Chemical Protective Clothing Permeation Class (EN 14325) & Cumulative Permeation Estimate

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 6 inputs are read from the form on every keystroke: Normalised Breakthrough Time, Steady-State Permeation Rate, Report Uses the ASTM F739 Criterion, Planned Wear Time, Area in Contact with the Chemical and Acceptable Cumulative Dose.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves EN 14325 Permeation Class together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Minutes Short of the Next Class, EN Class Scale Applies, Wear Time Runs Past Breakthrough, Minutes Worn After Breakthrough, Estimated Mass Permeated over the Wear Time, Share of the Acceptable Dose, Minutes until the Acceptable Dose and Mass per Hour over the Contact Area — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

Substituting

Cut the task to 60 minutes and nothing is counted, because the wear ends before breakthrough; a Class 3 label is no help for a 120-minute task with this chemical.

How to use it

1. Work through the input groups in order — Permeation Test and Wear. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read EN 14325 Permeation Class in the dark results panel — that is the headline figure, expressed in class.
4. Check the supporting rows underneath (Minutes Short of the Next Class, EN Class Scale Applies, Wear Time Runs Past Breakthrough, Minutes Worn After Breakthrough, Estimated Mass Permeated over the Wear Time, Share of the Acceptable Dose, Minutes until the Acceptable Dose and Mass per Hour over the Contact Area) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing EN 14325 Permeation Class before a trial is booked, so machine time and material in Nonwovens & Technical Textiles are committed against a calculated figure rather than an estimate.
• Costing and quotation — EN 14325 Permeation Class is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Normalised Breakthrough Time) shows how much of the gap in EN 14325 Permeation Class each variable explains.
• Teaching and study — the accepted ranges bracket normal Nonwovens & Technical Textiles practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• Classes per EN 14325 clause 4.11 as printed in Lakeland's chemical permeation database: a class is met when the normalised breakthrough time is more than 10, 30, 60, 120, 240 or 480 minutes for classes 1 to 6; under 10 minutes a database lists "immediate". Normalised breakthrough is the moment the permeation rate reaches 1.0 µg/cm²/min, not the first molecule through: the chemical has been permeating at a rising rate before it, which is why the database carries the standard's warning that it can be dangerous to base safe wear time on the breakthrough time alone. ASTM F739 records breakthrough at 0.1 µg/cm²/min; EN ISO 6529 offers both rates, and the 1.0 figure is the one used for EN classes, so an ASTM time cannot be classed here. The cumulative estimate applies the steady-state rate to every minute after breakthrough and ignores permeation before it; the real curve climbs to the plateau rather than jumping, so the figure is a planning estimate, high in the first minutes after breakthrough and low if the rate is still rising. **Class, dose limit and wear time are the safety adviser's decision; this is a reading aid for the test report.**
• Every input is bounded to the range normal practice occupies (Normalised Breakthrough Time 0 to 2000 min, Steady-State Permeation Rate 0.1 to 10000 µg/cm²/min and Report Uses the ASTM F739 Criterion 0 to 1 1 = yes, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Standards and further reading

• EN 14325, Protective clothing against chemicals: test methods and performance classification of chemical protective clothing materials, seams, joins and assemblages (clause 4.11, permeation classes).
• EN ISO 6529, Protective clothing, protection against chemicals: determination of resistance of protective clothing materials to permeation by liquids and gases.
• ASTM F739, Standard Test Method for Permeation of Liquids and Gases through Protective Clothing Materials under Conditions of Continuous Contact: breakthrough at 0.1 µg/cm²/min.
• EN 14605, EN ISO 13982-1 and EN 13034: the Type 3 and 4, Type 5 and Type 6 suit standards that call up the EN 14325 classes.

Questions people ask