IEC 60529 defines, with a two-digit code, the protection an enclosure provides against solid objects and water. The most frequently confused point in specifications is the assumption that the code is a single durability score: in fact each digit corresponds to an INDEPENDENT test and when one rises the other does not rise with it.
Anatomy of the code
| Part | What it says |
|---|---|
| IP | The prefix defining the code itself (International Protection) |
| First digit (0–6) | Protection against solid foreign objects and access to hazardous parts |
| Second digit (0–9) | Protection against water |
| X | It means that NO TEST was carried out for that digit; it is not zero. IPX4 says that the dust side has not been declared |
| Additional letters | The standard defines additional letters for access protection and special cases |
Three common mistakes
- Assuming the second digit is cumulative: meeting a higher digit does not automatically mean that all lower digits are met; the standard states separately which digits cover which.
- Reading the IPX code as a zero: a test that was not carried out is not a failed test — but neither has it been declared.
- Taking the code as a guarantee for the product's whole life: the test is carried out with the enclosure in a particular state; gasket ageing, deformation after impact and covers opened by the user are outside the scope.
What should be written in the specification
Simply saying "make it IP67" is not enough. It must be stated in which configuration the enclosure is tested (covers closed, connectors mated, vents blocked or not), which surfaces are assessed, and which function is expected to work after the test. Without these three pieces of information, even a correctly performed test may not meet the buyer's expectations.
The test arrangements, durations and acceptance criteria for each digit are in the text of IEC 60529 and are under copyright; what is described here is the structure of the code and specification practice. Which digits to require for your product we determine together at the quotation stage.
What do the two digits separate?
In the protection class designation the two digits represent two separate risks, and they are independent of one another. The first digit describes protection against SOLID OBJECTS; its lower steps concern the hazard of access by the human body and its upper steps the ingress of dust. The second digit describes protection against WATER and progresses from dripping to pressurised water jets and from there to immersion.
Because the two are independent, one being high does not guarantee the other. An enclosure fully protected against dust may be protected against water only at the dripping level; conversely, an enclosure that withstands immersion may not be classified against the ingress of fine dust.
Why isn't the sequence always "increasing"?
This is the most misunderstood aspect of the water digit: a higher step does not automatically encompass all the steps below it. An enclosure designed to withstand pressurised water jets and one designed to withstand immersion use different physical solutions; the sealing gasket, pressure equalisation and drainage paths differ. If a product needs to declare that it meets both immersion and pressurised jet conditions, BOTH TESTS are carried out and the designation is written accordingly.
The class is not a measure of durability
- The test is carried out in a particular set-up, for a particular duration and under particular conditions; it does not show that the product will maintain the same protection over years.
- Gasket material ages, and ultraviolet and temperature cycling reduce its flexibility; the protection class does not cover that ageing.
- The test is carried out with clean water; exposure to detergents, fuel, salt water or chemicals requires separate assessment.
- Pressure washing, steam and high-temperature cleaning are a separate matter of classification; the pressurised water used in standard cleaning falls outside these classes.
- Condensation inside the enclosure is not the subject of the protection; moisture can condense inside a sealed box and damage the circuit.
Points to watch in the declaration
| Status | The right approach |
|---|---|
| If a digit has not been classified | An X is written in place of that digit; writing zero means "no protection" and would be incorrect information. |
| If the product is protected in a particular orientation | The test orientation and mounting direction are written together with the declaration; protection may differ in another orientation. |
| If there are additional conditions | Conditions such as covers closed and connectors fitted are part of the declaration and are stated in the user manual. |
| If user maintenance is required | The gasket replacement interval and the method of checking are written in the manual; the protection class assumes maintenance. |
Writing a protection class on the product label means that class has been demonstrated by testing. Declaring a class on the basis of design similarity is not a verifiable claim; when the enclosure geometry or gasket supplier changes, the test is repeated.