The 'A' on a safety shoe stands for antistatic, and it describes something more precise than most people assume. It is not a coating, a feature or a bonus. It is a measured electrical property: the shoe must let charge drain from your body to the floor at a controlled speed, neither too fast nor too slow, and it has to prove that in a laboratory under two different humidity conditions.
It is also the most misunderstood marking in safety footwear, because the word "antistatic" sounds protective in a way the rating does not support. This guide covers the whole thing properly: where A sits in the code, what the test involves step by step, why the permitted window has a floor as well as a ceiling, what the rating explicitly does not do, and the everyday habits that quietly stop it working.
Where the 'A' Sits in the Safety Code
Antistatic is not an optional extra you hunt for. It is written into the base requirements of almost every safety footwear class, which is why so few product pages bother to mention it. If your shoe is S1 or higher, it is antistatic by definition.
| Class | Antistatic included | What else the class adds |
|---|---|---|
| SB | No, unless separately marked A | 200J toe cap and the basic requirements only |
| S1 | Yes | Closed heel region and energy absorption at the heel |
| S1P | Yes | S1 plus a perforation-resistant midsole |
| S2 | Yes | S1 plus water penetration and absorption resistance of the upper |
| S3 | Yes | S2 plus perforation resistance and a cleated outsole |
| S6 and S7 | Yes | The newer classes built around a waterproof construction |
SB is the one to watch. A pure SB shoe covers the toe cap and the basic requirements, and nothing more, so antistatic performance is not assumed. If you see SB alone on a label and you need antistatic, look for an explicit A alongside it. Our guide to safety shoe ratings from SB to S7 lays out how the whole ladder fits together.
What Static Actually Does to a Person at Work
Walking generates charge. Every step separates your sole from the floor surface, and that separation transfers electrons between the two materials. On an insulating floor in dry air, a person can accumulate a surprising amount of charge simply by crossing a room, and because the body is a conductor, that charge sits waiting for somewhere to go.
It goes somewhere in one of three ways, and each is a different kind of problem.
- The nuisance shock. You touch a door handle, a rack or a colleague and feel a sharp sting. Harmless in itself, but a flinch at the wrong moment near machinery, a ladder or a load is not harmless at all.
- The ignition risk. In an atmosphere containing flammable vapour, fine dust or powder, a spark from a discharging person can be enough to ignite it. The Health and Safety Executive is direct about this, advising that measures such as earth bonding and antistatic clothing and footwear help reduce the risk of static discharges in potentially explosive atmospheres.
- Component damage. Electronic components can be degraded by a discharge far below the threshold a person can feel. This is a real hazard, but it is governed by a separate and stricter specification.
Antistatic footwear addresses the first two directly and the third only partly. The shoe works as a deliberate leak path: rather than letting charge build and release in one sudden spark, it bleeds continuously away to the floor.
Inside the A Test, Step by Step
The test in ISO 20344 is more demanding than most people expect, mainly because of the conditioning. A shoe does not simply get measured once on a bench.
- Condition in dry air. The footwear spends seven days at 20°C and around 30 per cent relative humidity. This is the harsh case, because dry air is where static builds most readily and where materials tend to read as more insulating.
- Load the shoe. Four kilograms of steel balls go inside the shoe, sitting on a copper base plate, with a copper connection plate pressed down into the balls. The balls stand in for the foot, giving consistent, repeatable contact with the whole inner surface.
- Apply the voltage. 100 volts DC is applied for one minute and the resistance between the inside of the shoe and the plate beneath it is measured.
- Condition in damp air. The sample is then conditioned again, seven days at 20°C and around 85 per cent relative humidity, and measured a second time.
- Pass both, or fail. The resistance must land above 0.1 MΩ and at or below 1,000 MΩ in dry and damp conditions. A shoe that passes dry but drops out of range when humid does not earn the A.
Humidity changes how materials conduct. Many everyday materials become noticeably more conductive when damp and more insulating when dry. Requiring the shoe to stay inside one window across both extremes is what makes the A rating meaningful rather than a lucky reading on a good day.
Why Both Ends of the Window Matter
A single upper limit would be simpler. The standard sets a floor as well, and the reason is worth understanding because it explains why "more conductive" is not "better".
The three electrical bands of work footwear
Resistance measured between the inside of the shoe and the surface beneath it.
