ESD safety footwear is defined by a contact-resistance band of 0.1 to 100 megohms (MΩ), tested to BS EN IEC 61340-4-3:2018, which is a strict subset of the 0.1 to 1,000 MΩ antistatic range called out in EN ISO 20344:2011 clause 5.10 [S2][S5]. The narrower upper limit is the engineering reason a plant can park a 20 V-damaged microcircuit next to an EPA floor and still survive the next footstep.
The two standards do not compete: EN ISO 20345 covers personal-safety footwear (mechanical, slip, antistatic), while EN 61340-5-1 governs protection of electronic devices from electrostatic phenomena, and the ESD band sits inside the antistatic window as a tighter, charge-dissipation specification [S1][S2]. For procurement, that means an ESD-marked boot is automatically antistatic, but the reverse is not true, and the wrong marking in an EPA is the kind of audit finding that pulls a production line.
Resistance Bands by Standard: Three Numbers to Memorise
EN ISO 20344:2011 sets the antistatic range at 0.1 MΩ to 1,000 MΩ measured at the contact electrode, with anything below 0.1 MΩ reclassified as conductive and anything above 1,000 MΩ treated as electrically insulating under EN ISO 20345 [S1][S5]. Rock Fall's 2018 guidance and V12 Footwear's standard summary both quote the same 0.1 to 1,000 MΩ window, which is the figure to write into a purchase specification when the site has flammables or explosive atmospheres but no EPA electronics [S2][S5].
BS EN IEC 61340-4-3:2018, the footwear test method referenced by EN 61340-5-1, tightens the upper limit to 100 MΩ for the ESD-dissipative classification, with a 0.1 MΩ floor, which gives a 10x smaller dissipation window and is the reason ESD boots discharge faster and more predictably [S2][S3]. For ANSI/ESD STM97.1 the equivalent system-level test requires the combined resistance of person plus footwear plus floor to stay below 1.0 × 10⁹ Ω (1 GΩ), which is the EPA "resistance-to-ground" ceiling applied at the body, not the shoe [S4][S6].
EPA vs Antistatic Zones: Where Each Rating Is Mandatory
Inside an Electrostatic Discharge Protected Area (EPA), where microcircuits can be damaged by discharges as low as 20 V, the controlling pair is EN 61340-5-1 plus ANSI/ESD STM97.1, and the footwear must hit the 0.1 to 100 MΩ band so charge bleeds off before it reaches a device pin [S3][S4]. Outside EPAs, in zones with flammable vapours, powders, or solvents, EN ISO 20345 antistatic is sufficient and gives a wider 0.1 to 1,000 MΩ tolerance, which is easier to maintain in dirty, oily, or wet conditions where 100 MΩ leakage paths are hard to keep clean [S1][S7].
For work on live or potentially live electrical parts, neither rating applies: dielectric or insulated footwear is the correct PPE, and the 18 kV dielectric strength of class-2 insulated boots, not contact resistance, is the relevant spec, with EH (Electrical Hazard) ASTM-rated boots limited to 600 V AC incidental exposure and explicitly not certified for live work [S2]. Mixing these up on a single site is the most common audit error, because EH, antistatic, and ESD sit on the same boot shelf but solve three different problems.
Comparison: Antistatic vs ESD Footwear on Four Decision Criteria
Set up as a side-by-side, the two ratings diverge on the criteria that drive specification choices. Resistance band: antistatic 0.1 to 1,000 MΩ, ESD 0.1 to 100 MΩ. Governing standard: EN ISO 20344:2011 / 20345 for antistatic, BS EN IEC 61340-4-3:2018 inside EN 61340-5-1 for ESD. Typical use: flammable atmospheres, solvent handling, general manufacturing for antistatic; PCB assembly, semiconductor backend, data-centre hardware rooms for ESD. Cost and availability: antistatic is commodity and broadly stocked, ESD-marked boots carry a 10 to 30 percent premium and a smaller model range [S1][S2][S3][S7].
