A self closing device is what makes a fire door a fire door in an occupied building, because a door that depends on somebody remembering is a door that will be open when it matters. The device has to close the leaf fully and drive the latch home from any opening angle, against whatever resistance the building offers, and it has to keep doing that for years with no attention.
Power size, which is the decision people get wrong
Closers are graded by power size, and the size needed depends on the leaf width and mass, on the seals the door has to compress, and on air pressure across the opening. Undersized closers are extremely common because a smaller size is easier to open, and the symptom is a door that closes from wide open and stalls in the last few degrees. That door has failed even though it looks and sounds like it is working.
The opening force problem
A closer strong enough to shut the door is sometimes too strong for some users to open, and disconnecting it is the wrong answer to a real problem. The engineered answers are a lighter certified doorset, a closer with variable power and adjustable backcheck, a free swing device, or a powered operator. Each of these keeps the fire function while fixing the access one.
Certification and compatibility
The closer is part of the tested assembly. It has to be within the doorset's certified hardware range and fitted to the manufacturer's template with the specified fixings, often with an intumescent pad behind the body and the arm. A closer bought on price and fitted with whatever screws came with it is outside the evidence, and the fixing into the leaf is a hole in the core.
Where an ordinary closer is not the answer
On a door that has to stand open for operational reasons, an ordinary closer will be defeated with a wedge within a week. The right product there is a hold open device or a free swing closer, both of which release the door on alarm activation. Specifying a stronger ordinary closer in that situation makes the wedging worse rather than better.
Questions people ask about automatic fire door closers
Does every fire door need a closer?
Most do. A door kept locked shut, such as a riser or a store, achieves the closed condition without one, and carries a keep locked shut sign instead.
Can an automatic door closer from a general supplier be used?
Only if it is within the doorset's certified range and fitted as the certification requires. Compatibility is a documented thing, not a judgement about whether it looks strong enough.
What is the single most common closer defect?
Failure to latch from a small opening angle. It is invisible unless somebody tests the door from a narrow angle, which is why the routine check says to do exactly that.