Active fire protection does something when a fire starts: an alarm sounds, a sprinkler discharges, a damper closes. Passive fire protection does nothing at all, ever, and that is the point. It is built into the structure and works by simply being there, which is also why it is the half nobody inspects until something goes wrong.
What is passive fire protection, and what counts as passive
Compartment walls and floors. Fire doors and their seals. Fire stopping at service penetrations. Cavity barriers in voids and external walls. Fire resisting ductwork and dampers where they are not actuated. Structural fire protection such as intumescent coatings and boarding to steelwork. Fire resisting glazing. All of it is construction rather than equipment, and none of it has a test button.
What counts as active, from smoke alarm systems to sprinklers
Detection and alarm systems. Sprinklers, water mist and gaseous suppression. Smoke control and automatic opening vents. Fire dampers that close on a signal. Lifts designed for firefighting. These have moving parts, power supplies and a maintenance regime, which is why buildings maintain them: there is something to service and somebody selling the service.
Why passive protection is neglected
It is hidden above ceilings, inside risers and behind walls. It is damaged by other trades doing unrelated work, months or years after handover. There is no alarm when it fails. And there is no annual visit that would notice. A building can pass every alarm, extinguisher and emergency lighting inspection for a decade while its compartmentation has been quietly destroyed by cabling contractors.
Structural protection and treated timber
Steel loses strength as it heats, so structural steelwork is protected with intumescent coatings, boards or sprays to a specified thickness for a specified period. Timber can be treated with flame retardants to reduce surface spread of flame, which is a different property from fire resistance and does not make treated timber a fire resisting element. Reading which property a product claims is the whole skill here.
Questions people ask about active and passive fire protection
What is the difference between active and passive fire protection?
Active protection does something when a fire starts, such as sounding, discharging or closing. Passive protection is built into the structure and works by being there: walls, doors, seals and fire stopping.
What are examples of passive fire protection?
Compartment walls and floors, fire doors and seals, fire stopping at penetrations, cavity barriers, fire resisting glazing and structural protection to steelwork.
Does fire retardant treatment make timber fire resisting?
No. Flame retardant treatment reduces surface spread of flame, which is a different property from fire resistance. Treated timber is not a fire resisting element.
What counts as passive fire protection systems in a building?
Compartment walls and floors, fire doors and their ironmongery, the sealing where pipes and cables pass through a compartment line, dampers in ductwork, and any structural protection applied to steel. They work by being built correctly and left alone, which is why they are the part nobody notices has been breached.
Is fire resistant paint the same as an intumescent coating?
Usually it is the same product under a looser name: a coating that swells when heated to insulate the steel or timber underneath. It carries a rating only in the tested system, at the tested thickness, on the tested substrate, which is why the applicator's record of dry film thickness matters more than the tin.