Conductive
Specialist use only
Antistatic
The everyday choice
Insulating
Fails the A requirement
So the floor at 0.1 MΩ exists to keep some resistance between your foot and the ground, and the ceiling at 1,000 MΩ exists to stop charge accumulating on you. Antistatic sits deliberately in the middle. It is not a weaker version of conductive footwear, it is a different answer to a two-sided problem.
Conductive, Antistatic and Insulating Are Three Different Ratings
These three get used loosely in conversation and they are not interchangeable. Electrically insulating footwear in particular is a separate product category with its own standard and its own withstand-voltage testing, and it is not something an S1P shoe quietly provides.
| Property | Conductive (C) | Antistatic (A) | Electrically insulating |
|---|---|---|---|
| Purpose | Drain charge as fast as possible | Drain charge at a controlled rate | Isolate the wearer from electrical potential |
| Resistance | 0.1 MΩ or below | Above 0.1 MΩ to 1,000 MΩ | Tested by withstand voltage, not this scale |
| Included in S1P | No | Yes | No |
| Typical use | Tightly controlled environments where any retained charge is unacceptable | General industry, warehousing, workshops, light trade | Specified electrical work under its own rules |
| Suitable for live working | No | No | Only within its own certified scope |
What the A Rating Does Not Do
This is the section that matters most, and the one most product pages skip. The A rating has hard limits, and the standard's own user information states them plainly.
- It is not electric shock protection. Antistatic footwear is not suitable for work on live electrical installations. It introduces resistance between the foot and the ground, and the accompanying user information is explicit that this cannot guarantee adequate protection against electric shock.
- It is not ESD certification. ESD footwear sits in a much narrower band under a different standard, and an A-rated shoe will not satisfy an ESD-protected area. We went through the gap in detail in ESD vs antistatic shoes, including why every ESD shoe is antistatic but the reverse is never true.
- It is not a complete answer to static on its own. The shoe is one part of a path that runs from your skin, through your sock, through the shoe, to the floor. Break any link and the path fails.
- It is not permanent. The standard's user information warns that the electrical resistance of antistatic footwear can be changed significantly by bending, contamination or moisture, and that the footwear might not perform its intended function when worn in wet conditions.
Class I footwear, made from leather and other materials rather than an all-rubber or all-polymeric construction, can absorb moisture over a long shift and become progressively more conductive. Where prolonged wet exposure is likely, the standard points towards Class II all-rubber or all-polymeric footwear instead.
Where Antistatic Footwear Is Genuinely Required
Because A comes bundled with S1 and above, most workers have it without ever asking for it. There is a smaller group for whom it is not incidental but specified, and for them the marking is a compliance item rather than a nice extra.
- Flammable and explosive atmospheres. Fuel handling, solvent work, paint spraying, and anywhere covered by dangerous substances regulations. Here the discharge is an ignition source, and footwear forms part of a wider static control approach alongside earth bonding and suitable clothing.
- Fine powder and dust environments. Flour milling, sugar, certain plastics and pharmaceutical powders can form an ignitable dust cloud, and static is a recognised ignition source in those settings.
- Electronics and precision assembly. Antistatic is the entry level here. Where components are genuinely sensitive, the site will specify ESD instead, which is stricter.
- Sites with a documented static control policy. Some warehouses, data centres and healthcare settings simply require it in writing, and that written requirement outranks every opinion, including ours.
The decision never belongs to the product page. Your employer's risk assessment and PPE policy determine what you need, and our guide to the UK PPE at Work Regulations covers where that duty actually sits and who carries it.
What Quietly Kills Antistatic Performance
A shoe that passed in a laboratory can stop performing in a workplace without anyone noticing, because nothing visible changes. These are the common causes.
- Replacement insoles. The charge path runs up through the footbed. A thick aftermarket insole from a sports shop can interrupt it entirely, and the shoe will look completely normal while doing so.
- Insulating socks. Heavy synthetic or thickly cushioned socks sit directly in the path between skin and shoe. Thin natural-fibre socks generally interfere less.
- Contamination on the outsole. Dried paint, adhesive, plaster, oil or a compacted layer of dust forms an insulating film across the contact surface.
- Moisture and prolonged damp. Water shifts readings in both directions, and the standard flags wet conditions specifically as a scenario where performance may not hold.
- Insulating floor coverings. A rubber mat, a thick epoxy coating or carpet breaks the final link to earth. Antistatic footwear on an insulating floor has nowhere to send the charge.
- Ordinary wear and flexing. Repeated bending changes the material over time, which is precisely why the standard recommends periodic retesting rather than trusting the original certificate indefinitely.
