What is Explosion-Proof Chamber?

On these pages, we often discuss the risks posed to materials and products when exposed to ordinary atmospheres. These include the effects of temperature, humidity, rainfall, and solar radiation.

But not all atmospheres are ordinary. Some are explosive.

Equipment that is intended to operate in potentially explosive atmospheres must pass rigorous tests in explosion-proof chambers.

What is the Explosion-Proof Chamber for?

Let's start with the basics: what is an explosion?

We all know it, but can we define it precisely?

The technical definition for our industry is found in the ISO 8421-1:1987 , which covers the vocabulary of fire-related phenomena. An explosion is defined as "a sudden oxidation or decomposition reaction with a simultaneous increase in temperature, pressure, or both."

It is a chemical reaction that requires three elements to occur: oxygen (air), a flammable material, and an ignition source.

The Explosion-Proof Chamber performs a fundamental test for all products that are found to be working in potentially explosive environments, acting as an ignition source within the triangle. 

Let's see which ones.

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Which sectors are affected by Explosion-Proof Chamber Testing? 

The sectors that are covered by the explosion-proof chamber test must have potentially explosive environments. 

All work environments containing a potentially explosive atmosphere —i.e., containing oxygen, flammable materials, and ignition sources—must comply with the relevant ATEX directives , which include testing in an explosion-proof chamber for all ignition sources.

We will soon talk about the ATEX directives, for now we indicate which activities and sectors are involved:

• chemical and metallurgical industry
• waste disposal industry
• energy production
• civil engineering
• painting
• agriculture

All these sectors have explosive atmospheres and, above all, machinery that must be tested in explosion-proof chambers as it is a potential source of ignition.

What are the Explosion Proof Standards?

As we mentioned, the set of European Union directives regulating equipment intended for use in potentially explosive atmospheres is called ATEX

ATEX has two main classifications: one relating to areas at risk of explosion and one relating to machinery and devices that can act as a source of ignition.

Explosion-proof chamber tests on the latter are outlined in UL 1203, IEC 60079-1:2014 , and CSA C22.2 NO. 30.

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The Explosion-Proof FDM Climate Chamber

What do climate chambers with all this?

With regard to the ATEX directives, climatic chambers are involved in two distinct aspects.

On the one hand, explosion-proof test chambers are climatic chambers, often of the walk-in type for testing large machinery.

On the other hand, all climatic chambers are both potentially explosive environments and potential sources of ignition. For this reason, every climatic chamber must be ATEX certified as an explosion-proof cabinet.

All FDM climatic chambers are ATEX certified and we have discussed it in detail here.

For any further questions or concerns, please do not hesitate to contact us.

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Reference Standards

• ATEX Directive 2014/34/EU — Equipment intended for use in potentially explosive atmospheres. Binding EU reference for manufacturers and users.
• IEC 60079-1:2014 — Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures “d”. Standard for explosion-proof enclosures Ex d.
• IEC 60079-0:2017 — Explosive atmospheres – Part 0: Equipment – ​​General requirements, general requirements on all Ex types.
• IEC 60079-7:2017 — Equipment protection by increased safety “e”, increased safety protection.
• IEC 60079-11:2011 — Equipment protection by intrinsic safety “i”, intrinsic safety for low-energy circuits.
• UL 1203 — Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, North American reference.
• NFPA 70 (NEC) Article 500-506 — National Electrical Code for the classification of U.S. hazardous locations.

Authoritative Sources

• IECEx – IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres. International scheme for Ex equipment certification with global mutual recognition.
• European Commission – ATEX Guidelines. EU Internal Market Directorate, manager of ATEX Directive 2014/34/EU and application guidelines.
• UL Solutions. American reference laboratory for Class I/Div 1-2 certifications according to NEC and UL 1203/913.
• PTB – Physikalisch-Technische Bundesanstalt. German Metrology Institute, the first ATEX Notified Body in Europe and a scientific reference.

Frequently Asked Questions about Blast Proof Chambers

How is the Ex d explosion pressure test performed?

