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What Do Safety Boot Codes Like S3 and SRC Mean?

What Do Safety Boot Codes Like S3 and SRC Mean?

A string of letters on a boot label can look like an alphabet soup: S3, WR, HRO, SRC. Each one is actually telling you something specific about what that boot can and can't protect you from, and knowing how to read it means you're matching footwear to the job, not just trusting the box.

Two standards, two starting points

Safety and occupational footwear sit under two different standards, and the difference matters:

  • EN ISO 20345:2011 (Safety footwear) includes a protective toecap, tested to withstand 200J impact and 15,000N compression force.
  • EN ISO 20347:2012 (Occupational footwear) offers no toe protection at all, but must include at least one other protective feature to qualify.

The base classification

Every certified boot or shoe carries a base code that tells you which standard it meets:

  • SB (Safety Basic) confirms compliance with EN ISO 20345, meaning toe protection to the levels above.
  • OB (Occupational Basic) confirms compliance with EN ISO 20347, no toe protection, but at least one protective feature included.
  • SBH / OBH (Hybrid footwear) covers boots with a moulded rubber or polymeric lower and a leather or fabric upper. SBH includes toe protection, OBH doesn't.

Construction is also classified separately: Classification I covers leather or fabric uppers, Classification II covers moulded, all-rubber or polymeric construction, think wellington-style boots.

The S1 to S5 and O1 to O5 categories

Beyond the base SB or OB rating, footwear is usually classified further into S1 to S5 (with toe protection) or O1 to O5 (without). These build progressively, each category adding further protective requirements on top of the last, roughly:

  • S1/O1 covers the base requirements plus a closed seat region, antistatic properties, and energy absorption in the heel
  • S2/O2 adds water-resistant upper (WRU)
  • S3/O3 adds perforation resistance and a cleated outsole
  • S4/O4 and S5/O5 apply the same progression to all-rubber or polymeric boots, where the moulded construction already accounts for water resistance

Worth double-checking against the full EN ISO 20345/20347 standard if you're specifying for a particular hazard, since the exact requirements at each level are detailed and worth getting right.

The shortcut codes and what they actually test for

Code What It Means
E Energy absorption of the seat region, cushioning to reduce heel and ankle fatigue
FO Fuel oil resistance of the outsole, resists damage and swelling from hydrocarbons like petrol
P Perforation resistance, limited resistance to nails and sharp objects penetrating the sole
A Antistatic, dissipates static (resistance between 0.1 and 1000MΩ), limited resistance to mains voltage
C Conductive footwear, for explosive atmospheres, resistance of 0.1MΩ or less, no mains voltage resistance
WRU Water-resistant upper, limited resistance to water penetration through the upper panels
WR Water resistance across the whole boot (an 80-minute flex test in water); anything marketed as "waterproof" must carry this
SRA Slip resistance tested on ceramic tile with a soap solution, representative of most workplaces with water-based lubricants
SRB Slip resistance tested on steel with glycerol, representative of tougher indoor surfaces with oil-like lubricants
SRC Meets both SRA and SRB, suitable where surface and lubricant conditions can't be predicted
HRO Heat resistance of the outsole, withstands short-term contact up to 300°C for one minute without damage
HI Heat insulation, resists heat transfer up to 150°C for 30 minutes with less than 22°C internal rise
CI Cold insulation, resists cold transfer down to -17°C for 30 minutes with less than 10°C internal drop
AN Ankle protection, guards against transferred impact forces to the ankle
M Metatarsal protection, a guard over the top of the foot resisting up to 100J impact from falling objects (not available under EN ISO 20347)
CR Cut-resistant upper, boots only, protection extends a limited height up the leg
Electrical insulation Tested to EN 50321-1:2018, specifically for wellington boots used around live electrical installations

What's actually printed on the label

A compliant label typically includes: the size (UK and Paris points), the brand or trademark, the style name or model number, the date of manufacture (minimum month and year), a batch number for traceability, the standard number and date it's certified to, the protection category (e.g. S3 WR HRO SRC), the manufacturer or importer's name and address, and the relevant compliance marks.

Two marks matter for sales into different markets: the CE mark, confirming compliance with EU Regulation 2016/425 for sales into the EU and Northern Ireland, and the UKCA mark, confirming compliance under UK law (SI 2019/696) for sales in Great Britain. Dual marking means the product has been certified by both an EU-notified body and a UK-approved body.

Diagram of a BSIF safety footwear label showing UK8 EU42 sizing, brand logo, manufacture date 06/21, batch number P/O:1234, standard EN ISO 20345:2011, protection category S3 WR HRO SRC, style code ABCD, manufacturer address, and CE and UKCA compliance marks with a 5mm minimum height requirement, each element labelled with a callout line explaining what it represents.  Kept it descriptive rather than exhaustive since alt text this detailed can get long. If you want a shorter version for strict character limits, here's a trimmed option too:  Annotated safety footwear label showing size, brand, date of manufacture, batch number, EN ISO 20345 standard, protection category, and CE/UKCA marks with callouts explaining each field.

Why it matters for buyers

Reading these codes properly means you're matching footwear to the actual hazard, chemical splash calls for WRU or WR, electrical work calls for the specific EN 50321-1 rating, cut risk calls for CR, cold storage calls for CI, rather than relying on a product description or assuming "safety boot" covers everything.

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References

PERSONAL PROTECTIVE EQUIPMENT Safety and occupational footwear marking, BSiF