EN ISO 374-1:2016+A1:2018 grades chemical-protective gloves as Type A, Type B or Type C based on how many of the 18 listed test chemicals reach a defined permeation performance level under EN 16523-1 [S2][S5].
Type A requires permeation performance level 2 or higher on at least six listed test chemicals, Type B the same level 2 on at least three, and Type C only level 1 on at least one chemical; the type letter is therefore a breadth indicator, not a guarantee that the glove suits your specific substance [S1][S2][S5][S8].
What the type letter actually measures
EN 16523-1 measures the normalised breakthrough time, defined as the point at which the permeation rate reaches 1.0 µg cm⁻² min⁻¹, and maps that time to a six-step permeation performance level: level 1 above 10 min, level 2 above 30 min, level 3 above 60 min, level 4 above 120 min, level 5 above 240 min, level 6 above 480 min [S2]. The Type A, B and C bands are then cut across those levels: A and B sit on the level-2 floor (>30 min), C drops to the level-1 floor (>10 min), and only A demands the six-chemical breadth [S2][S5][S8].
Three specimens are tested per chemical; if all three fall within 20% of their mean the test is validated and the lowest result is reported, otherwise a fresh set of three must be run, which is why a glove datasheet can quote different levels for different code letters under a single Type A marking [S2]. A reusable nitrile chemical-protection glove cited in the source material reports level 6 against sodium hydroxide 40% and n-heptane but only level 2 against methanol, all under one Type A [S2]. That gap is normal and is exactly why the safety gloves category is read chemical by chemical, not by type letter alone.
The 18 code letters and why concentration matters
The 2016 revision expanded the test list from 12 to 18 chemicals, adding code letters M to T: nitric acid 65% (M), acetic acid 99% (N), ammonium hydroxide 25% (O), hydrogen peroxide 30% (P), hydrofluoric acid 40% (S) and formaldehyde 37% (T), joining the original A methanol, B acetone, C acetonitrile, D dichloromethane, E carbon disulphide, F toluene, G diethylamine, H tetrahydrofuran, I ethyl acetate, J n-heptane, K sodium hydroxide 40% and L sulphuric acid 96% [S2][S5].
Each code letter is locked to a specific concentration, so a marking that lists K means sodium hydroxide at 40%, not a generic caustic solution, and a 30% sodium hydroxide exposure needs separate verification because the permeation behaviour of dilutions is not assumed identical [S2][S5]. Letters Q and R are intentionally absent from the published sequence and should never be back-filled with a workplace chemical by analogy [S5]. For procurement, the rule of thumb is: match the letter, the concentration, and the permeation level against the SDS of the substance actually in use.
Type A vs B vs C: a procurement decision matrix
Type A is the default choice for mixed-exposure workshops because the six-chemical breadth usually covers solvents, acids and bases a maintenance technician will meet in a week; Type B targets narrower solvent or cleaning tasks where three tested chemicals are known and sufficient; Type C is reserved for very short, low-risk contact such as a 10–15 min splash or wipe-down where level 1 (above 10 min breakthrough) is acceptable [S2][S5][S7].
On cost, Type A reusable nitrile and butyl gloves sit at the top of the range, Type B mid-weight nitrile or neoprene sits noticeably lower, and Type C is dominated by thin disposable nitrile around 0.12 mm thickness, which is also why the source material notes that "most chemical protective gloves can be assigned to type class A; only thin disposable protective gloves will be assigned to types B and C" [S1][S4]. On service life, Type A reusable gloves typically outlast Type C disposables by an order of magnitude when degradation is managed under EN ISO 374-4:2019, but only if the degradation rating for the actual chemical is checked, because a glove can hold its permeation rating yet swell, harden or crack in service [S2][S7].
