Hochiki Intrinsically Safe Conventional Smoke Detector, ATEX, Ivory SOC-E-IS

Overview

This Hochiki smoke detector is built for hazardous areas, where an explosive gas atmosphere may be present. It uses a high performance photoelectric chamber, which removes the need for ionisation detectors in the majority of applications.

It is meant for areas classified as hazardous, at Category 1 and all lower categories. The case is ivory; a white version is sold separately.

How it works

• Photoelectric sensing: photoelectric and optical mean the same thing here. Smoke entering the chamber scatters light on to a sensor.
• Baffle design: the baffle lets smoke into the chamber while keeping out ambient light.
• Drift compensation: dust slowly builds up in any chamber. The detector adjusts for it to stay at its optimum sensitivity, which reduces potential false alarms.

Where to use it

It is suitable for areas at Category 1 and all lower categories, within an ambient range of -20°C to +55°C. The IP42 case is meant for indoor ceilings.

As a rule, smoke detection is a poor fit for rooms with steam, heavy dust or fumes; a heat detector is the usual choice there.

What the figures mean in practice

• Ex ia IIC T5 Ga: ia is the highest level of intrinsic safety, IIC covers the most easily ignited gas group, T5 sets the maximum surface temperature class, and Ga is the equipment protection level for the most demanding zone.
• 120 µA when out of sensitivity: the current rises slightly when the red LED is flashing for cleaning, which matters for the circuit's current budget.

Installing it

In most installations, an intrinsically safe detector is powered through a certified barrier or isolator that sits in the safe area. Follow the system certification drawing for barrier type, cable limits and device count.

The detector mounts on the YBN-R/4(IS) base. Keep dust covers on during building work and remove them at handover.

Planning your system

Each head needs the Hochiki YBN-R/4(IS) intrinsically safe base. For a white ceiling, the white version is the SOC-E-IS(WHT) smoke detector.

Rooms with steam or fumes may suit heat detectors instead. The zone returns to a conventional panel from the range of commercial fire alarm panels.

The guide to commercial fire alarm systems explains zones and categories, and the wider Hochiki range covers bases, sounders and call points.

Standards and ratings explained

• EN 54-7: the standard for point smoke detectors that work by scattered light, transmitted light or ionisation.
• ATEX and IECEx: certification schemes for equipment used in explosive atmospheres. This detector holds Baseefa19ATEX0143X and IECEx BAS 19.0122X.