This whole month has been about scary movies, haunted houses and a lot of sweet treats. It’s fun to pretend ghouls and goblins are real and imagining what we would do to protect ourselves. But let’s be honest, the scariest things in life aren’t the make-believe monsters, but the real-life things we encounter that can put our lives in danger. For instance, something that is truly scary is poor clearance dimensions around the perimeter of the door in the closed position!
One of the top deficiencies found in fire door inspections is “poor clearance dimensions”. Too often gaps around the perimeter of a fire door will be greater than the gap allowances for fire doors acceptable by NFPA 80. Fire uses oxygen to burn, and a large fire in a closed room will begin to consume all the oxygen in that area, creating a vacuum of negative pressure near the base of the fire. The heat from the burning materials creates intense positive pressure near the ceiling of the room. This is where the fire door gaps becomes important. With properly sealed and fire resistant gaps, the fire will not have a constant supply of fresh oxygen to burn, and will burn smaller or even die out on its own.
If the gaps are too big, the negative pressure will cause fresh oxygen to be sucked into the room with the fire, feeding it and allowing it to grow bigger and hotter. This will also make the positive pressure stronger, forcing the hot air and smoke out of the higher fire door gaps and into areas that are supposed to be safe from the fire. This hot air and smoke can actually be able to ignite combustibles, creating a fire on both sides of the closed door. So, then what are the acceptable gap allowances for fire doors that won’t allow fire and smoke to pass through?
Swinging Doors with Builders Hardware
Gap Allowances for Fire Doors made of Wood:
- Clearance for under the bottom of the door maximum is 3/4”
- Clearance between door and frame is 1/8”
- Clearance for meeting edges for a pair of doors is 1/8”
Gap Allowances for Fire Doors made of Steel:
- Clearance for under the bottom of the door maximum is 3/4”
- Clearance between door and frame is 1/8”, +/- 1/16”
- Clearance for meeting edges for a pair of doors is 1/8”, +/- 1/16”
Vertically Sliding Fire Doors
- Clearance between the door and the wall when the door is closed is 3/8 in.
Fire door gaps may seem like a small issue to take care of, but even small issues could cause a lot of harm and damage if not taken care of properly. It’s important for the clearance around the perimeter of the fire door to be within the appropriate limits to help prevent the spread of fire and smoke. However, if a fire door does have a gap larger than what is acceptable by NFPA, then a fire rated seal will be used to help close the gap. Gaps can be sealed with an intumescent strip that when exposed to heat will expand, a neoprene weathering strip, or gaskets to help prevent the passage of smoke.
