ESD-Antistatique

The difference between antistatic and ESD – a safety footwear example

This post is also available in: German French

There is often confusion between the terms ESD and antistatic, and not just when it comes to safety footwear. While one includes the other, to deduce the same is true in reverse is generally incorrect. Although both terms refer to contact resistance, there are fundamental differences between the two. Confused? Worry not. We are going to shed some light on the matter below. 

We previously explored the topic of electrostatic build-up and discharge in A new electrostatic test standard for safety gloves. This is something that many of you will already have experienced first-hand. Safety footwear generally represents the point of connection between the body and the floor. Electrostatic energy and contact resistance are therefore extremely important in this area. However, a distinction must be made between the antistatic properties of shoes and their electrostatic discharge (ESD) capability.

The applicable standard for safety footwear, EN ISO 20345, specifies a variety of requirements, including for electrostatic properties. It defines three areas, based on contact resistance: conductive, antistatic and electrically insulating footwear. For safety shoes to be labelled S1, they must fulfil the basic requirements plus the additional requirements for antistatic. The same applies to all subsequent safety classifications, for both industrial and occupational shoes. Shoes are antistatic if the measured contact resistance is in the range between 100 kiloohm (105 ohm) and 1 gigaohm (109 ohm). According to the standard, if contact resistance falls below this value, they are considered to be conductive, while a higher value means they are electrically insulating.

 

What are the reasons for this?

The EU standard stipulates that antistatic footwear should be worn to prevent electrostatic build-up and ensure it is discharged effectively. This is essential to eliminate the risk of electric shock from electrical equipment or live parts as well as that posed by sparks igniting flammable substances or vapours.

The aim is therefore to protect those wearing safety shoes (and their colleagues) from dangers related to electrostatic build-up.

 

So that’s antistatic explained. What does ESD stand for?

uvex Produktschutz AntistatikElectrostatic build-up and personal safety are not the only important considerations in industry, with controlled discharge also needed to protect components and equipment. Here, another standard comes into play that deals with electrostatic discharge (ESD): EN 61340-5-1 Protection of electronic devices from electrostatic phenomena. The ESD area defined in this standard represents a delimitation of the antistatic range indicated in safety footwear standard EN ISO 20345. The lower threshold of contact resistance is at 100 kiloohm and the upper threshold is at 35 megaohm (3.5 x 107 ohm). This therefore means that ESD-compliant shoes are always antistatic at the same time, but not all antistatic shoes are ESD compliant. For example, if contact resistance is measured as 100 megaohm, the shoes are antistatic but do not meet the ESD requirements. However, if the shoe contact resistance is just 1 megaohm, then the footwear is both antistatic and ESD capable.

uvex ESD-SiegelAs ESD relates to meeting the requirements for the product protection standard, the labelling must be separate from the CE marking. Consequently, safety footwear which complies with the standard features an additional yellow ESD symbol. If the shoes do not feature the special ESD symbol but are labelled S1, they are generally antistatic.  

 

Measurement methods and factors influencing results

Testing the antistatic properties of shoes for certification involves a test method under laboratory conditions. Before undergoing the test procedure, the shoe must first be conditioned over a defined length of time (in both dry and moisture-regulated atmospheres). The shoe is then filled with a total mass of 4 kg of stainless steel balls, which are connected to the contact resistance measurement device via a copper cable. The shoe is placed on a copper plate as the external electrode. The test voltage of 100 V DC is applied between the copper plate and the steel balls for one minute while recording the contact resistance of the footwear sample. This must exceed 100 kiloohm, but be less than or equal to 1 gigaohm.

Testing the ESD capability of shoes is slightly more difficult because there are a variety of different measurement procedures for the two standards. For EN 61340-5-1, the contact resistance value is measured for the person-shoe-ground system. This involves an employee standing on a conductive shoe testing electrode while wearing the safety footwear. The resistance is measured when they place their hand on a metal plate. If the measured contact resistance is less than 35 megaohm, the shoes are ESD capable.

The second standard, EN 61340-4-3, determines the contact resistance in a laboratory process. The test object is preconditioned at a predefined temperature and air humidity in a conditioning chamber. The standard distinguishes between three different climate classes as shown in the table below:

Climate class for pretreatment, conditioning and measurement Pretreatment Conditioning Measurement

1

96 (+10) h
(40 +/- 3) °C
RH < 15 %
96 (+10) h
(23 +/- 2) °C
(12 +/- 3) % RH
(23 +/- 2) °C (12 +/- 3) % RH

2

96 (+10) h (23 +/- 2) °C (25 +/- 3) % RH (23 +/- 2) °C (25 +/- 3) % RH

3

48 (+5) h (23 +/- 2) °C (50 + 5) % RH (23 +/- 2) °C (50 +/- 5) % RH

h = duration in hours, °C = temperature, % RH = relative humidity

 

Measurement is carried out once the test object has been conditioned. The shoe is placed on a stainless steel plate as the first electrode and a counter electrode is placed inside the shoe on the insole. Weight of 12.5 kg (+/- 2.5 kg) is then applied. A device measures the contact resistance between the two electrodes. It must be less than 100 megaohm for ESD certification to be granted for the respective climate class.

 

What factors can influence contact resistance for shoes?

