Safe foot forward
25 November 2021
For many years there has been a lot of confusion surrounding the electrical properties of footwear which are identified by the various markings found on footwear. Lloyd Preston gives an overview of the properties offered and their suitability to certain end uses.
In the new draft EN ISO 20345/6/7:2021, a new term is used for these products formally known as “conductive”. This will be changed to “partially conductive” in name only. This is done in order to prevent confusion between this and a proposed new product type in a standard for live electrical working that intends also to use the term conductive. The testing, marking and properties are unchanged.
This type of footwear has a resistance of 1 x 105Ω (100kΩ) or less in a dry atmosphere. The product can be identified by the marking of the category of protection “C”.
This product type is highly specialised and rare in industry, it is exclusively for use in environments where there is a risk of explosion, such as packing munitions. In this environment type, there will be no risk of electrocution from malfunctioning electrical equipment (no electrical equipment will be in use) so the standards include no low resistance requirement, only an upper limit to ensure all static is dissipated away from the body.
This footwear type has a resistance of between 1 x 105Ω and 109Ω (100kΩ to 1GΩ) when tested in both “wet and dry” environments. The marking associated with this category of protection is “A” but also forms part of the group marking codes S1, S2, S3, S4 & S5. This is also included in two new marking codes S6 & S7 which are included in the new draft EN ISO 20345/6 & 7:2021
This product type is for use in environments where there is a risk of fire but where the risk of contact with mains electricity cannot be entirely eliminated from the workplace - such as a garage. In these end uses there is some risk of fire or explosion as a result of static discharge, but the risk is relatively low and it will only be in the event of failure of equipment. Antistatic footwear is also suitable where electrical equipment is in use and may pose a risk of electrocution in the event of failure. The antistatic requirements associated with this product type include a low-end electrical resistance to reduce the risk of electrocution in the event of accidental contact with mains voltage electricity. This offers some resistance to current flow through the body, introducing a nominal electrical resistance between the foot and the floor in the event of equipment failure, through the sole and in dry conditions only. Antistatic footwear is NOT suitable for live electrical working.
ESD – Electrostatic Dissipative footwear
The ESD claim often found on footwear does not directly offer protection of the wearer and is therefore not a PPE claim. The ESD claim is entirely about protection of product and therefore outside of the scope of the (European and UK) PPE regulation. Where footwear caries the ESD claim, it can and usually does claim this in addition to the PPE claims which are covered by the CE mark or UKCA mark, these may include either antistatic or conductive.
In recent years, the standard for ESD protection has changed considerably. The test method for ESD footwear can be found in EN 61340-4-3:2018 and the requirements in EN 61340-5-1:2016. There is NO specific marking for this standard but ordinarily some identifying mark will be present on the footwear – often in the form of a Pictogram.
The resistance requirement of the ESD standards for footwear is 1 x 108Ω or less (there is NO lower limit) but this is now carried out in a “very dry” environment at 12%RH, significantly drier than the Antistatic and conductive test methods in the PPE footwear standards.
As there is no lower limit in this test the product does NOT protect the wearer against the risk of electrocution through the failure of electrical equipment. These products are exclusively about the protection of product such as valuable microchips from the risks of overloading from static discharge. They would typically be used for operatives manufacturing circuit boards, computers and similar components
Live electrical working
At entirely the opposite end of the scale is electrical insulation footwear for work on live electrical installations. This is again a highly specialise product type with multiple types and levels available. Products of this type are what is known as “category III PPE” or “complex design” where a failure would result in serious injury or death of the wearer.
The most recent standard for this type of footwear is EN 50321-1:2018 which is really suitable for only Rubber/polymeric moulded footwear. The test is conducted with an inner electrode of water and suspended in a tank of water as the outer electrode. Any product where the upper can be wetted to any degree, such as leather or fabric will invariably fail this testing. This really means that only wellington boot type footwear is available in the EU and UK market offering protection to electricity for work on live electrical installations.
The standards offer 6 levels of performance for use in live working these vary from class “00” (500V AC working voltage), Classes 0, 1, 2, 3 up to class 4 (for working voltages up to 36,000 V AC).
In addition, products can also offer protection against DC working Class 00 (750V DC) and up to Class 2 (25,000 V DC). The products offering protection to both AC and DC voltages are clearly marked with the “AC/DC” identification.
ASTM F2413 Electrical Hazard
In recent years, a worrying trend has been the inclusion of the ASTM Electrical Hazard properties on European/UK PPE products. In the absence of a European/ISO method for footwear with insulating soles and leather/fabric uppers, it is clearly a gap in the claims available. However, this is a conscious decision. While ample electrical insulation can be achieved through the outsole, this alone is NOT considered to be sufficient to protect the wearer working on live electrical installations. Uppers made of leather/fabric may become conductive in contact with water and in the presence of water vapour (Sweat) and the electricity can jump to find the path of least resistance to ground.
It is also very important to note that any marked protection to the ASTM F2413 or other standards are ordinarily outside of the scope of the European/UK certification. i.e. the CE/UKCA marking may or may not apply to the EH claim. Either way, the footwear would need very carefully worded user instructions to explain the significant limitations of this claim to ensure safe working practices.
It is very important that suppliers do not make claims of electrical insulation/live working protection associated with the ASTM “EH” classification on their footwear. The latest version of the ASTM F2413-18 explains clearly why, saying:
Electrical hazard protection is severely deteriorated in wet environments where the protective qualities of the footwear are compromised. Dielectric overshoes should be used.
i.e. the footwear is unsafe for use alone for live working where water/humidity is involved. I cannot stress enough that failure of this PPE or in this case, supply of the incorrect type of product to this end user is likely to be fatal.
Lloyd Preston is technical manager at Tripal Group. For more information, visit www.tripal.global