Hi All,

Currently operatoring a single tone alarm system. Alarm will set off continiously, soon as the zone is set off. If the system was a 2 tone system. The intermittent alarm would prepare all employees to ready for evacuation. Does site need to evacuate immediately with a 1 tone system or can it be a 5-10 second wait, incase it's a false alarm? 

BS 5839 allows for a fire alarm Time Delay System (TDS)

This allows for a Staff Search where trained individuals have a set time to check for false alarms 

Having the right fire detection kit is essential and training staff is paramount.  The cause and effect programs for the fire alarm panel may need to be changed and heat detectors are not usually suitable for TDS’

The activation of second head or any activation of a manual call point may trigger a full evacuation- its all down to risk assessment and what you are trying to achieve.

Your building needs to be able to accommodate a TDS. Compartment (fire resistant) floors can be useful, whereas large open voids between floors such as an accommodation staircase or escalators might make a TDS tricky to operate.

Some Staff Searches can be done silently, whereas others (especially in healthcare premises) use a two tone system like mentioned by the OP - an intermittent for ‘standby’ or continuous for ‘evacuate’. On larger premises a Voice Alarm System can provide scores of bespoke automatic messages in different parts of the building

Kate is right, you need a good reason for a TDS but there are plenty of them: 

1) Loss of production or productive time caused by an evacuation can cost a lot of cash. One site I have dealt with worked it out at almost half a million pounds per evacuation. In Schools, there can be a significant disruption to studying or exams. 

2) Safety: Evacuations bring with them a risk of injury. In healthcare, and where people are not familiar with the building, or where there is a sleeping risk, the risk associated with an evacuation can be significant

3) Commercial: Would you stay in a hotel again after being tipped out of bed at 03:00 in the rain? Turnover & profits can be effected by repeated unwanted fire signals Its not an easy system to introduce and its expensive as  a full risk assessment is required. New kit and training doesn’t come cheap and you may need several fire drills to help fine tune your systems

Please be careful. Your proposal of a fixed 5 to 10 second ‘wait’ is dangerous as it doesnt allow for a suitable search time. It is necessary to have a time where its not too long to put people at risk, but enough time to not rush the searching team into a poor decision. At the very least bring in a competent fire safety professional to give you some advice  ​​​​​​​Good luck