The number in a fire door rating is the minutes of integrity the doorset achieved in a standard test, and the letter S after it means the door also restricts the passage of cold smoke. FD30 and FD60 cover almost everything in ordinary buildings, and the S is the part that matters most on an escape route.
What the number on fire rated doors means
FD30 is a doorset that maintained integrity for 30 minutes in a standard fire resistance test; FD60 for 60 minutes. It is a measure of the tested assembly, not of the leaf alone, and it is integrity rather than a promise that nothing gets hot. The rating is chosen to match the fire resistance required of the wall the door sits in, because a 60 minute wall with a 30 minute door is a 30 minute wall.
What the S adds
The S suffix means the doorset was also tested for leakage of cold smoke and carries smoke seals. Smoke kills more people than flame and moves through a building far ahead of it, so on doors protecting escape routes and in flat entrance doors the smoke performance is doing the real work. A door marked FD30 without the S has no tested cold smoke performance, whatever brush is fitted to it.
Where FD30 and FD60 fire doors are used
FD30 is the common domestic and light commercial rating: garage to house doors, doors onto protected stairways in houses, and many workplace compartment doors. FD60 appears where the compartment line requires an hour: some flat entrance doors, plant rooms, risers, and compartment walls in larger or higher risk buildings. The rating comes from the compartmentation strategy rather than from the door schedule.
Reading what you have
The label or plug on the top or hinge edge states the rating. A door with no identification cannot be assumed to be rated even if it is heavy, and weight is a poor guide: modern FD30 leaves can be lighter than old solid doors that have no rating at all. Where a survey cannot identify a door, the options are to test a sample destructively, to upgrade, or to replace.
Questions people ask about fire door fd30
What does FD30S mean?
A doorset tested to 30 minutes fire integrity that also restricts the passage of cold smoke and carries smoke seals. The S is what makes it suitable for escape route and flat entrance doors.
Is a heavy door a fire door?
Not necessarily. Weight is a poor indicator: modern rated leaves can be lighter than old unrated ones. The certification label or plug is the only reliable identification.
Can an FD30 door go in a 60 minute wall?
No. The door has to match the fire resistance required of the element it sits in, otherwise the compartment performs to the weakest part, which is the door.
What is a 60 minute fire rated door?
An FD60: a doorset tested to hold back fire for sixty minutes as a complete assembly, frame, seals and ironmongery included. The leaf alone does not carry the rating, which is why swapping hardware can end it.
Is a 60 minute fire door always an FD60?
That is what the designation means, but the rating belongs to the assembly rather than the leaf. A leaf marked FD60 in a frame it was never tested with, or with substituted ironmongery, is not a sixty minute doorset whatever the label says.