Quick answer: Safety boot codes like S1, S1P, S2, S3 and S5 come from EN ISO 20345 (the standard Portwest's Australian footwear is tested against, alongside AS 2210.3): each class adds specific protection on top of the last — a steel toecap alone is S1, add a penetration-resistant midsole for S1P, add a water-resistant upper for S2, and add a cleated sole on top of that for S3. If your job involves sharp debris on the ground (nails, metal swarf, glass), you need S1P or higher — S1 and S2 only protect the top and sides of the foot, not the sole.

Most people assume "safety boot" means one fixed level of protection. It doesn't — Portwest's own range spans everything from a light steel-cap trainer to a fully waterproof rubber boot rated for chemical exposure, and the difference between them is spelled out in a short code on the label that almost nobody reads properly. Here's what each letter and number actually means, and which one your job needs.

The safety class ladder: SB to S5 explained

Each class under EN ISO 20345 builds on the one before it — it's a ladder, not a set of unrelated options:

SB (Safety Basic): the minimum — a steel or composite toecap protecting against a 200-joule impact, nothing else guaranteed. Rarely sold on its own; almost every real product adds at least S1's extra features.

S1: SB plus antistatic properties, energy-absorbing heel, and a closed (not open-back) heel design. Good for dry indoor or light outdoor work where the only real risk is something falling on the foot.

S1P: S1 plus a penetration-resistant midsole — a steel or composite plate under the foot that stops a nail or sharp object coming up through the sole. This is the point where a boot becomes suitable for most general trade and construction sites.

S2: S1 plus a water-resistant upper (keeps the boot itself from soaking through) — but S2 does not include the penetration-resistant midsole. It's a common trap: an S2 boot looks tougher than S1 but is still not rated against sharp objects underfoot.

S3: S2 plus the penetration-resistant midsole and a cleated outsole for grip. S3 is effectively the "full protection" leather/fabric boot class — water-resistant upper, steel toecap, puncture-resistant sole, and proper tread. This is the default recommendation whenever you're not sure which class to buy.

S4 and S5: all-rubber or all-polymer construction (gumboots/wellingtons) rather than leather — fully waterproof by design. S4 covers the same base protections as S1; S5 adds the penetration-resistant midsole, making it the wet-conditions equivalent of S3. See our full Safety Footwear range for all classes side by side.

What the extra letters after the class actually mean

Beyond the base class, Portwest labels often add extra letters for optional protections tested separately. The common ones actually worth knowing:

HRO — Heat Resistant Outsole: the sole can contact a 300°C surface for a minute without melting or cracking. Relevant for asphalt, welding, and foundry work.

FO — Fuel and Oil Resistant: the outsole resists degrading on contact with fuel or oil. Standard on most trade and warehouse boots.

CI — Cold Insulation: the boot keeps the internal temperature from dropping more than 10°C when the outside sits at -17°C for 30 minutes. Look for this specifically for cold-store or freezer work.

HI — Heat Insulation: the reverse test — internal temperature doesn't rise more than 22°C against a 150°C surface for 30 minutes. Relevant for hot surfaces like roofing or road work in summer.

SR / SRC — Slip Resistant: tested grip performance on wet or contaminated floors. Older stock may still show "SRC" (the legacy combined-surface rating from the previous edition of the standard); newer Portwest listings simplify this to "SR."

Not every work boot has a safety toecap — S-class vs O-class

This is the mistake we see most often: assuming any boot that looks like a work boot has a protective toecap. It might not. Footwear tested under EN ISO 20345 (the "S" classes above) always includes a protective toecap. Footwear tested under the related EN ISO 20347 standard — marked with an "O" class instead (O1 through O4) — has none. O-class boots still offer genuine slip resistance, water resistance, and comfort features, but zero impact or compression protection for the toes. They're a legitimate choice for roles with no falling-object risk (light agriculture, food handling, janitorial work), but the wrong choice if there's any chance of something heavy landing on a foot.

Which class does your job actually need?

General warehouse or light trade work: S1P is the practical minimum — the penetration-resistant midsole covers the most common real hazard (stepping on something sharp), and it's the class most Portwest general-purpose boots and trainers are built to.

Construction, mining, or any site with sharp debris and rough ground: S3 as the default — it's the only leather/fabric class that combines puncture resistance with a proper cleated sole for uneven, contaminated ground.

Cold storage or freezer work: look for the CI marking specifically, on an S3 or S5 base — the class alone doesn't guarantee cold protection.

Wet, agricultural, or food-processing environments: S5 gumboots for genuine safety-toe protection in constant wet conditions; O4 only if there's no falling-object risk at all.

Light indoor or office-adjacent roles with occasional site visits: S1 is usually sufficient — don't default everyone into S3 gear they don't need.

The same layered logic applies to hand protection — see our Cut-Resistant Glove Levels guide for the EN 388 A-F breakdown.

Frequently asked questions