Standard explainer · EN 397
A hard hat is such a fixture of site life that almost nobody reads its label — which is a shame, because the label answers the questions people actually argue about: what it protects against, when it expires, and whether that mountaineering-style helmet is allowed.
What it tests
EN 397 is the industrial safety helmet standard. Its core tests are about one scenario: something falling on your head. The shell and harness must absorb a specified impact and resist a pointed striker penetrating to the skull, and the chinstrap must release under a controlled load — so a snagged helmet doesn't strangle its wearer.
Two things follow. First, EN 397 protection is overwhelmingly top-down — it's not designed for side impacts or falls (that's where the climbing-style standard enters, below). Second, the protection lives in the gap between shell and harness — which is why stuffing a beanie under the harness or storing gloves in the crown genuinely compromises it. Cold-weather liners designed for helmets exist for exactly this reason.
The marks
| Mark | Means | Who needs it |
|---|---|---|
| -20°C / -30°C (LT) | Tested at low temperature | Winter outdoor work, cold stores |
| +150°C | Very high temperature test | Hot process environments |
| 440V a.c. | Electrical insulation test | Work near LV electrical risk |
| MM | Molten metal splash | Foundries and casting |
| LD | Lateral deformation resistance | Crush-risk environments |
The neighbours
EN 812 bump caps protect against walking into things — pipework, vehicle sills, racking. They are not safety helmets and don't satisfy a hard-hat rule; their home is under-vehicle work and low-clearance maintenance.
EN 12492 climbing-style helmets — the vented, chinstrap-retained style spreading through scaffolding and work-at-height trades — prioritise staying on the head in a fall and tolerate side impacts better, but their chinstrap deliberately does not release like EN 397's. Many sites now accept or prefer them for work at height; some mandate EN 397. The site rules decide — check before standardising a crew on either.
Whichever style: helmets carry a moulding date stamped into the shell, and makers specify a service life from it (commonly 3–5 years, less under heavy UV). Scuffs are cosmetic; chalky, faded or cracked shells are retirement notices — and any helmet that's taken a real impact is done, visibly damaged or not.
Checks
Questions
From the moulding date stamped into the shell, makers typically specify 3–5 years of service — less under heavy UV exposure. Retire earlier for chalking, cracking or loss of flexibility, and immediately after any significant impact regardless of appearance.
No — bump caps (EN 812) protect against striking your head on fixed objects, not falling objects. They don't satisfy a site hard-hat requirement; their place is low-clearance work like vehicle bays and plant rooms.
Increasingly yes, especially for work at height, because they stay on in a fall — but they certify to EN 12492, not EN 397, and their chinstrap behaves differently by design. Individual sites set the rule, so confirm before buying for a crew.
Not a standard beanie — it changes how the harness sits and absorbs impact. Use a helmet-compatible thermal liner designed to work with the suspension; several makers produce them for winter site work.
Helmets, masks, eye protection, gloves and the rest of the PPE wall, certified and in stock.