It is listed against a life-safety objective rather than a property-protection one.

A commercial head is designed to control a fire and limit damage to the building.

A residential head is designed to keep the room of origin survivable long enough for occupants to get out.

That drives fast response, a wall-wetting spray pattern and larger listed coverage areas.

The two are listed under different criteria and are not interchangeable.

Using a commercial head in a residential design, or the reverse, invalidates the design.

Because flashover in a domestic room is driven by heat radiating from the upper walls and ceiling.

Cooling those surfaces delays the point at which everything in the room ignites at once.

A pattern that only wets the floor does less to prevent that.

Residential heads are tested against room-scale fire scenarios rather than component-level criteria alone.

That is also why their listed coverage and positioning rules differ.

Obstructions such as high furniture and ceiling fans matter for the same reason.

Many are designed to, which is what makes retrofitting achievable - but the supply has to be measured.

Flow and pressure at the property must be tested rather than assumed from the mains size.

A supply that is fine for taps and showers may not deliver a sprinkler design flow.

Where the supply is inadequate, a tank and pump arrangement is used instead.

Shared supplies, long service runs and older mains are the common causes of shortfall.

The test is a standard part of the design process and should be done before the system is specified.

It varies enormously by market - some jurisdictions mandate them in specific building types or above certain heights, others do not require them at all.

The variation here is larger than in almost any other part of fire protection.

Requirements have generally moved towards wider application over time.

Height, building type, occupancy and whether the work is new build or refurbishment all feature in different regimes.

Insurers sometimes require them where regulation does not.

The applicable requirement should be established locally rather than assumed from practice elsewhere.

Far less than a fire, and far less than fire service hoses, because only the head over the fire operates.

A single residential sprinkler discharges a small fraction of what firefighting hoses deliver.

Early operation also means a much smaller fire to extinguish.

The perception of widespread discharge comes from film and television rather than from how the technology works.

Accidental discharge from damage or freezing is possible and is the main real water risk.

Guards, correct temperature ratings and protection from freezing address that.

Yes, and concealed residential heads are widely used because the appearance objection is strongest in homes.

A flush cover plate matching the ceiling leaves only a small disc visible.

As with any concealed head, the plate is part of the listed assembly and cannot be substituted.

Painting a plate during redecoration is the recurring risk in a domestic setting.

Sidewall residential heads are also common where ceiling access is limited.

Factory-finished plates in a range of colours avoid any need to paint.

Less than a commercial system, but not none - and the requirements are set locally.

Typical duties include checking the water supply, checking valves are open and confirming heads are unobstructed and unpainted.

Occupants need to know not to hang anything from a sprinkler or paint a cover plate.

Systems with tanks and pumps require more, including periodic pump testing.

Handover information for occupants is part of the installation in most regimes.

Intervals, responsibilities and record-keeping differ by jurisdiction and by tenure.