It can sometimes be the case that footwear which has been labelled as ESD capable by the manufacturer then fails the control test carried out by the customer. However, this does not necessarily mean that the shoe is not ESD capable, as there may be a variety of reasons and influences that have affected the result. For example, the temperature of the shoe can impact the discharge capacity. Safety shoes which are left in the car overnight in winter would cool down so considerably that the contact resistance would be higher as a result. Similarly, the duration of wear can be an influencing factor, raising the moisture levels inside the shoes. Moisture generally raises discharge capacity. Other factors include alterations to the outsole or insole and whether contact areas are in any way dirty.

uvex 1 S1P SRC 8514

Various different uvex safety footwear models and variants have ESD certification for a wide range of applications. Your sales contact will be happy to provide support and guidance in choosing the perfect footwear model for your needs.

20 thoughts to “The difference between antistatic and ESD – a safety footwear example”

    1. Hey keerthana!

      Thank you for your nice comment. Is there anything in particular that you want to learn more about?

      With kind regards,
      uvex safety team

  1. hi,
    would like to check if the following models of safety shoes are available in singapore,

    8543 s1 src
    8540 s1 src
    8546 s1 src
    8512 s1 src

    and also if they are good for flat footed.

    thanks.

    1. Hello Mr. Leon and thank you for your interest in our safety shoes.

      We do not distribute safety shoes in Northeast and Southeast Asia right now or anytime soon.

      If you’ve got any further questions, please feel free to get back to us!
      With kind regards,
      uvex safety team

  2. Sehr geehrte Damen und Herren,
    Hervorragender Artikel. Besonders gefallen hat mir die Beschreibung der Testverfahren deren Messergebnis darüber entscheidet, ob ein Schuh ESD fähig ist oder nicht. Doch ESD Schuhe alleine reichen nicht aus. Von daher ist der ESD Schutz allgemein in Betrieben ein wichtiges Thema.

    Mit freundlichen Grüßen,
    Ronny

  3. Hello, I am interested in buying Halbschuh shoes 8514/1 schw / lime S1P PUR W10, I am in Lima – Peru, where can I buy them? Or do they ship to my country ?, or also in Cañifornia or Miami ?. Thank you.

    1. Hey Juan!

      Easy things first: S1-P-SRC-certified shoes also are penetration restitant to a certain extend.

      Regarding availability in your region: We do not distribute safety shoes in North or South America right now or anytime soon.

      Kind regards,
      uvex safety team

  4. Well this is a very interesting post! I never realized that there is a difference! Thank you for this detailed explanation. I will keep it in mind next time I am shopping for EMS boots.

  5. Can the dissipative properties of the shoe change over time? I have had some Uvex office S1 P SRA shoes for a few years (and loved them). These are SD rated (as opposed to ESD) and I believe these have a 100MΩ resistance limit by design (or are they 1,000MΩ – which standard do Uvex use?).

    Today, on the facility shoe tester, I passed conductivity on the right foot and failed on the left foot. The shoes are clean (as was the tester plate). It is a US calibrated system (so has a 100MΩ limit for pass/fail).

    Why would right/left feet differ?
    How would/could conductivity of the footwear change over time?

    1. Hey Stewart.

      Here’s what our product experts anwered: “I think that we speak about the uvex model 9542.2, this is the uvex office model with the marking S1 P SRA. This product is not an ESD model, it is only antistatic. Therefore the range of volume resistance is from 100 kiloohm to 1000 megaohm. If you need ESD footwear for your work, than you have to choose the model 9541.4 in S1 SRA or our new uvex business casual 9512.2 which is both ESD and S1 P SRC marked.

      A difference between the left and the right shoe is always in a certain range possible because of slightly variations during the production of the footwear. But because the tested footwear is not ESD certified, the limit of the test equipment is in this case too low for this model.

      A change in the volume resistance of footwear over the time is possible – because a lot of external influences like humidity, temperature, sweat, chemicals and the adherence of dust or dirt make the result higher or lower. This is the reason why in all recommendations for ESD areas there is the suggestion to check the volume resistance before entering the ESD area.”

      I hope this answers your questions – but feel free to get back to us if anything is till unclear!
      Kind regards,
      Jürgen from uvex safety team

  6. I just want to know if what kind of shoes should I be using? I work as a laundry person in a hotel, and most of the time I always got static in my hands and in my feet. I guess my shoes that I wore was not the proper shoes since I was surounded with heavy equipment and industrial machine.

    1. Hey Roxanne.

      That’s a difficult question as we don’t know much about your exact working conditions. When it comes to antistatics, not only your shoes have to have certain characteristics but also f. e. the floor. Don’t you have a person responsible for health and safety in your hotel that you can talk to about that?

      Regards,
      Jürgen from the uvex safety team

    1. Hey Vicky.

      Why don’t you send an e-mail with a few details about your company, your location and your specific needs to safety@uvex.de? I’m sure they’ll be happy to help you out.

      Kind regards,
      Jürgen from uvex safety team

  7. Hello uvex-safety.
    A difference between the left and the right shoe is always in a certain range possible because of slightly variations during the production of the footwear. But because the tested footwear is not ESD certified, the limit of the test equipment is in this case too low for this model.

  8. Dear, we use UVEX 1 S2 SRC shoes and are always struggling in the morning to pass our ESD tests.

    Is there a suggested time to wear the shoes before you perform the test.
    In other words: after how many minutes (in general) can we be sure that the moisture in the shoes is enough to pass the tests?

    Kind Regards!

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