In the United States, the path that led to the development of equipment suitable for use in areas at risk of explosion has followed an almost parallel path to Europe, addressing the issue first in the mining industry and then extending it to electrical devices in the NEC. The use of still current techniques demonstrates how much the more traditional methods of protection can boast a history of reliability and safety spanning more than a century.

The most used entry systems are: entry with sealing fitting, cable entry with Ex barrier cable gland, cable entry with Ex cable gland with sealing ring. When we talk about electrical systems with electrical cable installation, entries are made using a cable gland, which can be of two types: barrier or with sealing ring.

In areas at risk of explosive atmospheres, systems with electrical cable installations are nowadays a valid alternative to traditional systems with conduits systems. Their diffusion has been driven by the increasing presence of increased safety equipment such as junction boxes or 'Ex eb ' lighting fixtures, which implicitly lead to the need for sections of the system with cable installation.

Today we define the methods of protection as techniques that are made available to us by harmonized standards, to satisfy the Essential Health and Safety Requirements. It appears clear how the first decades of the twentieth century proved to be fundamental for the development of the techniques underlying the current methods of protection.

Nowadays, the classification in an area at risk of explosion concerns many sectors of the industry and includes the use of the most diverse equipment. This great variety of devices and applications must not make us forget that the origin of explosion risk containment techniques lies down there, in those dark mines where it all began.

The 'Ex d' type of protection, now referred to as 'Ex db', is based on a simple theoretical concept: containment by means of a sturdy casing and flame retardancy. Its success is due to this simplicity, it is in fact one of the first methods of protection developed in the mining industry and still today it is one of the most widespread in areas classified for potentially explosive atmospheres.

ATEX device's manufacturers use different types of protection to achieve a certain EPL. These methods of protection are constantly evolving both technical and regulatory. In any case, the most used are those that have established themselves historically.