Cause and effect matrix for fire alarm systems
Preparing and updating Cause & Effect matrices to ensure system integration and emergency response.
The matrix defines exactly what must happen when each point activates. Without it systems behave as isolated islands: the alarm sounds, but ventilation does not stop, the lift does not return, and doors do not release.
We build the matrix as an explicit table: every cause — a zone smoke detector, waterflow in a sprinkler branch, a manual call point — against every required effect: shutting down air handling, recalling lifts to ground, releasing fire doors, starting smoke fans, notifying the control room.
The matrix serves twice: as the reference for whoever programmes the control panel, and as the commissioning test list. Any row that has not been physically tested is an unproven row, and we treat it as such.
For existing facilities that have been modified — space subdivision, added equipment, HVAC changes — we update the matrix and retest the affected rows. Undocumented modifications are the most common reason systems fail when actually needed.
- An explicit, testable cause-and-effect table
- Alarm integration with HVAC and lifts
- A commissioning test list
- Matrix updates after modifications
What is a cause and effect matrix?
A cause and effect matrix is a table linking every input to a fire alarm system — a detector, a manual call point, a signal from the suppression system — to every response that must follow in the other building systems. Rows are causes, columns are effects, and every marked cell is a documented engineering decision that is programmed into the fire alarm panel and tested at handover.
Common matrix mistakes
- A matrix written at design stage and never updated after site changes.
- Drastic actions, such as releasing suppression, tied to a single detector with no coincidence logic.
- Systems outside the alarm contractor's scope left out: lifts, air handlers, magnetic door holders.
- A matrix never physically tested, so it remains paperwork rather than proven logic.
A simplified cause and effect matrix example
| Cause ↓ / Effect → | Sound alarms | Shut down AHUs | Recall lifts | Release fire doors | Start smoke fans | Notify control room |
|---|---|---|---|---|---|---|
| Smoke detector — one zone | ●yes | ●yes | no | ●yes | ●yes | ●yes |
| Manual call point | ●yes | ●yes | ●yes | ●yes | ●yes | ●yes |
| Sprinkler flow switch | ●yes | ●yes | ●yes | ●yes | ●yes | ●yes |
| Lift lobby smoke detector | ●yes | no | ●yes | no | no | ●yes |
| Fire alarm panel fault | no | no | no | no | no | ●yes |
Illustrative example for a commercial building. A real matrix is built per project from its zones, systems and the reviewing authority's requirements.
Common questions about this service
Yes. It is required in the handover file for integrated alarm and suppression systems, and it is reviewed at final inspection to confirm correct response.