Hushing Interlinked Smoke Alarms

Interlinked smoke alarms are becoming more and more popular as they quickly alert you to the event of a fire across larger houses, where there is a risk that you might not hear an alarm going off in the kitchen when you are, for example, in a bedroom upstairs.

Whether connected to each other with wire or wirelessly interlinked through radio frequency, interlinked smoke alarms allow you to connect multiple units – including different types of detectors – which will all sound at the same time when a single alarm detects a potential fire. The heat alarm in the kitchen, the ionisation alarm in your home office, and the specialist strobe and vibration alarm in your elderly parents’ bedroom, for example, will all go off at the same time, if just one alarm is triggered by fire.

Most of us are familiar with the test button on smoke alarms which allows residents to test their alarms regularly, to ensure the components are working and the power supply, whether battery or mains power, is working. On top of this, however, many alarms have a “hush” button which allows you to silence an alarm that has gone off, for example, due to burnt toast.

So how do hush buttons work when you have several interlinked alarms?

It’s easy to assume that, as they are all connected, hushing one alarm will silence all of them, but it is equally logical that only the unit on which you pressed the hush button should be silenced – after all, you don’t want people to assume it was a false alarm if there really is a fire raging downstairs.

Interestingly, not all interconnecting smoke alarms hush in the same way. Here is an overview explaining the different approaches employed by the three main smoke alarm manufacturers in the UK.

Kidde Slick Wireless Smoke and Heat AlarmsFor Kidde smoke alarms, the originating alarm (the unit which detected a potential fire and triggered all of your units) will have its warning light flash faster than all other units while the alarm is sounding – enabling you to identify the smoke alarm that caused the alarm. Pressing the hush button on ANY unit will silence the ENTIRE network.

Ei160e Series Smoke and Heat AlarmsIf you have interlinking Ei Electronics smoke alarms, only the originating unit’s hush button will be able to silence the ENTIRE network. The other units in the circuit can be individually silenced. To identify the originating unit you need to look for the alarm whose warning light is flashing every second, compared to every 40 or so seconds on the other units.

FireAngel WST600 Series Radio-Interlinked Smoke and Heat AlarmsFireAngel smoke alarms, however, deploy an improved silencing protocol. If you hush the originating smoke alarm then, as with the other brands, ALL connected units will be silenced. However, if you hush any other unit, the ORIGINATING alarm will continue to sound but ALL OTHER units will be silenced. This allows you to quickly identify the originating alarm which is very helpful both in case of a false alarm or a real emergency.

If you require support selecting the best smoke alarm system for yourself, please contact the friendly Safelincs support team either by emailing support@safelincs.co.uk or by ringing 0800 612 6537

Smoke Alarms versus Fire Alarms in HMOs

flatsDefined under BS 5839: Pt. 6 a house of multiple occupancy (HMO) is “a house that is occupied by persons who do not form a single household.” These are typically large houses that have been converted into flats or bedsits. Many of our customers ask what type of smoke alarm system is suitable for this type of property. According to the British Standard, the recommendations are as follows:

For one or two storey HMOs where the individual floor area is no more than 200sqm, a Grade D, category LD3 smoke alarm system should be installed.  Grade D refers to mains powered smoke and heat alarms with a built-in back up battery power supply, and the alarms can be interconnected either by wire or by radio signal. That means that fire alarm panels are not required. Ei Electronics and Kidde offer both RF and wired mains powered alarm systems as well as a range of accessories that can help you to test, locate and hush alarms easily.

Category LD3 (level of coverage) is the minimum requirement and defines where alarms should be installed. LD3 requires smoke alarms in all circulation spaces that form part of the escape routes from the dwelling, i.e. hallways and landings. If justified during a fire risk assessment, the level of cover may be increased to LD2 which requires smoke or heat alarms to be installed in specified high fire risk rooms and areas. Dependent on the specifier, this can include living rooms, kitchens and possibly bedrooms.

For Grade D system it is becoming more and more acceptable (especially if retrofitted) to install radio-interlinked smoke and heat alarms with 10 year sealed batteries rather than mains powered smoke and heat alarms. This saves the cost for the electrician and systems like this can be installed very quickly. We still recommend that you ask for confirmation by building control or the relevant council department before installing these systems.

For HMOs of 3 storeys or higher, there are two options available.  The first is to have Grade A fire alarm system installed throughout the building.  Grade A consists of a conventional or addressable fire alarm panel, and then fire alarm detectors, call points, sounders and beacons are specified according to the layout and requirements of the property.  The second option is to have a mixed system.  This would comprise of  Grade D, category LD3 in the individual dwellings (see above) and a separate Grade A system in the communal areas.  Again, the category of cover in the individual dwellings can be upped to LD2 if needed.  Both of these options have pros and cons depending on the requirements and the owner’s access to each of the dwellings.  A mixed system appears to have become the preference, as it is likely to reduce the impact of nuisance alarms from individual flats on other occupants.

For additional guidance, please visit our Smoke Alarm Help and Information, BS 5839-6 and BS 5839-1 summary pages.