The human body has an electric resistivity that is sufficiently low to enable it to act as a conductor and, if insulated from earth, it may build up an electrostatic charge.
The charge may be the result of electrification by contact (for example, when walking on an insulating floor or touching charged equipment or materials) or can be generated by induction due to the charge present on clothing or adjacent charged objects.
A troublesome consequence of the electrostatic potential on charged persons is that it may be high enough to create disruptive and dangerous discharges.
Moreover, in many cases the presence of electrostatic charges on a fabric/garment manifests itself in the form of an unpleasant and at times painful electric shock or causes the garment itself to adhere annoyingly to the skin.
In the workplace the phenomenon deriving from the build-up of electrostatic charges can cause greater damage or injury when the charges themselves reach a potential capable of generating an electric arc (environments with the presence of flammable atmospheres, ATEX environments, etc.).
In such cases the wearer must be provided with electrostatic dissipative clothing (falling within the definitions of PPE) and, if deemed appropriate, earthed either directly or by means of conductive footwear and conductive flooring.
The electrostatic properties must be duly certified according to the provisions of Italian Legislative Decree 475/92 (E.D. 89/686/EEC).
The technical standards used to verify the antistatic characteristics of protective clothing are:
EN 1149-1:1995 (*) Protective clothing - Electrostatic properties - Surface resistivity (test methods and requirements )
EN 1149-1:2006 Protective clothing - Electrostatic properties - Part 1: Test method for measurement of surface resistivity
EN 1149-2:1997 Protective clothing - Electrostatic properties - Part 2: Test method for measurement of the electrical resistance through a material (vertical resistance)
EN 1149-3:2004 Protective clothing - Electrostatic properties - Part 3: Test methods for measurement of charge decay
prEN 1149-5:2005 Protective clothing - Electrostatic properties - Part 5: Performance requirements
(*) - Standard replaced by EN 1149-1:2006 and prEN 1149-5:2005