The test verifies that the flameproof enclosure contains the internal explosion without yielding, according to IEC 60079-1 Section 15.The procedure: (1) the enclosure is filled with an explosive gas mixture at the most severe conditions of the group (IIA propane, IIB ethylene, IIC hydrogen/acetylene); (2) ignition with a calibrated electric spark; (3) measurement of the reference pressure with a fast-response piezoelectric sensor (≥ 20 kHz). It is repeated at least 3 times and the maximum value is taken. The hydrostatic test pressure is 1.5x the measured reference pressure (minimum 3.5 bar for IIC), applied for 10-60 seconds without rupture or permanent deformation greater than 0.5%. The non-transmission flame verifies that the internal explosion does not ignite the external atmosphere through flameproof joints: it is performed in an external chamber containing the same mixture with joint spacing reduced to the minimum construction (most unfavorable tolerances). No external ignition is allowed on 5 consecutive tests.

Which gas groups and temperature classes should be considered?

The IEC 60079-0 classification provides three groups for surface industry (non-mining): IIA (less aggressive gases, propane, butane, gasoline), IIB (ethylene, H2S_,diethyl ether), IIC (hydrogen, acetylene, carbon disulfide, the most dangerous due to low MIC – Minimum Ignition Current and MESG – Maximum Experimental Safe Gap). The IIC certification also covers IIA and IIB. The temperature classes limit the maximum surface temperature of the appliance below the autoignition temperature of the gas: T1 ≤ 450 °C (methane, ammonia), T2 ≤ 300 °C (acetylene, butane), T3 ≤ 200 °C (gasoline), T4 ≤ 135 °C (acetaldehyde, ethers), T5 ≤ 100 °C, T6 ≤ 85 °C (carbon disulfide). The full marking is e.g. “Ex d IIB T4 Gb” where Gb = EPL Equipment Protection Level for Zone 1 (gas). For dust, IEC 60079-31 defines IIIA (fibers), IIIB (non-conductive dust), IIIC (conductive such as aluminum, magnesium).

What climatic tests are included in the ATEX certification?

IEC 60079-0 requires, in addition to the specific Ex tests, a set of environmental tests: (1) thermal endurance to heat, aging for 7 days at maximum service temperature (e.g. +80 °C) + 20 K margin; (2) thermal endurance to cold, 7 days at minimum service temperature (-20, -40 or -60 °C) + 5 K margin; (3) thermal shock, thermal shock from T max to 0-5 °C with water; (4) drop test at T min and T max (IEC 60068-2-32) for portable enclosures; (5) IP test according to IEC 60529 with minimum degree IP54 (Zone 1) or IP66/IP67 for outdoor/dust applications; (6) vibration IEC 60068-2-6 for electromechanical structures. These tests are carried out in a climatic chamber with an extended range of -60/+150 °C and an electrodynamic vibrator. Complete documentation includes ATEX Technical File, EU-Type Examination certificate from Notified Body (e.g. IMQ, DEKRA, PTB, LCIE), QA Notification for series production, CE marking + Ex symbol with category (1G, 2G, 3G for gas; 1D, 2D, 3D for dust).

How is an explosion test chamber constructed?

The explosion test chamber is a reinforced pressure vessel made of AISI 316L stainless steel, wall thickness 15-40 mm, designed according to PED 2014/68/EU for peak pressures up to 20-30 bar. The volume varies 0.1-10 m³ depending on the DUT size. Equipped with: (1) gas dosing system with mass flow controller for calibrated mixtures (accuracy ± 0.5% vol); (2) ignition electrodes with calibrated discharge 0.1-10 J; (3) fast response piezoelectric pressure sensors (100 kHz, range 0-50 bar), type K thermocouples for flame temperature; (4) post-test nitrogen inertization system to remove combustibles; (5) armored viewport with multi-layer glass for high-speed observation/filming (10,000 fps). For combined environmental tests, a -40/+100°C diathermic oil thermostating system and humidity simulation are integrated . Safety features include fail-safe emergency buttons, a blast shield, forced post-test ventilation, and SIL2-certified PLC supervision. Installations require a dedicated bunker with reinforced concrete walls ≥ 300 mm.