Intrinsically Safe Sounders: The Klaxon Sonos IS Range Explained
Intrinsically safe sounders and beacons are alarm devices built and certified for areas where a flammable gas, vapour or dust could be ignited by ordinary electrical equipment. Texecom has highlighted the Klaxon Sonos IS range, which holds ATEX and IECEx approval and, with a suitable barrier, can be used in Zones 0, 1, 2, 20, 21 and 22. Zenith does not currently list this range online, so please contact us for availability.
What is intrinsic safety?
Intrinsic safety is a protection method for electrical equipment used in potentially explosive atmospheres. Rather than relying on a heavy flameproof housing, the circuit keeps the available energy and surface temperature below the level that could ignite the surrounding gas or dust, in normal operation and under specified fault conditions.
A safety barrier on the safe side of the installation enforces that limit by restricting the voltage, current and power that can reach the hazardous-area cabling. It is either a shunt diode (Zener) barrier, which only protects the circuit when bonded to a dedicated high-integrity earth, or a galvanic isolator, which needs no such earth.
Where are intrinsically safe sounders required?
Hazardous areas are zoned by how often an explosive atmosphere is likely to be present: Zones 0, 1 and 2 for gases, vapours and mists, and Zones 20, 21 and 22 for combustible dusts.
| Zone | Atmosphere | How often the hazard is expected (general guide) |
|---|---|---|
| Zone 0 / Zone 20 | Gas or vapour / combustible dust | Present continuously, for long periods or frequently |
| Zone 1 / Zone 21 | Gas or vapour / combustible dust | Likely to occur occasionally in normal operation |
| Zone 2 / Zone 22 | Gas or vapour / combustible dust | Not likely in normal operation, and short-lived if it does occur |
Group I equipment is for mines endangered by firedamp or combustible dust, and Group II is for every other place where an explosive atmosphere can occur. Texecom lists the Sonos IS range under both.
Area classification should be carried out by a competent person and, in Great Britain, falls under the DSEAR regulations. The zone, the gas or dust group and the ignition temperature of the substances present then decide which alarm devices are acceptable, not guesswork.
The Klaxon Sonos IS range at a glance
Texecom offers Sonos IS as a sounder, a beacon or a combined sounder-beacon, approved "for use in potentially explosive atmospheres". Key details from its article and Klaxon's datasheets:
| Feature | Klaxon Sonos IS range |
|---|---|
| Approvals | ATEX and IECEx |
| Ex marking | Ex ia I Ma; Ex ia IIC T6 Ga; Ex ia IIIC T85°C Da |
| Standards | EN 60079-0:2012 + A11:2013 and EN 60079-11:2012 (both since superseded, so check the current certificate) |
| Fire standards | EN 54-3 for the sounder; no EN 54-23 listing seen for the beacon |
| Zones | 0, 1, 2, 20, 21 and 22 (Zones 0 and 20 need an [Ex ia] barrier) |
| Groups | Group I (mines) and Group II (other hazardous areas) |
| Barrier output limits | Uo 28 V, Io 93 mA, Po 660 mW |
| Sounder | 2-stage alarm with 32 selectable tones |
| Beacon | 9 SMT LEDs, 1Hz flash or static |
| Enclosure | IP66, flame retardant polycarbonate |
| Operating temperature | -40°C to +55°C |
| Wiring | Diode polarised; works with end-of-line resistors |
Installation points for installers
- Use a certified barrier or isolator. Klaxon requires every unit to be supplied through an approved barrier or isolator that stays within the output limits above and still meets Klaxon's minimum supply values.
- Check any existing barrier before reuse. Texecom says barriers already on site can be used, and it offers suitable ones alongside the range. First confirm the barrier's certified output against those limits, that its permitted capacitance and inductance cover the cable run, and that it is [Ex ia] for Zone 0 or 20.
- Plan the circuit. The devices are diode polarised and work with end-of-line resistors. Klaxon says monitoring needs a Zener barrier that allows reverse-polarity monitoring (it lists the MTL7778ac) and a fire panel compatible with intrinsically safe devices. The second stage needs a barrier with two diode return paths, or an extra intrinsically safe relay with an isolator. Allow for the voltage drop across the barrier at the 33 mA device load.
- Follow the hazardous-area standards. Klaxon asks for competent installers working to BS EN 60079-14 and 60079-25, with inspection to BS EN 60079-17. Check the Ex marking of each device and barrier against the area classification and keep certificates and loop checks with the system records. DSEAR also requires overall explosion safety to be verified by a competent person before a classified area is first used.
- Meet the conditions of use. Fixed installation only. Clean with a damp or antistatic cloth to avoid static build-up, use IP66 M20 glands and plug any opened entry that is not in use.
Can you buy the Klaxon Sonos range from Zenith?
Zenith does not currently list Klaxon Sonos intrinsically safe sounders or beacons on our website. If your project includes a classified hazardous area, contact our team for availability and we will look into sourcing options with you.
If the non-hazardous parts of a site run on a Fike Twinflex 2-wire system, we stock Twinflex devices such as the Fike Twinflex sounder and the Fike Twinflex Flashpoint LED beacon. They are designed for Twinflex panels, and neither is intrinsically safe or ATEX-approved, so both belong outside classified zones.
You can also browse our full fire alarm range, including fire alarm panels and kits and fire alarm accessories. For security systems, see our Texecom range of Premier Elite panels, Ricochet wireless devices and Odyssey sounders.
Frequently asked questions
What is an intrinsically safe sounder?
A sounder whose electrical energy and heat stay below the level needed to ignite a flammable gas, vapour or dust, with a barrier on the safe side limiting the energy reaching it.
Which zones is the Klaxon Sonos IS range suitable for?
Texecom states the range suits Zones 0, 1, 2, 20, 21 and 22, with ATEX and IECEx approval for Group I (mines) and Group II (other hazardous areas). Use in Zone 0 or 20 needs an [Ex ia] barrier or isolator.
Do intrinsically safe beacons need a safety barrier?
Yes. Klaxon says Sonos IS devices must be supplied through an approved shunt diode (Zener) barrier or galvanic isolator, which limits the energy reaching the hazardous area. A Zener barrier also needs a dedicated intrinsically safe earth; a galvanic isolator does not.
Does Zenith stock the Klaxon Sonos range?
Not online at present. Contact Zenith Security Co for availability, or browse our Fike Twinflex fire alarm devices for use in non-hazardous areas.
Source: product details are taken from Texecom's article The Klaxon Sonos Intrinsically Safe Range, with the Ex marking, barrier limits and installation conditions from Klaxon's datasheets and manual. Always check the manufacturer's current certification before specifying equipment for a hazardous area.
