Two digits, one metre, thirty minutes: what IEC 60529 actually asks for

"IP67" is not an adjective. It is two test results.

The first digit covers dust (0–6). "6" means dust-tight — no dust inside at all, verified in a talcum-powder chamber at 2 kg/m³ with up to 2 kPa of negative pressure, for 8 hours. Any gap that passes dust will eventually pass moisture.

The second digit covers water (0–8). "7" means temporary immersion: the lowest point of the enclosure sits 1 m below the surface for 30 minutes, with the water within 5 K of the sample's temperature. Then the housing is opened and inspected. The verdict is not "it looks dry outside" — it is "no harmful ingress inside".

What IP67 does not cover

• Continuous submersion. That is IP68, which has no fixed depth or duration; it is agreed case by case.

• Steam. Vapour at 100 °C is a different failure mode. Steam cleaners and dishwasher interiors are not an IP67 conversation.

• Pressure washing. High-pressure jets belong to IPX6 and above.

• Ageing. A new sample that passes may not pass after a year of UV and thermal cycling.

The standard also does not require power. IEC 60529 evaluates the enclosure, so most labs test unpowered units. But seals fail while running: the display heats up, internal pressure rises, cold water drops it sharply, and the seal is pulled open. Testing powered is closer to the field — and harder to pass.

How we test

Our 1.28″ knob display goes into 1 m of water and stays lit for the full 30 minutes. On removal: normal display, no fogging behind the lens, no water inside the housing.

That is possible because the sealing is structural — lens bonded to the housing, a sealed shaft interface, a potted cable entry. Not conformal coating on the PCB, which only helps after water is already inside.