As with plant, it is equally important to ensure that personnel in hazardous areas are suitably earthed at all times.  The most practical way to achieve this is to ensure that static dissipative footwear is worn and that floors have a suitable level of conductivity.

Several standards are in use, the most commonly adopted being the safety footwear standards, EN ISO 20345 (Europe) and ANSI Z41 SD type II (USA).  Both recommend an upper limit for static dissipation of 1 x 10^9 Ohms.  The alternative level of 1 x 10^8 Ohms, as descirbed in CLC/TR 50404 and BS5958 is occasionally used; however, it is more difficult to obtain this type of footwear.

In order to comply with the recommendations, a footwear tester should be used.  It is vital to ensure that the tester selected monitors to the same level as the footwear in use on site.  Testers monitoring to the levels recommended for use in the electronics industry (ESD) should not be used for testing the integrity of EN ISO 20345 or ANSI Z41 SD Type II footwear.

An optional volt-free interlock contact is available to control a door entry mechanism, to prevent access to hazardous working zones unless the correct specification footwear is worn, or alternatively to interface with alarms/sounders or data collection systems.

EN ISO 20345 states that the footwear .... should normally have an electrical resistance of less than 1000 Megohm (1 x 10^9 Ohms) at any time throughout its useful life.  The user is recommended to establish an in-house test for electrical resistance and use it at regular and frequent intervals (7.2).

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