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EN 374 Breakthrough Time vs Safe Contact Time: How to Set a Glove Change Rule (2026 Guide)
Fujian Jixiang E-commerce Co., Ltd
EN 374 performance levels say when a chemical starts to permeate a glove; they do not say how long the glove can be worn. This guide explains degradation, permeation and the practical change rule, with a decision table by performance level.
EN 374 breakthrough time is the elapsed time until a test chemical is detected on the inside of the glove at a defined permeation rate - it is not a safe wearing time. A glove rated at level 6 (more than 480 minutes) is not a glove you can wear for eight hours in that chemical, and a glove rated at level 1 (more than 10 minutes) is not necessarily unusable. The difference between the two numbers is the change rule you write yourself.
Three Words That Are Not Interchangeable
Penetration is the movement of a chemical through seams, pinholes or defects - a physical leak. Degradation is a change in the physical properties of the glove material, such as hardening, swelling or softening, after contact. Permeation is molecular movement through intact material, and it is the mechanism EN 374 measures.
A glove can show no visible damage and still be permeated. That is why a glove that "looked fine" at the end of a shift can still have delivered a dose to the wearer, and why the change rule cannot be based on visual inspection alone.
What EN 374 Actually Reports
Under the EN 374 series, a glove is tested against a defined set of chemicals and each chemical is assigned a performance level from the measured breakthrough time. Enclosures classify gloves into Type A, B or C by how many chemicals they resist at level 2 or above, and EN 374-5 covers protection against micro-organisms and, where claimed, viruses.
| Performance Level | Measured Breakthrough Time | What It Tells You | What It Does Not Tell You |
|---|
| Level 6 | More than 480 minutes | Resistance is durable under continuous contact | That an 8-hour shift is acceptable without a change |
| Level 5 | More than 240 minutes | Resistance holds for a long task block | How the glove behaves at elevated temperature |
| Level 4 | More than 120 minutes | Resistance holds for a multi-step task | Whether a second chemical in the mix changes the result |
| Level 3 | More than 60 minutes | Resistance holds for a single task block | Performance under mechanical stress or flexing |
| Level 2 | More than 30 minutes | Minimum level counted for Type A, B, C claims | Suitability for repeated contact cycles |
| Level 1 | More than 10 minutes | Short splash and incidental contact only | Any continuous immersion or repeated wiping |
The benchmark is the standard permeation rate of 1.0 microgram per square centimetre per minute. Breakthrough is declared when three consecutive sampling intervals exceed that rate, which means the reported number is a detection threshold, not a safety margin. A level 2 result of 30 minutes means the chemical was detected at 30 minutes - it does not mean the wearer was protected for 30 minutes.
ASTM F739 Gives a Different Number for the Same Glove
North American practice uses ASTM F739, which reports normalized breakthrough time and steady-state permeation rate. A glove tested under both systems can produce different numbers for the same chemical, because sample thickness, temperature and the detection sensitivity all affect the result. Procurement documents that mix EN 374 levels with ASTM F739 times without stating the basis create disputes at the claim stage that neither party can resolve.
Two practical rules follow. First, always cite the standard and the test chemical concentration alongside any number. Second, never convert a level to minutes and treat the conversion as a wearing limit.
From Breakthrough Time to a Change Rule
A defensible change rule uses the breakthrough time as an upper bound and then applies three reductions: one for the safety factor between detection and harm, one for the real task duration including handling time, and one for mechanical stress and temperature in the actual work environment.
| Task Pattern | EN 374 Level of the Selected Glove | Suggested Change Rule | Rationale |
|---|
| Incidental splash, occasional handling | Level 1 (over 10 min) | Change after each contact episode, not after a clock interval | Contact is intermittent; the glove should not be carried between episodes |
| Single task block, up to 30 minutes | Level 2-3 | Change at the end of each task block | Rule matches the block, not the shift |
| Repeated handling, 60-240 minutes | Level 4-5 | Change at half the declared breakthrough time | Absorbs handling time, flexing and temperature effects |
| Continuous immersion or long exposure | Level 6 | Change at 50 to 60 percent of breakthrough time, with a documented maximum | Even level 6 is a detection threshold, not a durability guarantee |
| Two or more chemicals in one task | Any level | Set the rule on the shortest breakthrough time in the mix | Mixtures are not additive and are rarely tested as mixtures |
| Elevated temperature work area | Any level | Apply an additional reduction and re-test if possible | Permeation accelerates with temperature; the standard test is not at process temperature |
Where Glove Selection Usually Goes Wrong
- Single-chemical thinking: a degreaser with a surfactant, a solvent and water is a mixture, and the breakthrough time of the mixture is not the breakthrough time of the solvent alone.
- Thickness conflation: a thicker glove generally resists longer, but 8 mil versus 4 mil is not a linear doubling of safe time, and the thicker glove costs dexterity.
- Reuse of gloves across tasks: a glove that handled a solvent in the morning and water in the afternoon has already been permeated when the second task starts.
- Relying on feel: swelling and softening are degradation signs, but permeation can occur before either is noticeable.
Documentation the Buyer Should Hold
Ask for the permeation test report, not the pictogram. The report should name the test standard, the chemical and its concentration, the sample thickness, the breakthrough time and the normalized permeation rate. For a supplier that cannot produce the report, the claim on the box is a marketing statement, and the change rule has no technical foundation.
Then write the rule into the work instruction, in the same place as the chemical's safety data sheet, and review it whenever the chemical or the process temperature changes. A change rule that is not written down is not a control - it is a habit.
FAQ
Q: Does an EN 374 level 6 glove mean I can wear it all shift?
A: No. Level 6 means breakthrough was not detected within 480 minutes under the standard test conditions. It is a detection threshold, not a durability guarantee, and it does not account for temperature, flexing, mechanical stress or mixtures - so the change rule still has to be set by the user.
Q: What is the difference between permeation and penetration in glove testing?
A: Permeation is molecular movement of a chemical through intact glove material, which is what EN 374 measures. Penetration is a physical leak through pinholes, seams or defects. A glove can resist penetration and still permit permeation.
Q: How do I set a glove change interval from a breakthrough time?
A: Use the breakthrough time as an upper bound, then reduce it for the safety factor, the real task duration and the working temperature. A common practice is changing at half the declared breakthrough time for repeated handling tasks and at 50 to 60 percent for continuous exposure.
Q: Why do EN 374 and ASTM F739 give different numbers for the same glove?
A: They use different test methods, sample thicknesses and detection approaches, and the reported values are normalized differently. Always cite the standard, the chemical and its concentration with the number, and never convert a performance level into a wearing limit.
Q: Which chemical governs the change rule when a task uses a mixture?
A: The one with the shortest breakthrough time. Mixtures are not additive and are rarely tested as mixtures, so the conservative approach is to set the rule on the worst-performing component and to reduce the interval further if the mixture contains a surfactant that improves wetting.