Insulating gloves (class 00-4) per IEC 60903 — voltage classes and periodic retesting

The guide on insulating rods and switch sticks — periodic testing per IEC 60855 covers another piece of insulating tooling with similar periodic- testing logic. This article covers the most personal insulating protective equipment of all: the electrically insulating glove, standardised in IEC 60903.

The six voltage classes

IEC 60903 classifies insulating gloves by the maximum use voltage of the installation on which they may be used:

Class	Maximum use voltage (AC)
00	500 V
0	1,000 V
1	7,500 V
2	17,000 V
3	26,500 V
4	36,000 V

The higher the class, the thicker and stiffer the rubber typically is — a class 4 glove offers considerably less tactile feel and dexterity than a class 00 glove, which in practice is a trade-off between the required voltage level and the workability of the task.

Note: this classification is based on the use voltage of the installation, not the proof-test voltage the glove is subjected to at manufacture — the manufacturing test voltage for each class lies considerably above the stated maximum use voltage, as a safety margin.

Why periodic retesting is needed

Rubber ages: exposure to light, ozone, oils, greases and mechanical wear can gradually reduce a glove's insulating capability, without this always being visible to the naked eye. IEC 60903 (and the national/company procedures based on it) therefore requires a periodic electrical retest — in practice typically every 6 months — where the glove is re-tested at the proof voltage appropriate to its class. A glove that has not been retested within the prescribed period may no longer be used for live work until the test has been carried out.

The air test before every use

In addition to the periodic electrical retest, practice requires an air test immediately before every use: the glove is rolled or inflated to trap air inside, after which the user checks for a hissing sound or a visible, localised bulge indicating a pinhole or tear. This simple, quick-to-perform check is essential because a microscopic defect — for example from a sharp object, chemical attack or a manufacturing flaw — can go unnoticed in a superficial visual inspection, yet completely defeat the glove's insulating function at that exact spot.

Note: the air test complements, but does not replace, the periodic electrical retest. The air test detects physical pinholes and tears; the electrical retest also detects a reduced dielectric property of the rubber itself that does not necessarily come with a physical hole.

Leather protectors

For most classes, an insulating glove is worn together with a leather protector glove, which mechanically protects the vulnerable rubber insulating glove against cutting, abrasion and puncture during the work. Without this mechanical protection, an insulating glove that is otherwise electrically sound can still be damaged during use.

Practical relevance

When assessing PPE for live working (see also the guide on live working and the guide on PPE in general), it is important to check that the insulating glove worn has the correct class for the relevant installation voltage, that the periodic retest date (typically marked on the glove itself or its packaging) has not expired, and that the user actually performs the air test before every use rather than only assessing the glove visually.

Common mistakes

Using a glove of too low a class for the actual installation voltage, on the assumption that "an insulating glove" suffices for any voltage.
Letting the periodic electrical retest interval lapse and continuing to use the glove without checking the retest date.
Performing only a visual inspection and skipping the air test — a microscopic pinhole is often not visible to the naked eye but is detectable with an air test.
Using an insulating glove without a leather protector for work with an increased risk of mechanical damage (sharp edges, rough surfaces), which can damage the rubber glove during the work itself.