Insulating Gloves Class 00–4: The Complete Reference Table

Every figure behind insulating glove selection in one place: the IEC 60903 Class 00–4 maximum use voltages and proof test levels, the colour convention, category letters, Type I versus Type II, and the storage and re-test rules once the gloves are in service.

Choosing an insulating glove looks like a single decision — what class? — but most specification errors happen on the two questions either side of it: what the class actually limits, and what the glove has to be re-tested against once it is in service. This page is the reference companion to the insulating mat thickness guide; the figures below come from IEC 60903 and its North American counterpart ASTM D120, and where the two differ we say so.

1. The class table

IEC 60903 and EN 60903 group insulating gloves into six classes. The class is the designation marked on the glove and its label, and it is the only figure that defines what the glove may be used on.

The two voltage columns are not interchangeable, and the wide gap between them is not a safety margin to be spent — see the next section.

2. Maximum use voltage is not the proof test voltage

This is the single most expensive mistake in glove procurement. A buyer asks for "a 20 kV glove" and receives a Class 2 — because 20 kV is the class's proof test voltage, while its maximum use voltage is 17,000 V AC. The glove is compliant and correctly labelled; it is simply one class lower than the installer assumed.

3. Colour is a North American convention

Where glove colour is used as a class indicator, it follows the ASTM D120 convention:

A dual-certified glove sold outside North America may be coloured differently, and colour is not a substitute for the marking. Classify from the class designation on the glove, never from its colour.

4. Category letters: what the glove resists

Gloves certified to IEC 60903 can carry additional category letters for resistance to specific agents. They are additive to the electrical classification, not a substitute for it.

A glove marked R/C is therefore resistant to acid, oil and ozone, and rated for extremely low temperatures. If the working environment involves any of these, the letters belong on the purchase order alongside the class.

5. Type I and Type II

Type matters outdoors and anywhere with ozone-generating equipment. A Type I glove used in those conditions degrades faster than its class suggests.

6. Thickness: what the standard does and does not fix

IEC 60903 sets a maximum thickness for each class in its own table, and ASTM D120 sets thickness requirements that are not the same. The two are not interchangeable: a thickness figure quoted from an EN glove cannot be applied to an ASTM-sourced one, and vice versa.

For that reason this reference deliberately does not print a thickness column. Take the figure from the datasheet of the glove actually being supplied. Charts circulating online that pair a thickness to a voltage class without naming the standard behind them should be disregarded.

7. In service: storage, issue and re-test

The rule that catches people out is the middle one: a Class 2 glove sitting in stores does not stay compliant indefinitely. Past twelve months from manufacture it must be re-tested before it can be issued, even though it has never been worn.

For Class 00 and Class 0 the position is different — the routine dielectric re-test is not a standard requirement, and the working check is the visual inspection plus the air-leak test before each use. That is a lower testing burden, not a lower duty of care.

8. Working without leather protectors

If a rubber glove is used without a leather protector over it, go one voltage class higher than would otherwise be required — Class 00 and Class 0 excepted.

Where protectors are worn, the glove cuff must extend past the protector cuff so there is enough flashover cover between the two:

9. Writing the purchase order line

A glove specification that survives inspection names the standard, the class, the category letters, the type and the length:

Change the class, category letters and length to suit the installation — but keep the structure. The class figure and the words "maximum use voltage" are the parts that prevent the misunderstanding in section 2.

The classes above cover gloves rated to 36 kV. For the corresponding rubber matting classes and the thickness question that comes with them, see the insulating mat thickness and voltage reference.

Gloves in the classes covered here are supplied as the Rubber Insulating Gloves 10 kV – 35 kV and the 35 kV Insulating Rubber Gloves for live-line work.

If you are specifying gloves and want the class confirmed against your network voltage, send us the maximum use voltage of the installation and the working conditions. We will confirm the class, the category letters and the available lengths, and return the type test report for the class quoted.