Shopify Chemical Glove EN 374 Breakthrough Time Schema — EN 374-1 Incidental Contact Splash Symbol vs EN 374-3 Sustained Immersion Permeation Breakthrough Time (Class 1 >10 Min to Class 6 >480 Min), Permeation Differs from Penetration, Chemical Code Letters A–P Are Specific Test Chemicals Not Universal Coverage

ANSI/ISEA 105:2016 (American National Standard for Hand Protection Classification) includes chemical resistance ratings for the US market that differ from EN 374. ANSI/ISEA 105 chemical resistance is rated by performance level for three chemical classes: Permeation (similar to EN 374-3): Level 0 (breakthrough within 10 minutes, EN Class 1 equivalent) through Level 6 (>480 minutes, EN Class 6 equivalent) — the minute thresholds match EN 374 classes. Degradation: Level 0 (severe degradation) through Level 4 (no significant degradation) — qualitative observation of physical changes in glove material. Penetration: Level 0 (fails test) through Level 3 (passes highest quality test). The key practical difference: ANSI/ISEA 105 uses the same 0–6 scale for permeation as EN 374-3 uses Classes 1–6, with equivalent minute thresholds. A product marked EN 374-3 Class 4 and a product marked ANSI/ISEA 105 Permeation Level 4 both claim breakthrough >120 minutes — but they were tested with different chemicals, different test protocols, and the thresholds may align differently at exact boundary conditions. ANSI 105 tests against a specific set of US-standard test chemicals rather than the A–P EN 374 list — they may overlap but are not identical. Encode glove.ansi105_permeation_level for US market products in addition to glove.en374_class for EU market products. Never substitute one for the other without confirming test chemical equivalence.

EN ISO 374-5:2016 covers protection against microorganisms — specifically bacteria and viruses. This is a separate standard from EN 374-3 chemical permeation. EN 374-5 markings: B marking (bacteria icon): the glove passed the EN 374-2 penetration test at AQL 1.5 or better — indicating sufficient physical integrity to resist bacterial penetration through pinholes. V marking (virus icon): the glove passed viral penetration resistance testing per ISO 16604:2004 (Phi-X174 bacteriophage as surrogate virus) — testing for penetration of viral-sized particles through glove material. The V marking is particularly relevant for healthcare workers, laboratory personnel handling biological samples, and workers in environments with potential blood or bodily fluid exposure. Chemical gloves with V marking do not necessarily have better chemical permeation resistance — the V mark addresses biological, not chemical, barrier performance. A latex surgical glove might carry a V mark (excellent viral barrier) but have poor chemical permeation resistance to organic solvents. Encode glove.en374_bio_class as 'B' (bacteria-rated), 'V' (virus-rated), or 'B+V' (both). Do not interpret the V mark as indicating chemical resistance — it only addresses biological barrier performance per EN 374-5.

Glove thickness affects breakthrough time significantly for the same material — a thicker glove provides a longer diffusion path for permeating chemicals. However, thickness increases breakthrough time in a non-linear relationship that depends on the chemical's diffusion coefficient in the material. For most chemical-glove material pairs, doubling the thickness roughly doubles the breakthrough time, but this relationship breaks down at extremes. Example for nitrile vs toluene: 4-mil nitrile: approximately 5 minutes breakthrough. 8-mil nitrile: approximately 15 minutes. 15-mil nitrile: approximately 25 minutes. 30-mil nitrile: approximately 55 minutes. A 30-mil nitrile glove provides only ~55 minutes breakthrough for toluene — still Class 2 or borderline Class 3. Butyl rubber at 15 mil provides >60 minutes (Class 3+) for toluene because butyl has a fundamentally lower diffusion coefficient for aromatic hydrocarbons. The important limitation: thickness can increase breakthrough time within the same material class, but cannot substitute for material selection when the fundamental chemical/material compatibility is poor. For a chemical where the material has high affinity (the chemical rapidly dissolves into the polymer), no practical thickness provides long breakthrough time. For such chemicals, a different material must be used. Encode glove.thickness_mil and glove.en374_class together — the class is valid only for the specific thickness tested. Do not extrapolate EN 374 class data to different thicknesses without confirming with manufacturer testing at the relevant thickness.

Many important industrial chemicals are not in the EN 374 A–P standard test list. For these chemicals, protection data must come from manufacturer-provided permeation testing rather than EN 374 standard markings. Common chemicals not in EN 374 A–P and typical glove performance: Hydrofluoric acid (HF) — not in EN 374 list. HF is highly hazardous and permeates through many materials faster than the acid concentration would suggest. Neoprene 15 mil: ~60–90 min. Butyl 15 mil: ~60+ min. Best option: Teflon/PTFE laminate or manufacturer-tested specific HF gloves. Gasoline / petroleum naphtha — not in EN 374 list. Similar to aliphatic hydrocarbons (J series). Nitrile 15 mil: ~30–60 min. Viton: >480 min. Xylene (aromatic) — not in EN 374 list (toluene, code F, is the aromatic representative). Similar performance to toluene by material. MEK (methyl ethyl ketone) — not in EN 374 list (acetone, code B, is the ketone representative). Similar to acetone — butyl provides >480 min; nitrile <30 min. Formaldehyde (35%) — not in EN 374 list. Butyl rubber: >120 min. Nitrile: ~30–60 min at 35% concentration. Encode glove.permeation_tested_chemicals as a manufacturer-specific field listing all chemicals for which the manufacturer has published breakthrough data, not just the 3 standard EN 374 code-letter chemicals. This field is the primary routing mechanism for non-standard chemicals.

Double-gloving — wearing two gloves simultaneously, often a thin inner glove under a thicker chemical-resistant outer glove — is used in specific scenarios. Breakthrough time extension: theoretically, two layers of the same material roughly double the total effective thickness and extend breakthrough time proportionally. However, the relationship is complex — if the outer glove is breached, the inner glove has already been exposed to chemical diffusing through the outer layer during the outer glove's permeation phase. The two-layer benefit applies to physical puncture protection (the inner glove provides a backup if the outer glove is cut) more than to molecular permeation protection. Healthcare and laboratory: double-gloving with two layers of nitrile or latex is standard in high-risk biological procedures to provide redundancy against physical failure (needle stick, sharps) and extend time before chemical permeation reaches the skin. Thermal comfort: a thin cotton liner inside a PVC or butyl outer glove improves comfort during extended wear without compromising outer glove chemical performance. Temperature extremes: inner thermal liner extends time before the outer chemical glove's material properties are affected by temperature change. Double-gloving limitation for chemical resistance: if the outer glove does not provide adequate breakthrough time for the chemical, the inner glove — typically the same or thinner material — will not add enough time to make the combination adequate. Glove material selection must be correct first; double-gloving provides physical redundancy, not a substitute for proper material selection. Encode glove.double_glove_compatible as 'yes' for gloves designed for use as the outer layer in a double-glove configuration (proper clearance for inner glove, no seam interference).