How to Check Yours Is Still Working
The standard does not treat the A rating as a one-off certificate. Its user information recommends that the employer establish an in-house test for electrical resistance, carried out at regular and frequent intervals.
In practice that ranges from a footwear tester at the entrance, common on electronics and static-controlled sites, to a periodic check with a suitable resistance meter as part of PPE inspection. If your workplace depends on antistatic footwear and nobody is measuring anything, the paperwork says compliant while the reality is unverified. For a broader view of what the class code promises and what it does not, what S1P certification actually covers is the companion piece to this one.
A Sensible Routine
- Keep the original insole in the shoe unless the manufacturer offers a replacement that maintains the rating.
- Clean the outsole when it picks up paint, adhesive or heavy dust, rather than letting it build.
- Treat a soaked pair as untrusted until dry, in any setting where static control genuinely matters.
- Retest after any significant contamination event, not just on a calendar schedule.
- Replace rather than nurse a pair with a worn, cracked or heavily contaminated outsole.
The Limits of the 'A' Rating
The A rating is a narrow, well-defined electrical property, and its value lies in how specific it is. It means a laboratory measured your footwear at 100 volts after a fortnight of conditioning across two humidity extremes, and found it sat inside a band chosen to balance two competing risks. That is a genuinely useful thing to know.
What it is not is protection from electric shock, a substitute for ESD certification, or a property that survives a thick aftermarket insole and a floor mat. Most workers already have it, because S1 and above include it as standard. The ones who depend on it are better served by understanding the whole path from skin to floor than by trusting the letter on the label and stopping there.
For the record on ours: the Xnexz PulseX and StrideX are certified EN ISO 20345 S1P, so antistatic performance is part of that certification, and they are designed to help disperse static build-up in suitable everyday work settings. They are not ESD-tested, and if your site runs an ESD-protected area you need a current ESD-certified product instead.
If S1P Is Accepted Where You Work
Try Xnexz in a real workday and tell us honestly how the fit, comfort and style hold up, and what we should improve. If your site specifies ESD, conductive footwear or a higher rating, buy what your safety officer specifies. That comes first.
Frequently Asked Questions
What does the A rating mean on safety shoes?
A means antistatic. The footwear has been measured and found to have an electrical resistance above 0.1 MΩ and no greater than 1,000 MΩ, so it drains static charge from the wearer to the floor at a controlled rate rather than letting it build up and discharge as a spark.
Are all S1P safety shoes antistatic?
Yes. Antistatic performance is part of the S1 base requirement, so it carries through S1P, S2, S3 and the newer S6 and S7 classes. SB is the exception, since a pure SB shoe covers only the toe cap and basic requirements unless it is separately marked A.
Does antistatic footwear protect against electric shock?
No. Antistatic footwear is not suitable for work on live electrical installations. It adds resistance between the foot and the ground, which is not the same as electrical insulation, and the user information supplied with it states that it cannot guarantee adequate protection against electric shock.
How is antistatic footwear tested?
The shoe is conditioned for seven days in dry air at around 30 per cent humidity, then loaded with 4 kg of steel balls on a copper plate, and 100 volts DC is applied for one minute while resistance is measured. It is then conditioned for another seven days in damp air at around 85 per cent humidity and measured again. It must sit within the permitted band in both conditions.
What is the difference between antistatic and conductive footwear?
Conductive footwear, marked C, measures 0.1 MΩ or below and drains charge as quickly as possible. Antistatic, marked A, sits above 0.1 MΩ and up to 1,000 MΩ and drains it at a controlled rate. The antistatic floor exists so that some resistance remains between the wearer and the ground.
Can I put my own insoles in antistatic shoes?
It is best avoided. The static path runs from your foot through the footbed and out through the sole, so a thick aftermarket insole can interrupt it without any visible sign. If you need a different insole, ask the manufacturer whether one is available that maintains the rating.
How long does the antistatic property last?
There is no fixed lifespan. The standard's user information notes that electrical resistance can change significantly with bending, contamination or moisture, and recommends that employers set up an in-house resistance test carried out at regular and frequent intervals rather than relying on the original certificate.
Do antistatic shoes work on any floor?
No. The footwear is only one part of the path to earth. A rubber mat, thick coating or carpet can break that path, leaving the charge with nowhere to go regardless of how good the footwear is. Where static control genuinely matters, the flooring is specified alongside the footwear.
