Explosion protection guide

In many industries, flammable and other hazardous substances are used every day, which have to be extracted in the production process or to keep the workplace clean. These include, for example, flour and sugar in the food industry, light metal powder in aluminum processing, sharp-edged chips, grinding dust and combustible dust in the automotive industry and many more. If the relevant substances are present in the air (oxygen) in a certain concentration, there is a risk of explosion from an ignition source, for example a vacuum cleaner. For the protection of employees, systems and the environment, the topic of explosion protection is therefore indispensable in these areas - because an explosion can have devastating consequences. Numerous directives provide assistance to operators of systems on the one hand and manufacturers of devices used in these areas on the other with explosion protection measures. The corresponding measures include, among other things, that explosion-proof industrial vacuum cleaners must be used to extract these (or other) substances in an explosive environment. KRAHNEN offers appropriate solutions for this with explosion-proof industrial vacuum cleaners. Find out more about explosion protection in our guide below. In our FAQ we provide answers to frequently asked questions and thus offer you an introduction to the important and complex topic.

FAQ on explosion protection

What is an explosion?

An explosion is a sudden, rapid reaction of oxidation or decomposition that produces high temperature, high pressure, or both. Explosions often occur when combustible gases, vapors or dust are combined with the oxygen in the air.

How does an explosion occur?

An explosion usually occurs when three factors come together: a combustible material, oxygen from the air, and an ignition source. The combustible substance and oxygen must be present in an appropriate proportion to create an explosive atmosphere that can then be ignited by an ignition source. Flammable substances include gases, liquid vapors and dusts. In work and production sites, ignition sources can have very different origins, such as devices, tools, systems and more. This can include hot surfaces, flames, sparks, static electricity and more. These sources of ignition can occur on or through equipment such as tools, machines or devices.

What is explosion protection?

When it comes to explosion protection, a distinction is made between primary, secondary and tertiary explosion protection. Primary explosion protection includes all measures that either reduce or completely replace the amount of combustible material or the amount of oxygen. This means that the formation of an explosive atmosphere is prevented.

If an explosive atmosphere can develop despite primary explosion protection measures, the ignition of this atmosphere must be prevented. This is what secondary explosion protection deals with. with e.g. B. Types of protection according to the protection level, sources of ignition on devices and systems (equipment) are avoided. In order to specifically define the level of protection for devices, potentially explosive areas must be divided into zones based on parameters such as the frequency and duration of the occurrence of a hazardous explosive atmosphere. In addition, it is important to know the explosion-related parameters of the combustible materials involved and the local environmental conditions. Operators, equipment manufacturers and installers alike can use the explosion-related parameters to identify the respective danger precisely, produce the appropriate equipment for it and select the right devices for the respective danger and the respective area.

If both the primary and secondary explosion protection are not sufficient, protective measures must be taken that limit the effects of an explosion or reduce it to a harmless level. Examples of so-called tertiary explosion protection - also known as constructive explosion protection - include explosion-proof construction of containers and apparatus, explosion pressure relief, explosion suppression and prevention of explosion transmission.

Where can I find the guidelines for explosion protection?

On an international level, guidelines for explosion protection can be found in IEC/ISO standards, on a European and German level in EN/DIN EN standards. The international, European and German standards regarding explosion protection are harmonized because the relevant standard documents are the same in terms of content and registration number. Both electrical and non-electrical devices are developed and tested according to IEC/ISO standards and then certified with the IECEx CoC certificate of conformity. However, the acceptance of certificates is based on regional and local legal and insurance regulations. In the case of international projects, specifications with regard to the requirements for explosion protection must therefore be clarified individually.

Binding, uniform quality requirements for explosion protection of devices, components, etc. are created with the ATEX product directive 2014/34/EU, which are underpinned by harmonized EN standards of the CENELEC and CEN standards organizations. The directive was initiated by the EU and its predecessor organizations to harmonize the European internal market and arose from numerous non-harmonised national regulations.

The ATEX product directive 2014/34/EU defines rules for placing products on the market that are used in potentially explosive atmospheres. It applies to both electrical and non-electrical devices (and components) that can also become an ignition hazard. The main focus of the directive, unofficially known as the ATEX product directive, is the protection of people in potentially explosive areas. It specifies the basic health and safety requirements to be observed by equipment manufacturers such as special explosion-proof industrial vacuum cleaners. It must also be possible to prove these requirements by means of appropriate conformity assessment procedures. Within the ATEX product directive 2014/34/EU, the relevant devices and components are divided into different device groups. Each device group is assigned to at least one specific zone, for example the gas area (zone 1,2) or the dust area (zone 21,22), in which the may be used. In addition, the guideline prescribes temperature classes (T1-T6) into which the devices are classified. This defines the maximum surface temperature that a device/equipment may develop so that the respective explosive mixture in which the device is used cannot ignite.