The practical takeaway is that ESD is the more stringent version of antistatic: a tighter upper resistance limit means faster, more controlled charge decay, which is exactly what an EPA needs and what an explosive-atmosphere zone can live without [S2][S5]. For multi-zone facilities, the standard pattern is to write the EPA rooms to ESD and the bulk of the plant to antistatic, with floor-resistance and body-voltage tests done at the system level under ANSI/ESD STM97.1, not at the individual shoe.
Verification, Marking, and What to Check on the Box
Compliance is shown by the standardised ESD pictogram (a reaching hand inside a triangle with a strike-through, per EN 61340-5-1) and a printed resistance rating on the tongue label, with most safety footwear lines from uvex, Bekina, Rock Fall, and V12 carrying both the EN ISO 20345 safety class (S1, S2, S3, S4, S5) and the electrostatic property code [S1][S3][S5]. Without the pictogram, the word "antistatic" on a hangtag is marketing, not certification, and the 0.1 to 100 MΩ claim cannot be enforced.
For incoming inspection, the field test is a surface-resistance or wrist-strap comb tester set to 1 × 10⁹ Ω pass / 1 × 10⁷ Ω fail, applied to the person-footwear-floor loop per ANSI/ESD STM97.1, with retest on a six-month cycle or after any sole repair [S6]. Related measurement discipline for the floor side is covered in the insulation resistance tester and decade resistance box reference pages, which give the metrology behind those 1 GΩ pass thresholds. For complementary EPA dress code, the spec-side comparison of single-use versus reusable ESD garments sits in the anti-static disposables vs reusable ESD smocks decision guide, and floor-zone traction under oil is covered in the ribbed-top anti-slip safety mat spec guide.
Failure Modes and Common Spec Mistakes
The dominant field failure is contamination: oil, line-side grease, and anti-slip matting residue push the system resistance above 100 MΩ on an ESD boot, and above 1,000 MΩ on a nominal antistatic boot, so the EPA is suddenly not grounded [S4]. A second failure is sole material pairing: leather soles are naturally low-charge but humidity-dependent, PVC soles are high-charge, and an ESD boot dropped onto a non-ESD floor (or vice versa) breaks the EPA loop regardless of how good the boot is [S4].
Spec-side, the most common mistake is writing "ESD" on a purchase order for an antistatic-atmosphere job, which locks the supplier into the 100 MΩ upper limit and increases reject rates from dirty-sole returns. The fix is to spec by zone, not by worker, and to require the system test under ANSI/ESD STM97.1 rather than a single-footwear test result. For perimeter grounding hardware like wrist straps, workstation mats, and bench ground points, the engineering fundamentals are the same as those used in any anti-static equipment specification, where the 1 × 10⁶ to 1 × 10⁹ Ω window is the universal EPA operating range.
Limits of Antistatic, Limits of ESD
Antistatic footwear is not a substitute for EH-rated or dielectric insulated footwear where live electrical work is the hazard, and the 600 V AC ceiling on ASTM EH boots is incidental-exposure only, not a live-work permit [S2]. ESD boots will not protect a worker from a flammable-vapour ignition source any better than antistatic boots do, because the relevant ignition energy is set by spark energy, not by the 100 MΩ vs 1,000 MΩ difference at the sole [S1][S3].
For data-centre hardware rooms, paint lines, and powder-coating booths, the binding spec is the EPA-system test under ANSI/ESD STM97.1, with a 1.0 × 10⁹ Ω person-footwear-floor ceiling that the boots alone cannot meet, the floor has to carry its share of the conduction path. The take-away for buyers: pick the rating by zone, prove it with a system test, and never let "ESD" on a hangtag substitute for EN 61340-5-1 documentation plus a written EPA compliance plan.
Trackable signals to watch over the next procurement cycle: any revision to EN ISO 20345 or EN 61340-5-1 resistance band numbers, the next ANSI/ESD STM97.1 revision, and the uptake of combined S5 + ESD safety boots (Bekina's StepliteS FlexGrip and CleanGrip are early examples) for food, pharma, and cleanroom sites that need both waterproof and EPA-grade footwear in a single SKU [S3].