T3 Temporal Pattern

The  building code requires that new fire alarm systems use the T3 temporal pattern, an international standard, for fire alarm signaling. This pattern differs from the traditional constant alarm signal (fire bell) in that the signal is a programmed pulsed pattern.

The temporal pattern is intended to be consistent amongst buildings equipped with temporal alarm systems. Most existing constant alarm systems can be modified, and this pattern could be phased in when the systems require modification. The type of sound, producing the pattern, will vary when different types of signaling devices (such as gongs, speaker horns, etc.) are used.

The characteristic of the pattern is a three pulse phase followed by an off phase. The three pulses each consist of an on phase lasting for 0.5 ± 0.05 seconds followed by an off phase lasting for 0.5 ± 0.05 seconds sounded for 3 successive on periods and then followed by an off phase lasting for 1.5 ± 0.15 seconds. Additional details and commentary for the temporal pattern, can be found in Appendix Note A- of the BC Building Code.

To avoid confusion at the time of a fire alarm signal, notification and education should be provided, by the owner or owner’s authorized agent, as part of the fire safety plan, for the principal occupants of buildings, so they are aware and recognize their building’s fire alarm signal. The Fire Safety Plan shall be prepared in cooperation with the fire department.

For more information about this bulletin, contact the Office of the Fire Commissioner.