Classification of explosive and fire-hazardous premises

As a professional explosion-proof equipment & luminaires manufacturer YIBAI LED LIGHTING, below we just talk about some basic knowledge about the classification of explosive and fire hazardous premises.

The main precautionary measure for the prevention of fires and explosions from electrical equipment is the proper selection and operation of equipment in explosive and fire-hazardous areas. According to PUE, the premises are divided into explosives (B-I, B-Ia, B-Ib, B-Ig, B-P, B-Pa) and fire-hazardous (B-I, P-P, P-Pa, P- W) zones.

The explosive zone is a space in which explosive mixtures are or may be present

The fire zone is a space where combustible substances can be present during the normal technological processes and in case of possible violations thereof.

Class B-I – Areas of premises in which flammable gases and vapors are emitted in such quantity and with such properties that they can create explosive mixtures with air or other oxidants under normal short operating modes.

Class B-Ia – Areas of premises in which an explosive concentration of gases and vapors is possible only by accident or malfunction.

Class B-Ib are the same zones as Class B-Ia but have the following features:

  • combustible gases have a high lower concentration limit of flame spread (15% or more) and a sharp odor;
  • in the event of an accident in these areas, only local formation is possible! explosive concentration, which extends to a volume not exceeding 5% of the total volume of the room (zone);
  • flammable gases and liquids are used in small quantities without the use of open flames, in exhaust hoods, or under exhaust umbrellas.

According to PUE, if the volume of the explosive mixture exceeds 5% of the free volume of the room, then the whole room belongs to the corresponding class of explosives. If the volume of the explosive mixture is equal to or less than 5% of the free volume of the room, then the area of ​​the room within 5 m horizontally and vertically from the technological apparatus from which the release of combustible gases or steam of LZR is possible is considered explosive. Premises outside the explosive zone shall be considered explosive unless there are other factors that create an explosion hazard.

Class B-Ig – External installations containing explosive gases, vapors, liquids, the explosive concentration of which can be formed only by accident or malfunction.

Class B-II – Areas of premises where the formation of explosive concentrations of dust or fibers with air or other oxidizing agents may occur under normal, short operating conditions.

Class B-IIa – Areas similar to those of Class B-IIa, where explosive concentrations of dust and fibers can be generated only by accident or malfunction.

Class P-I – Areas of premises in which flammable liquids with a flashpoint above 61 ° C are used or stored.

Class P-II – Areas of premises where combustible dust or fibers with a lower concentration limit of the flame spread of more than 65 g / m3 of air volume or explosive dust are emitted, the contents of which do not reach explosive concentrations in the air of the premises.

Class P-IIa – Areas of rooms containing solid or fibrous combustibles. Combustible dust and fibers are not released.

Class P-III – External installations where flammable liquids with a flashpoint above 61 ° C are used or stored, as well as solids.

The zone class is determined by the technologist together with the electricians of the design or operational organization, based on the environmental characteristics.

According to the PUE, closed-loop electrical equipment is used in fire-hazardous areas, the interior of which is separated from the outside by a shell. Control and protection equipment, luminaires are recommended to be used in dustproof versions. All wiring must have sound insulation. Explosion-proof equipment manufactured in accordance with GOST 12.2.020-76 shall be used in hazardous areas and in external installations. Starting equipment, magnetic actuators for Classes B-I and B-II must be carried out outside of explosive rooms with remote control. Wires in explosive areas must be laid in metal pipes. The armored cable may be used. Luminaires for Classes B-I, B-II, B-IIa must also be explosion-proof.


Our company as one of the best LED lights manufacturers mainly focuses on the Europe & North American market, the main product includes, LED high bays, low bays, canopy lights, shoebox lights, wall packs, gas station lights, lamp accessories, and LED modules, football lights, etc…as a leader in manufacturing and marketing of LED lighting. For providing a high-quality manufacturing environment and professional lighting assembly, we introduced many SMT automated production lines & advanced equipment and have the ability to do OEM/ODM orders. Please feel free to contact us if you are interested in our products and hope we could cooperate with each other and create a bright future for our business.

For more information about YIBAI LED lighting solutions for tennis court lighting systems including IES files, Dialux simulation reports, and technical datasheets, please visit

Contact Us: Guangdong Yibai Optotech Co., Ltd

Tel: +86-13631786201

E-mail: [email protected]

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