An Ordinary Light Fitting in a Gas Store Is an Ignition Source

Walk into many LPG cylinder stores, fuel pump rooms or solvent stores and the lights, switches and sockets look exactly like the ones in the office. Sometimes that is because they were installed that way. More often the original explosion-protected fittings were replaced, one at a time, with whatever was on the shelf. Either way the result is the same: an ordinary electrical device sitting in a space where flammable gas or vapour can collect, waiting for the day there is a leak.

What hazardous area classification actually decides

Hazardous area classification is the assessment of where, how often and for how long an explosive atmosphere could be present. Under IEC 60079-10-1, areas where gas or vapour may be present are divided into three zones:

• Zone 0: an explosive atmosphere is present continuously or for long periods, for example inside a tank above the liquid.
• Zone 1: an explosive atmosphere is likely to occur occasionally in normal operation, such as around filling points and vents.
• Zone 2: an explosive atmosphere is not expected in normal operation and, if it occurs, lasts only a short time, typically around flanges, valves and pump seals.

Facilities designed to North American practice use the Class and Division system of NFPA 70 Article 500, while API RP 500 and API RP 505 give detailed guidance for petroleum facilities. Combustible dust has its own zones, 20, 21 and 22, under IEC 60079-10-2. Whichever system applies, the classification drawing is what tells the electrician which equipment may be installed where.

Reading the Ex marking

Equipment intended for a hazardous area carries a marking that must match both the zone and the substance. The protection concept shows how ignition is prevented: Ex d flameproof enclosures contain an internal explosion, Ex e increased safety prevents sparks and hot spots, and Ex i intrinsic safety limits the energy in the circuit. The gas group, IIA, IIB or IIC, and the temperature class, T1 to T6, must also suit the gas or vapour present. A fitting certified only for Zone 2 is not acceptable in Zone 1, and the wrong temperature class can turn a hot surface into an ignition source on its own.

Where protection is lost in practice

Explosion protection is rarely defeated by the original design. It is lost gradually, during operation and maintenance:

• A failed Ex light or junction box replaced with a standard industrial one.
• Cable glands that do not match the enclosure certification, or unused entries left open instead of sealed with certified blanking plugs.
• Flameproof joints painted over, corroded or missing bolts.
• New pumps, vents or drains added without revisiting the classification drawing.
• Portable tools, extension leads and mobile phones taken into Zone 1 without a hot work permit and gas test.

Inspection that keeps the zones honest

IEC 60079-14 covers the selection and installation of equipment in hazardous areas, and IEC 60079-17 sets out how it should be inspected and maintained, from the initial inspection through periodic visual, close and detailed inspections. A sound programme starts with a current classification drawing, an equipment register that records the certification of every item, and inspectors who can recognise when a fitting no longer matches its zone.

EnvironmSafe's evaluation teams review area classification for LPG installations, fuel systems and process plants, inspect explosion-protected electrical equipment in the field, and deliver clear remedial lists that maintenance teams can act on. For clients across Yemen and the Middle East, this sits alongside our LPG, fire protection and electrical evaluations, so the whole ignition picture is assessed together rather than one system at a time.