Detection is a sensing problem before it is a wiring problem. Smoke, heat, flame and gas all announce a fire differently, at different speeds, and each sensor is fooled by a different everyday event. Choosing wrongly does not usually produce a system that misses fires; it produces a system that cries wolf until somebody disables it, which amounts to the same thing.
Smoke detection
Optical detectors sense light scattered by smoke particles and respond well to the smouldering fires that kill people at night. Ionisation types respond faster to fast flaming fires with small particles. Optical is the general purpose choice in most buildings. Both are fooled by steam, dust and aerosols, which is why siting near bathrooms, loading bays and kitchens is a design decision rather than a convenience.
Heat detection
Heat detectors respond to a fixed temperature, a rate of temperature rise, or both. They are slower than smoke detection by design, so they are used where smoke detection would be unusable rather than where it would be better: kitchens, plant rooms, dusty workshops and garages. Using them to solve a false alarm problem elsewhere is trading warning time for quiet.
Aspirating, beam and flame detection
Aspirating systems draw air through a pipe network to a central sensor and can detect at very low smoke concentrations, which suits high value spaces and places where access to a ceiling is difficult. Optical beam detectors cover large open volumes such as atria and warehouses with one path. Flame detectors watch for the radiation signature of flame and suit large open areas with a fast fire risk and no smoke path to a ceiling.
Mixing types of fire detection systems in one building
Real buildings need several. The skill is in matching the detector to the space, and the tell of a good design is a schedule that says which type goes where and why. A design that specifies one detector type throughout a building with a kitchen, a plant room and an office is either very simple or has not been thought about, and the false alarm log will tell you which within a year.
Fire prevention systems and fire prevention equipment: the two halves people conflate
Prevention and protection answer different questions and are bought from different budgets. Prevention removes or controls the ignition sources and the fuel: electrical maintenance, hot work permits, waste management, smoking arrangements, storage away from the building line, charging arrangements for lithium batteries. Protection deals with a fire that has started: detection, warning, escape routes, compartmentation, extinguishers, suppression. An assessment that lists detection and extinguishers and says nothing about the bin store against the wall or the pallet stack in the yard has covered the second half only, and the insurer will usually notice before the officer does.
Questions people ask about fire detection systems
What is the difference between optical and ionisation detectors?
Optical responds better to smouldering fires with larger smoke particles, ionisation to fast flaming fires with smaller ones. Optical is the general purpose choice for most buildings today.
Which detector should go in a kitchen?
Normally a heat detector, because cooking will set off a smoke detector often enough that somebody removes it. That is a deliberate trade of sensitivity for a system that stays in service.
Are aspirating systems worth the cost?
Where very early detection matters or ceilings are effectively unreachable, yes. In an ordinary office they are expensive for what they add. It is a question about the space rather than about the technology.
Where do fire extinguisher systems fit beside detection?
They are the manual layer and the detection is the automatic one, and the assessment should say what each is there for. Detection and warning buy the time to get out; extinguishers give a trained person the option of dealing with something small on the way. The failure mode is treating a wall of cylinders as the fire strategy: an unmanned building at night is protected by detection, compartmentation and the brigade, not by an extinguisher nobody is there to use. Where the risk genuinely needs an automatic response at the source, that is a suppression system and a different design exercise.
Is a fire alarm system wireless installation as good as a wired one?
For many buildings yes, and it is often the only proportionate answer in a listed or occupied building where cabling would mean chasing walls. The system is designed to the same standard and the differences are practical: battery life and the maintenance that goes with it, the survey to confirm signal paths between devices, and a limit on how large a single system can sensibly get. Ask for the site survey rather than a product sheet, ask what the battery replacement programme costs over ten years, and compare that with the cabling it saves.