What Does Intrinsically Safe Mean?

Intrinsically safe describes electrical equipment designed so that it cannot ignite a flammable atmosphere, because the energy available in its circuits, as a spark or as heat, is kept below the level needed for ignition. The safety is built into the circuit itself rather than provided by a strong box around it, which is where the word intrinsic comes from.

The design must stay safe not only in normal use but also when components fail, wires break or terminals short. How many faults it must survive sets its level of protection. Intrinsic safety is one of several protection concepts recognised under ATEX, IECEx and the North American codes, and the international standard for it is IEC 60079-11; in the US the equivalent is UL 913.

Because the energy limits are tight, intrinsic safety suits low-power equipment: pressure and temperature transmitters, gas detectors, radios, phones, scanners and some tablets. A full-size panel PC usually needs too much power, so it uses a different method.

Intrinsic safety is assessed as a system, not just a device. A typical loop has four parts.

Intrinsic safety prevents ignition by limiting energy. The other main methods contain, exclude or avoid ignition instead. The table sets them side by side.

The most searched comparison is intrinsically safe vs explosion proof. Explosion-proof, or flameproof, equipment assumes the gas will get inside and that ignition may happen, and relies on a heavy enclosure to stop the flame escaping. Intrinsically safe equipment assumes the gas is everywhere and makes ignition impossible. Explosion-proof designs handle high power but are heavy and must stay sealed; intrinsically safe designs are light and can be opened or worked on live, but only at low power.

Look at the marking, not the brochure. An intrinsically safe device carries a hazardous area marking that includes ia, ib or ic, such as Ex ia IIC T4 Ga, together with an ATEX, IECEx or UKCA certificate number, or in North America an intrinsically safe listing to UL 913 for a stated class, division and group. The level decides where it can go: ia suits Zone 0, ib Zone 1 and ic Zone 2 only, as our ATEX zones explainer sets out. A product described as “intrinsically safe” with no marking or certificate is not.

Level ic is worth noting because many rugged mobile devices use it. Our rugged tablets include a 10.1 inch ATEX and IECEx Zone 2 model marked Ex ic IIC T4 Gc, and our rugged handheld computers include a Zone 2 version with Ex ic protection. Both are certified for Zone 2, not Zone 1. Fixed screens are a different case: our hazardous area panel PCs cover Zone 2 and Class I, Division 2 using methods suited to their higher power.

Intrinsic safety is common wherever instruments and people work inside zoned areas: refineries, offshore platforms, gas terminals and pipelines in oil and gas, and also chemical and pharmaceutical plants, distilleries, grain and flour handling, mining and wastewater treatment. Typical users are instrument technicians, inspectors and operators carrying radios, gas detectors, thermal cameras, phones, scanners and tablets.

The limits are worth planning for. Power is low, typically a few watts at most per circuit, so screens are dimmer and processors slower than on standard devices. Batteries, chargers and accessories are part of the certification, and certificates often say batteries may only be changed or charged in a safe area.

We supply hazardous area mobile and fixed systems with the manufacturer’s certification intact, and as standard we integrate and validate each one within that certified configuration before it ships.