In addition, the ATEX company guideline 1999/92/EG defines the minimum regulations for improving the health protection and safety of employees who can be endangered by an explosive atmosphere. This includes, for example, that the operator or employer must implement primary, secondary and tertiary explosion protection measures - i.e. also provide appropriate equipment such as explosion-proof industrial vacuum cleaners and other cleaning products for safe cleaning in Ex zones. For a risk assessment of the company, the employer must create an explosion protection document in which all areas with a potentially explosive atmosphere are divided into clearly defined zones. A distinction is made between zones with an explosive atmosphere of air and combustible gases, vapours, mist (zone 0,1,2) and combustible dust in the air (zone 20,21,22).

The combination of both ATEX directives creates a closed system that prevents explosions in order to protect people, the environment and property.

What dust explosion classes are there?

The basis for a dust explosion is a certain mixing ratio between oxygen and dust particles of different sizes. As soon as a certain dust density is reached and the particle size falls below a certain level, an explosive atmosphere is created which can then be ignited by an ignition source. In order to pursue protection concepts in connection with dust explosions and to correctly design measures of constructive (tertiary) explosion protection - for example for an explosion-proof design of containers - combustible dusts are divided into explosion classes according to their KSt value. This is the maximum pressure increase over time related to a volume of 1 m3. There are three different dust classes, which are divided as follows:

Dust explosion class

KSt-Wert (in bar · m · s-1)

St 1

>0 to 200

St 2

>200 to 300

St 3


Constructive protective measures for explosion pressure relief or explosion suppression on equipment are then designed according to the determined dust explosion class.

What types of protection are there?

Only explosion-proof devices may be used in areas with a potentially explosive atmosphere. These devices are designed with different types of protection: the basic aim here is to avoid the risk of an explosion if both an explosive atmosphere and an ignition source are present at the same time (secondary explosion protection). The type of protection indicates how an ignition source can be avoided, for example through appropriate design and construction conditions. The types of protection are defined according to international and European standards. The types of protection for electrical devices are defined in the series of standards EN IEC 60079, the types of protection for non-electrical devices in the series of standards DIN EN ISO 80079 and DIN EN 13463. The type of protection used in the manufacture of a device depends on its function and type.

Some types of protection are available in different protection levels. These correspond to the device categories according to Directive 2014/34/EU or the device protection levels EPL according to IEC 60079-0. The more explosive the environment, the higher the type of protection must be selected. For all types of protection against ignition, the parts of the devices that are in the potentially explosive atmosphere or that have access to the respective parts must not reach impermissibly high temperatures.

The following types of protection are available:

for electrical equipment in a gas atmosphere

  • Intrinsic safety Ex i
  • Flameproof enclosure Ex d
  • Increased safety Ex e
  • Pressurized enclosure Ex p
  • Oil immersion Ex or
  • Encapsulation Ex m
  • Sand filling Ex q
  • Type of protection for Zone 2 Ex n
  • Special type of protection Ex s

for electrical equipment in a dusty atmosphere

  • Pressurized enclosure Ex pD
  • Intrinsic safety Ex iD
  • Encapsulation Ex mD
  • Protection by housing Ex tD

for non-electrical equipment

  • Protection through vapor-inhibiting encapsulation Ex fr
  • Flameproof enclosure Ex d
  • Intrinsic safety Ex g
  • Constructive safety Ex c
  • Ignition source monitoring Ex b
  • Pressurized enclosure Ex p
  • Liquid immersion Ex k

What is the device protection level?

Potentially explosive areas are divided into different zones. The devices, on the other hand, which are to be used in potentially explosive areas, are tailored to the different zones and their hazard potential. For this purpose, the explosion-protected devices are classified according to EU Directive 2014/34 (ATEX) in device categories and at international level according to IEC 60079-0 in device protection levels EPL (Equipment Protection Level). Devices for hazardous areas are categorized into three levels of protection. A distinction is made between gases, vapors and mist (letter G for gas) and dust (letter D for dust).

Devices with the EPL Ga/Da protection level must be designed in such a way that they provide a very high level of safety. Even in the case of rare malfunctions, there is no risk of ignition on the devices. They can be used in zones 0/20.

Devices with the protection level EPL Gb/Db must ensure a high level of security. Even in the event of normal malfunctions, the devices must avoid sources of ignition. They can be used in zones 1/21.

Devices of protection level EPL Gc/Dc must ensure a normal level of safety and avoid sources of ignition in normal operation. They can be used in zones 2/22.

What is electrical explosion protection?

Electrical explosion protection dates back to the 19th century, when electrical engineering found its way into industry and households, but at the same time explosive atmospheres due to methane and coal dust were present in hard coal mining. From then on, ways and means were sought to be able to use electrical equipment (potential sources of ignition) in explosive atmospheres without causing an explosion. This has resulted in explosion-proof electrical equipment that is classified into types of protection. The precise requirements for electrical equipment in terms of the resulting so-called electrical explosion protection are specified in accordance with international IEC/ISO standards and European CEN/CENELEC and DKE/DIN standards with register number 60079.