Understanding EN ISO 374 – the chemical and micro-organism glove standard
EN ISO 374 is five separate standards, not one, and "EN 374 certified" on its own is unverifiable. What each part covers, how to read Type A/B/C and the code letters, and what to write into a specification.
EN ISO 374 is the standard a glove has to satisfy before it can claim protection against chemicals or micro-organisms. It is not one document but a family of five, and the single most common mistake in tender specifications is treating "EN 374 certified" as if it meant something on its own. It does not. Without a type, a code list and a part reference, the claim is unverifiable.
This article covers what each part does, how to read the marking on a box, and what to write into a specification. For medical gloves the relevant standard is EN 455 instead; many of our gloves are certified to both.
The five parts, and their current editions
Each part carries its own edition date. Citing "EN 374:2016" for the whole family is wrong, because the parts were not revised together.
Two changes catch out older specifications. Part 3 no longer exists as EN 374-3 – the permeation method moved out into EN 16523-1. And parts 2 and 4 were revised in 2019: both are first editions of the ISO text adopted by CEN without modification, superseding EN 374-2:2014 and EN 374-4:2013, with national adoption due by April 2020. General glove requirements moved too: EN 420:2003+A1:2009 was superseded by EN ISO 21420:2020, with national adoption due by September 2020.
What the 2016 revision changed
The 2016 revision of part 1 was substantial, and understanding it explains most of what appears on a modern glove box.
Type A, B and C
The classification is built on permeation performance levels, and this is the layer most summaries skip. Breakthrough is measured to EN 16523-1 as the normalized breakthrough time – the point at which the permeation rate reaches the normalized permeation rate, a fixed figure of 1.0 μg cm⁻² min⁻¹. The resulting time maps to a level:
The glove types are then defined against those levels, not against raw minutes:
This is why datasheets quote a level per chemical rather than a single type. Our own reusable nitrile chemical protection glove reports level 6 against sodium hydroxide 40 % and n-heptane and level 2 against methanol – all under one Type A marking. The type tells you the floor; the levels tell you the glove.
Two procedural points from the source worth knowing:
The 18 test chemicals
Each carries a code letter, and the standard also assigns a chemical class:
Note the concentration on S: hydrofluoric acid 40 %. Our own earlier version of this article said 60 %, as do a number of published summaries. The standard specifies 40 %.
Other chemicals outside this list may be tested where the application warrants it, and the results must be reported – which is the point of the next section.
So a glove marked "EN ISO 374-1/Type B, ABC" achieved at least level 2 against methanol, acetone and acetonitrile.
One requirement added by Amendment 1:2018 is easy to miss and worth using. Clause 6.3 now requires that the tested chemicals be given in the user instructions along with their performance levels, and that where chemicals outside the standard list have been tested, those performance levels be provided too. The base standard already required that all permeation results should be reported in the user instructions, and that degradation be determined for each chemical claimed in the marking. So the pictogram is a summary, not the record. Ask for the user instructions: they carry the actual performance levels, including for chemicals that never appear on a box.
Penetration, permeation, degradation – three different failures
The three mechanisms are often confused, and they fail in different ways.
Penetration (part 2) is bulk flow through a physical defect: a pinhole, a crack, a tear. Two test principles are defined. In the air leak test the glove is pressurised with air and a leak shows as a stream of bubbles; in the water leak test the glove is filled with water and a leak shows as droplets on the outside, examined immediately and again after 2 minutes (± 10 s). The standard notes the air leak procedure is not suitable for all gloves – parts of some gloves over-inflate while others inflate only partially – and where it proves unsuitable, only the water penetration test is carried out. For both methods, leaks within 40 mm of the edge of the liquid-proof area are disregarded, because that is the clamped zone.
Part 2 also carries an informative annex for production quality assurance, and it is the most directly useful table in the series for a buyer:
Sampling follows ISO 2859. The annex explicitly allows the purchaser and seller to agree a more stringent level than the table – which means an institutional buyer can specify Level 3 and be within the standard's own framework.
A glove that fails penetration testing offers no chemical protection at all, whatever its permeation figures say.
Permeation (EN 16523-1) is molecular passage through intact material. Nothing is visible. A glove can look perfect and still be transmitting solvent to the skin, which is why breakthrough time is the number that governs how long a glove may be worn in contact with a chemical.
Degradation (part 4) is where most published summaries – including our own earlier version of this article – get the method wrong. It is commonly described as an observation of swelling, cracking or discolouration. It is not. The normative method in EN ISO 374-4:2019 is a puncture resistance test: three gloves are conditioned at (23 ± 2) °C and (50 ± 5) % RH for at least 24 hours, six 20 mm specimens are cut from each – three exposed to the challenge chemical, three unexposed – and degradation is expressed as the percentage change in puncture resistance after exposure. An informative annex offers a weight-change test as an alternative, expressed as percent weight change with standard deviation.
Visual changes are still relevant, but as reported observations accompanying the measurement, not as the measurement: swelling, shrinking, brittleness, hardening, softening, flaking, disintegration, colour change or bleeding, and delamination must be noted in the test report.
The practical consequence is the same either way: degradation is not the same as failure. A glove may discolour without losing barrier performance, and it may retain its appearance while permeating badly. Read the degradation percentage alongside breakthrough time, never instead of it.
Biological protection under part 5
Part 5 handles micro-organisms, which were previously bundled into part 2. It defines two levels, and the pictogram distinguishes them:
The virus claim requires the extra test. A shield without the word does not cover viral penetration, and this distinction is worth checking on any glove bought for outbreak response. Gloves longer than 400 mm, or where the cuff is part of the claim, require additional cuff testing.
Part 5 also obliges the manufacturer to print a specific caveat in the user instructions: that penetration resistance was assessed under laboratory conditions and does not reflect actual performance in the workplace. That sentence is in the standard, not marketing hedging, and it is a fair summary of what all of this data can and cannot tell you.
What to require in a tender
A specification that says "EN 374 compliant" tells you nothing. Five lines fix it:
Then read the results against your own conditions. Published breakthrough times are measured at 23 °C on a flat material sample. Skin runs near 37 °C, gloves stretch over knuckles, and concentration and mechanical stress both shorten breakthrough. A laboratory figure is a comparative benchmark, not a promise about your workplace.
Key takeaways
Frequently asked questions
What is the difference between Type B and Type C? Type B requires at least permeation performance level 2 – breakthrough above 30 minutes – against a minimum of three test chemicals. Type C requires only level 1, above 10 minutes, against one. Type C is a low bar and should not be specified where sustained contact is expected.
Does EN ISO 374 certification mean a glove is suitable for my chemical? Only if your chemical is one of the 18 in the test list and appears in the glove's code letters, with a breakthrough time long enough for your task. Otherwise the certification says nothing about your application.
Is EN ISO 374 the right standard for medical examination gloves? Not on its own. Medical gloves are governed by EN 455. Many are certified to both, because a clinical glove often also handles disinfectants and cytostatics.
What does the four-digit code on some gloves mean? That is EN 388, the mechanical hazard standard – abrasion, cut, tear and puncture – not EN ISO 374. The two are frequently confused because both use a pictogram with codes beneath it.
Seventeen years sourcing and supplying medical gloves and PPE to governments, UN agencies, NGOs and healthcare systems. Writes on glove standards, quality management and responsible sourcing for institutional buyers, working from the source standards rather than secondary summaries.
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