Specifying an enclosure without understanding its ingress rating is how equipment ends up failing in a place it was supposed to survive. IP ratings explained properly come down to a simple question with expensive consequences if answered wrong: what exactly is this housing protected against, and under what conditions. The code that answers it is precise, internationally standardized, and routinely misread, which is why a washdown-rated panel sometimes floods and an immersion-rated one sometimes fails under a pressure jet.
What Is an IP Rating?
An IP rating, from Ingress Protection, classifies how thoroughly an enclosure resists the entry of solid objects and water. The system is defined by IEC 60529, the international standard covering degrees of protection provided by enclosures for electrical equipment. The standard establishes the classification and test framework behind the IP Code, helping ensure that ratings are interpreted consistently across applications.
For electrical equipment, an IP rating is a defined technical classification rather than a general claim of ruggedness, and it can form an important part of determining whether equipment is suitable for a particular operating environment. Therating carries weight only because it corresponds to a defined laboratory test, not to a manufacturer's general claim of ruggedness. That traceability is what lets a specifier trust an IP number on a datasheet.
How to Read an IP Code
The code follows a fixed format: the letters IP followed by two digits, occasionally with added letters for special cases. The first digit describes protection against solid objects, from fingers down to fine dust. The second digit describes protection against water, from vertical drips up to sustained immersion. A rating of IP67, for example, declares complete protection against dust ingress and resistance to temporary immersion. Where a digit is replaced by an X, that characteristic simply has not been rated, which is not the same as scoring zero. Reading the two digits independently is the first step to specifying correctly.
First Digit: Protection Against Dust and Solid Objects
The solids scale runs from 0 to 6. The lower values cover protection against large objects and tools, relevant mostly to accessibility and touch safety. The distinction that matters in industrial specification sits at the top of the scale, between 5 and 6. An IP5X enclosure is dust-protected: dust may enter, but not in a quantity that interferes with operation. An IP6X enclosure is dust-tight, admitting no dust at all. The gap between dust-protected and dust-tight decides whether an enclosure survives in a cement plant, a grain facility, or any environment where airborne particulate is constant. Choosing 5 where 6 is required is a common and costly error.
Second Digit: Protection Against Water
The water scale runs from 0 to 9, and it is not a simple ladder of severity. Levels up to 6 describe increasing resistance to sprays and pressurized jets, from light drips through heavy seas and powerful jets. Levels 7 and 8 describe immersion: temporary submersion for 7, continuous submersion under defined conditions for 8. The critical point that specifiers miss is that immersion protection does not automatically include jet protection. An enclosure rated for immersion may still admit water under a high-pressure jet, because the two tests simulate different physical stresses. Reading the second digit for the actual threat, spray or submersion, is what prevents a mismatched specification.
IP65, IP67 and IP68 Compared
The three ratings most often specified in industrial work illustrate why higher is not always better. IP65 is dust-tight and protected against water jets from any direction, the right choice for outdoor equipment and washdown environments where surfaces are sprayed but never submerged. IP67 is dust-tight and protected against temporary immersion, suited to equipment that may be briefly flooded or dropped in water IP68 is dust-tight and provides protection against continuous immersion under conditions specified for the particular equipment, making it relevant to applications where prolonged water exposure or submersion may occur. The trap is treating these as a simple ranking. An IP68 enclosure optimized for static immersion can underperform an IP65 one under a directed pressure jet, because immersion and jet resistance are tested against different conditions.For washdown environments, a rating specifically covering the relevant jet pressure, water temperature and cleaning conditions may be more appropriate than relying solely on an immersion rating such as IP68.
How to Preserve an IP Rating: The Role of Industrial Cable Glands
An enclosure holds its rating only as well as its weakest opening, and the weakest opening is almost always where cables enter. A perfectly rated housing loses its integrity at an unsealed or wrongly specified entry point, which is why the gland carries the rating as much as the enclosure does. CEMBRE’s range of industrial cable glands includes options in nylon, brass and stainless steel. Material selection depends on the operating environment and application requirements: nylon is commonly used for indoor and general industrial applications, brass provides mechanical strength and can support EMC requirements, while stainless steel is suited to corrosive, marine and hygienic settings.
A gland whose IP rating or clamping range falls short of the enclosure it serves silently downgrades the entire assembly to its own lower figure. Thread choice matters as much as material, since a mismatched or poorly sealed thread defeats the rating regardless of how the gland body is specified. The cable diameter must fall within the gland's clamping range, because a conductor outside that window breaks the seal the rating depends on.
IP Ratings vs NEMA Ratings
In the North American market, equipment is also commonly classified using NEMA enclosure types. NEMA explains that its enclosure ratings and IEC IP classifications should not be treated as directly interchangeable because NEMA evaluates additional environmental conditions, including factors such as corrosion and icing. NEMA's published comparison tables can indicate which IP classifications particular NEMA enclosure types meet or exceed, but the conversion does not necessarily work in the opposite direction.
The relationship runs one way with more confidence than the other, because NEMA also tests for conditions IP does not address, such as corrosion, icing, and construction integrity. No exact conversion between IP and NEMA exists, and treating a rough equivalence as an exact one is how specifications go wrong at the border between the two systems. For equipment crossing markets, verifying both ratings independently is the only safe approach.