembly.
Anyone installing these metal doors must understand the need for fire resistance and properly assemble and install the metal doors, to ensure that they meet the required criteria for local fire codes.
Building codes are specific to cities, states, even countries and therefore it is important to follow your local code guidelines for the type of building and the associated codes it must meet.
For example, the requirements for what type of hollow metal door used is often based on the use of a building, and how many people will occupy it at a given time.
Door fire ratings are based on time. A rating may be given for 20 minutes, up to 3 hours, based on the exposure to flame the assembly and door can handle when it encounters fire. The test examines the hardware, the wall, and the full hollow metal door assembly as per building code standards.
A large furnace is used to test the door against it’s specified rating. The door and wall will be placed in a gas fired furnace in which high temperature flames are blasted against the door assembly, while both sides are monitored for structural integrity and flame spread. During fire exposure the door will go up in temperature to ensure it can handle the rating the increased intensity of a growing fire without compromise.
Other parts of the door are also tested in this process. ANSI/UL10 and UBS 7-2 for example are used to test the cotton or foam padding in the door.
Will the pad crack, will there be openings, or seams in which hot gases will be able to escape in the first half hour of the test?
Once the testing is complete the door assembly is removed then subject to further testing including impact, cooling, and erosion.
During the cooling process water at a specific pressure, from a 2.5 inch hose with 28mm nozzle will be used to conduct a hose stream test on any door rated over 20min. During this water test, the stream cannot dislodge any glass over more than 5% of the door surface area.
Often wire glass is used in fire doors to prevent such glass breakage. Furthermore, no cracking, separation or other damage is permitted such as an opening between the wall and door.
Available Rating Labels
At the end of testing, the doors will end up with one of five ratings: the maximum 3 hour, 90 minutes, 60 minutes, 45 minutes, or 20 minute UL certified fire ratings.
While each door manufacturer must meet the UL criteria and are often part of a standards organization like the Steel Door Institute, hollow metal door ratings and tests are conducted by independent, internationally known labs.
When CDF Distributors receives hollow metal doors from the factory, these doors are already UL certified for 3hrs, but are only labeled with a plastic label.
Often though, local codes require that the steel door match a specific rating, thus as a UL certified labeling facility, CDF will apply the proper UL fire rating label upon customer request.