IP66 vs IP67: what the numbers really mean for outdoor LED luminaires

The two digits

The first digit covers solids, the second covers liquids. Both IP66 and IP67 are fully dust-tight (6). The difference is entirely in the second digit.

• IPx6 — protected against powerful water jets from any direction. Think driven rain, hose wash-down, storm conditions.
• IPx7 — protected against temporary immersion up to 1 m for 30 minutes. Think flooding, or a fitting mounted low in a wash-down area.

Which one do you actually need?

For almost every outdoor floodlight, street light and high bay, IP66 is sufficient and cheaper. IP67 earns its premium in three cases: fittings mounted below 300 mm from the ground, areas that flood seasonally, and food or chemical plants with regular hose-down or immersion risk.

The part datasheets do not say

IP is measured on a new fitting. What decides ten-year performance is the gasket: its material, its compression and whether the housing has a breather to equalise pressure. A fitting that cycles temperature daily without a breather will pump moisture inside regardless of its IP number.

That is why PangDun carries a breather valve as standard and why we test gaskets after 1,000 hours of thermal cycling, not only on the day of assembly.