At one time or another, most of us have noticed the fire rating on a door, though not all of them have one. Perhaps, at the moment, you’re in the market for a door and have either been tasked to find one with a sufficient fire door rating or are just curious to know whether or not it’s important. No matter what the reason, fire door ratings are fairly easy to understand, though nonetheless important.
What Is a Fire Door?
Put in simplest terms, a fire door is simply one that has a rating signifying how effective it is against fire. As such, most fire doors are designed specifically for use in the case of a fire breaking out. By providing a passive structure the fire can’t get through, it’s believed a fire door can help save lives and property.
Fire doors can be made from a wide range of materials, though they must all be fire-resistant, obviously. Typically, these materials include vermiculite and steel gypsum. Their edges are usually sealed in a fire-rated seal of some sort as well. These seals are designed to expand hundreds of times over when heated to ensure that fire is unable to get around the door by sucking oxygen through cracks.
Despite how heavy-duty these doors sound, many blend right in to modern buildings. For example, the metal doors with push bars in their center are generally fire doors.
Testing Fire Doors
Fire doors are actually given their ratings by a unified body called the NFPA (National Fire Protection Association). Their methodology is known as the Standard Test Methods for Fire Door Assemblies. Any door that gets tested by the NFPA is subjected to a certain amount of fire. The amount of time it is exposed to fire is then measured in 15-minute intervals (15, 30, 45, full hour, etc.)
Before the test—which is officially known as NFPA 252—begins, the door in question needs to be completely put together. Most doors need to be built before they’re actually installed, but the NFPA 252 is only interested in the finished product.
A furnace is used for the test so that the fire is brought up to the desired temperature before applying it to the door. When it reaches the desired temperature, the fire is then focused on one side of the door. The fire will continue to be applied to the door being tested until a duration that meets the rating being sought out by the manufacturer or the door gives out.
The Conclusion of the Test
When either the door passes by making it the rating the manufacturer was after, or it fails by falling short, the test is finished with a hose that applies a stream for 20 minutes straight. The goal is to obviously put out the fire, but to also do it in a way that the door can be studied later to truly discern its overall integrity.
The Fire Rating
So what does the fire rating actually mean? First, it’s not a consistent measurement between doors, because a model is most likely being assessed for a different building. Each building generally has its own fire a code, meaning each fire door has something different to measure up to.
Adding to the ambiguity is the fire used in the test. Recall that it was essentially prepped to hit a certain temperature. It’s continuously prepped throughout the test so that the fire will act as realistic as possible by rising in temperature. However, real building fires don’t act like this, meaning fire can rise in temperature sporadically. So the fire test just described is simply a best attempt at recreating realistic scenarios.
Fortunately, fire doors work more often than not. However, know that you can’t simply compare one to the other by assuming that their fire door ratings mean the same thing.