Explosive environments – classification plan and explosion protection document

When flammable products are handled, there is always a risk of an explosive atmosphere (explosive environment) forming. “Explosive atmosphere” means a mixture of gas or vapour with air in a concentration that enables it to ignite. The risk of a potentially explosive environment forming must always be assessed in a risk assessment under the ATEX Directive (99/92/EC and 2014/34/EU). In Swedish legislation, the requirements under the ATEX Directive have been incorporated into the Swedish National Electrical Safety Board’s regulations on electrical equipment for potentially explosive environments (ELSÄK-FS 2016:2), the Swedish Work Environment Authority's regulations on equipment for potentially explosive atmospheres (AFS 2016:4), and the Swedish Work Environment Authority's regulations on work in potentially explosive environments (AFS 2003:3). The potentially explosive environment also includes adjacent areas where a hazard could occur due to the explosive atmosphere. The results of the work are summarised in a classification plan (SRVFS 2004:7). Please note that an explosive atmosphere can form even when small quantities of a flammable substance are mixed into the air.

The main principle for hazardous area classification is to divide the areas into different zones depending on how the flammable substances are handled in the area.

Zones are defined as follows:

• Zone 0: An area in which explosive gas mixture is always expected to be present, e.g. inside a tank of flammable solvent.
• Zone 1: An area in which explosive gas mixture is expected to occur to a limited extent during normal operating conditions, e.g. at a filling station for flammable products.
• Zone 2: An area in which the presence of explosive gas mixture is unlikely under normal operating conditions and, if it occurs, is rare and very short.

If the classification plan shows that an explosive atmosphere could occur, the protective measures that need to be taken must be documented in an explosion protection document. The information to be included in the explosion protection document is detailed in the Swedish Work Environment Authority’s regulations on amendment of the Swedish Work Environment Authority’s regulations (AFS 2003:3) on work in potentially explosive environments (AFS 2014:13), Section 7. Each zone has different requirements for reducing the risk of an explosive atmosphere forming and for reducing the risk of ignition. There are various measures that can be taken to reduce the risk of an explosive atmosphere forming. If it is not possible to replace the substance that could create an explosive atmosphere, measures must be taken to minimise the extent to which the substance comes into contact with air or to ensure adequate ventilation.

If it is not possible to limit the formation of an explosive atmosphere, it is important to reduce ignition sources. There are many different ignition sources which can ignite an explosive atmosphere, e.g. flames and hot gases, mechanical sparks, electrical sparks and static electricity. Generally speaking, all forms of energy transfer can pose an ignition hazard. Examples of measures to reduce ignition are prohibition of open fire, protective earthing, use of appropriate workwear, avoidance of conductive objects, use of spark-free tools, and use of Ex equipment.