EN 343 rates rainwear with two numbers, 1–4 each: the first is water-penetration resistance (how hard the rain can hit before it gets through), the second is breathability (how fast sweat vapour escapes). A 5000mm hydrostatic head with Class 4 water penetration and Class 2 breathability reads as "4,2" — heavy rain protection with moderate breathability. Match the first number to your rainfall, the second to how hard the crew works.
Every rainwear spec sheet carries the same cryptic pair: "EN 343 4,2" or "3,1". Most buyers check the first number (the rain rating) and ignore the second (breathability) — then wonder why the crew is soaked with sweat by 10am. Here is what the two numbers actually mean, and how to match them to the work.
The First Number: Water-Penetration Resistance
The first digit (1–4) measures how much water pressure the fabric withstands before leaking — the hydrostatic head, in millimetres. Translated to weather:
- Class 1–2: light rain, short exposure — the "keep in the van" jacket
- Class 3: moderate to heavy rain for extended periods — the all-day outdoor crew
- Class 4: sustained heavy rain and driving wind — marine, utilities, winter roadwork
A 5000mm rating like our [RS-005 fleece-lined jacket](/products/rs005-fleece-rain-jacket/) sits comfortably in Class 3–4 territory: heavy rain for hours, not minutes. But the fabric rating is only half the story — seams must be taped or welded, zips covered by storm flaps, cuffs and hem sealed. A Class 4 fabric with an untaped seam is a Class 1 garment.
The Second Number: Breathability
The second digit (1–4) measures water-vapour resistance — how fast sweat escapes. This is the number that decides whether the crew wears the jacket or leaves it in the van:
- Class 1: vapour stays trapped — clammy within an hour of physical work
- Class 2: moderate escape — acceptable for light work, marginal for active crews
- Class 3–4: fast escape — the jacket breathes as hard as the wearer sweats
For active outdoor work, Class 3 breathability is the floor, not the ceiling. A jacket that blocks rain but traps sweat leaves the wearer wet from the inside — cold, clammy and looking for an excuse to take it off. At that point the rain rating is irrelevant.
Matching the Class to the Work
The right class is not the highest class — it is the class that matches the rainfall and the exertion:
| Crew | Rain exposure | Exertion | Recommended |
| --- | --- | --- | --- |
| Occasional outdoor (delivery, inspection) | Light, intermittent | Low | 3,1 or 3,2 |
| All-day outdoor (construction, landscaping) | Moderate to heavy | Moderate | 3,3 |
Buying 4,4 for a mild climate is a waste: the jacket is heavier, stiffer and more expensive than the work demands, and the crew leaves it behind. Buying 3,1 for a winter roadwork crew is worse: the jacket fails in the first storm.
The Hi-Vis Part Is Separate
EN 343 certifies rain protection only. A hi-vis rain jacket also needs EN ISO 20471 for its fluorescent colour and reflective tape — the two standards test different properties, and both must appear on the garment's documentation. A jacket certified only to EN 343 is rainwear; it is not compliant hi-vis rainwear. The full rainwear spec checklist is in our [buyer's guide](/blog/hi-vis-rainwear-buyers-guide/).
What to Specify
Tell us three things and we will match the class:
1. The worst weather the crew works through (not the average) 2. How physically hard they work in it 3. The market (EN 343 for Europe, or the local equivalent)
We will come back with the fabric, the class, and the honest breathability rating — not just the rain number.
[Send your climate and crew type](/#contact) — we will propose the EN 343 class and quote the garment within 24 hours.
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Fujian Rising Outdoor Products Co., Ltd. is a BSCI, SMETA and SCAN-audited manufacturer of outdoor workwear and PPE, serving brands in the EU, US, Canada and Australia since 2012.
Frequently Asked Questions
What does a 5000mm waterproof rating mean in practice?+
5000mm hydrostatic head means the fabric withstands a 5-metre column of water before leaking — roughly moderate to heavy rain for several hours. For occasional showers 3000mm suffices; for all-day outdoor work in sustained rain, 5000–10000mm is the practical range. The rating measures the fabric only — seams, zips and closures must also be sealed.
Is Class 4,4 always the best choice?+
Not necessarily — it is the most protective but also the most expensive and often the heaviest. A landscaping crew in a mild climate is better served by a lighter Class 3,2 or 3,3 garment they will actually wear than a Class 4,4 shell they leave in the van. Buy for the worst weather your crew works through, not the worst weather imaginable.
Why does breathability matter as much as waterproofing?+
Because sweat is water too. A jacket that blocks rain but traps body moisture leaves the wearer wet from the inside — clammy, cold and uncomfortable within an hour of physical work. The second EN 343 number (water-vapour resistance) measures how fast that moisture escapes. For active crews, Class 3+ breathability matters as much as the rain rating.
Does EN 343 certification include the hi-vis part?+
No — EN 343 certifies rain protection only. A hi-vis rain jacket also needs EN ISO 20471 for its fluorescent colour and reflective tape. The two certifications test different properties and both must appear on the garment’s documentation. A jacket certified only to EN 343 is rainwear, not compliant hi-vis rainwear.
About Fujian Rising Outdoor Products
BSCI, SMETA and SCAN-audited manufacturer of outdoor workwear & PPE since 2012. 865 workers, 250 computerized sewing machines. Serving brands in the EU, US, Canada and Australia.
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