Equipment produced for potentially hazardous atmospheres is marked accordingly. The marking requires certain details depending on the certification and country-specific use.

The marking for electrical equipment is set out in IEC 60079-0. In addition to the name of the manufacturer or their trademark, the type designation, serial number and the test body with certificate number, a special coding is required which describes the intended use of the equipment:

• Ex symbol.
• Symbol of any type of protection (e.g. q) or protection level (e.g. ib) used.
• Equipment Group IIA, IIB or IIC for potentially explosive gas atmospheres and Equipment Group IIIA, IIIB or IIIC for potentially explosive dust atmospheres.
• Temperature class for potentially explosive gas atmospheres and max. surface temperature in degrees Celsius for potentially explosive dust atmospheres.
• Equipment Protection Level (EPL).

The marking for non-electrical equipment is specified in ISO 80079-36. It largely identical to that of electrical equipment. However, instead of various symbols for the protection types, the letter “h” is always used.

In Europe, the marking of electrical equipment in accordance with the IEC standard must meet additional requirements in accordance with ATEX Directive 2014/34/EU and must include the following data:

• Manufacturer's address.
• CE marking (where applicable, with identification number of the notified body).
• Symbol and Equipment Group (e.g. II) as well as Category 1, 2 or 3 and the letter G (gas) or D (dust).

The marking of non-electrical equipment has now been adapted even more closely to that of electrical equipment. In Europe, the EN ISO 80079 series of standards has been applicable since 2016. An "h" is always specified as a symbol for the type of protection.

In addition to the normal data (manufacturer, model, serial number and electrical data), any data relating to explosion protection must be shown on the equipment marking. The specification for this is laid out in the NEC for the USA, in the CEC for Canada and in the relevant building regulations of the test bodies.