Mains Powered Interconnectable CO Detector - Kidde 4239HIR

Q.I purchased 4 alarms for my property recently via Safelinc's website. My electrician has installed them over the weekend.

However we have the following issue:

When you press the test button on the Carbon monoxide alarm the carbon monxide alarm goes off (but no alarm sound is heard on the other 3 connected smoke alarms).

This seems strange given that when you test any of the 3 smoke alarms, an alarm sound can be heard on the carbon monoxide alarm.

Is this meant to be like this?

The alarm models are:

1. Carbon Monoxide Firex 4985
2. Firex Ioisation 4881
3. Firex Ionisation 4870
4. Firex Optical 4985

A.The reason is the relevant British Standard which requires a different alarm sound for CO alarms in comparison to smoke alarms.

To achieve this, the CO alarm in question has a dual sound capability, meaning that

- if a smoke alarm is triggered or tested, the CO alarm detects that a smoke alarm has gone off and will activate one of its two internal sounders (sounding like a smoke alarm).

- if the CO alarm is tested or triggered, only the CO alarm sounds (sounding like a CO alarm). The smoke alarms are in this case not allowed to sound. As said above, this is a stipulation from BSI