Are ionisation smoke alarms still suitable in corridors?

[Guest John]

Hello, we have been asked to replace smoke alarms in the communal corridors of apartment buildings. The current ones fitted are ionisation alarms, is this still considered the most suitable for this type of area. Thank you

[Tom Sutton]

Point Smoke Detectors:

 

1 Ionisation chamber Smoke Detectors which are very sensitive to smoke with small particles i.e. fresh cellulosic smoke and the source of almost invisible smoke one gets with burning paper and spirit. They are relatively insensitive to smoke with large particles for example, smoke produced by burning plastics or stale smoke.

 

2 Optical Smoke Detectors are sensitive to optically dense smoke i.e. smoke with large particles and they are relatively insensitive to optically thin smoke.

 

3. CO fire detectors detect the CO from a deep seated smouldering fire and give an alarm, not to be confused with CO detectors that give an alarm when the CO reaches dangerous toxic levels.

 

4. Multi sensor detectors which are detectors that combine a number of sensors and give the alarm when all reach a positive state.

 

Some countries i.e.: Italy, Japan, Qatar only uses Optical Smoke Detectors and within parts of the Middle and Far East, only Ionisation Detectors are used. Within the UK systems can comprise of a mixture of the two. Optical Detectors are normally used on escape routes such as corridors and stairwells. Ionisation Smoke Detectors are normally fitted within office and other general areas.

 

All fires will produce elements that can be detected by all three detectors but in my experience domestic fires produce a great deal of thick smoke which is best suited to optical detector and as the principle aim is to warn the occupants before the escape corridors become untenable, also they are also less subject to false alarms.

 

Using multi sensor detectors with ionisation and optical sensors may be a better solution, depending on false alarms but it may not be feasible in your situation.