Who Type A is for: laboratory and chemical-handling staff exposed to several substances, EHS teams standardising site-wide PPE, and procurement writing framework specifications where the chemical list is wide. Who it is not for: a single-substance, short-duration task where a thinner, cheaper Type C or Type B glove is the better ergonomic fit, and any application where the SDS chemical is not on the 18-letter list, in which case EN ISO 374-1 cannot certify the glove for that substance and a different evidence route is needed [S5][S7].
Degradation, penetration and the other parts of EN 374
The type letter does not cover mechanical penetration or chemical degradation. EN ISO 374-2:2019 is a penetration test against microorganisms and chemicals, and EN ISO 374-4:2019 measures degradation, defined as a change in properties such as brittleness, swelling or shrinkage after contact with the chemical, which is reported separately because a glove can pass permeation and still fail in service [S2][S1].
EN ISO 374-5:2016 covers bacteria, fungi and viruses, with an additional marking for viruses when ISO 16604 is passed, and it is the part that matters for clinical, laboratory and biological-risk environments; the chemical-part marking alone does not imply biological protection [S2][S1]. Buyers who need both chemical and biological protection should require both markings, not assume one implies the other.
Specification language that does not fall apart on audit
"EN 374 certified" on a purchase order is unverifiable and is the single most common tender error against this standard, because the standard is a family of five parts plus EN 16523-1, each with its own current edition, and the gloves also fall under EN ISO 21420:2020 for general requirements [S2]. A defensible specification names the part, the year, the type letter, the code letters, the permeation level per chemical, and the degradation result for the chemicals in scope; for example, "EN ISO 374-1:2016+A1:2018 Type A, codes A B C D E F, minimum level 2 each, EN ISO 374-4 degradation data for chemicals A, K and L provided" [S2][S5][S7].
For Great Britain specifically, a government proposal published on 16 September 2026 would add EN ISO 374-6:2025, protective gloves for hairdressers, to the designated standards list for PPE at 00:01 on 15 October 2026 unless the notice is withdrawn or amended, which is a sector-specific addition rather than a replacement of -1 [S5]. Internationally, ISO 374-1:2024 was published in July 2024 with ISO 374-1:2016 listed as withdrawn at ISO level, yet EN adoptions, designated standards, certificates and product documents do not all change on the same date, so the edition printed on the declaration of conformity is the controlling reference until a formal transition date is published [S5].
Selection rules that survive a COSHH review
Step 1: pull the SDS for every substance in the task, list the CAS numbers and concentrations, and map each to the 18 code letters; substances outside the list cannot be covered by EN ISO 374-1 and need a manufacturer permeation dataset instead [S5][S7]. Step 2: set the minimum permeation level per chemical from the contact time and temperature, with level 2 (>30 min) as the usual floor for incidental contact and level 3 to 4 for continuous immersion [S2][S7]. Step 3: check EN ISO 374-4 degradation for those chemicals, because the same glove can pass permeation and still fail mechanically within an hour of use [S1][S2]. Step 4: confirm EN ISO 374-5 if biological risk is in scope, and EN ISO 21420:2020 for general glove requirements such as pH, chrome and dexterity [S2].
For ergonomic and length decisions not covered by EN 374, mechanical risk is governed by EN 388 and thermal risk by EN 407, both of which sit on the same marking template, and a glove specified only for chemicals without mechanical and thermal entries will underperform in most real workshops [S3].
Trackable signal 1: the GB designated-standards notice expected around 15 October 2026 for EN ISO 374-6:2025, which signals how actively the UK is refreshing PPE designations in 2026 and is a useful calendar marker for any safety gloves framework tender closing in Q4. Trackable signal 2: the gap between ISO 374-1:2024 publication and a formal CEN/EN adoption date, which will determine when Type A/B/C markings on existing gloves have to be re-issued and is the trigger for re-checking every certificate of conformity currently on file [S5].
The underlying component specifications are covered under dry type transformer, and chemical anchor.
See also our earlier report, Compact vs Tie-Rod Pneumatic Cylinder: Footprint Decision Map.