Blast-Resistant Door: Understanding EN 13123 / EN 13124 Standards and EXR Classes

A blast-resistant door is a door engineered to withstand the shock wave and overpressure generated by a deflagration, in order to protect people, equipment, and the operational continuity of an exposed building. Its resistance is assessed at European level through standards EN 13123 (requirements and classification) and EN 13124 (test methods), with resistance classes ranging from EXR1 to EXR5. This is a critical performance requirement for sensitive sites: energy infrastructure, chemical and petrochemical industries, data centres, embassies, command posts, military installations, and defence buildings.

Why Protect a Building Against Explosion?

Within a physical security and counter-terrorism approach, a door does not merely close or control access: it can absorb part of the blast effect, compartmentalise a risk zone, and preserve a strategic access point. Blast-resistant doors address three families of threats: anti-blast (pressure wave), explosion proper, and breaching (charge applied in contact or in close proximity to the door leaf).

European Standards EN 13123 / EN 13124

Two series of standards coexist depending on the explosion scenario under consideration.

EN 13123-1 / EN 13124-1 — Shock tube test. This method simulates distant explosions with large charges: from 100 to 2,500 kg of TNT at distances of 35 to 50 m. It yields a classification of EPR1 to EPR4.

EN 13123-2 / EN 13124-2 — Free-field test (arena test). This is the reference method used by Heinen: the door is subjected to a real explosion under controlled conditions, with charges of 3 to 20 kg of TNT at 3 to 5 m. It yields a classification of EXR1 to EXR5.

In summary: EN 13124 defines the test methods; EN 13123 defines the requirements and assigns the resulting resistance class.

International Sector Standards

PIP STC01018 — American petrochemical standard. It is based on calculations derived from coefficients obtained through real-world tests and defines three damage levels: LOW, MEDIUM, and HIGH.

UFC 3-340-02 — Global military standard. Design guide from the US Department of Defense, based on dynamic calculations and decades of actual explosive testing.

The distinction between EPR and EXR is fundamental to correctly interpreting a specification, and it is frequently misunderstood.

EPR corresponds to larger charges at greater distances. The peak pressure is relatively low, but the impulse is high. This is the typical scenario of an accidental industrial explosion or a long-range attack.

EXR corresponds to smaller charges at close range. The peak pressure is high, but the impulse is short. This is the scenario of a breaching attempt or a charge placed in immediate proximity to the door leaf.

An important physical point: peak pressure decreases faster than impulse with distance. At long range (EPR), impulse therefore dominates; at short range (EXR), instantaneous pressure is the prevailing factor.

Minimum values for EPR classes (EN 13123-1):

Note: the duration of the positive phase (t+) must not be less than 20 ms.

Values for EXR classes (EN 13123-2):

Conversion note: 1 bar = 14.504 psi = 100 kPa = 100 kN/m² ≈ 10 t/m²

Pressure represents the maximum intensity of the force exerted by the shock wave at any given instant.

Impulse accounts for the duration over which that pressure is applied.

A very violent but very brief shock (high pressure, low impulse) does not produce the same effects as a less intense but sustained push. Pressure primarily causes sudden deformation; impulse places greater demands on the anchoring system. A rigorous specification therefore integrates both parameters.

The Dynamic Nature of an Explosion

An explosion always has a dynamic character, fundamentally different from a static load. A shock wave reaches its peak pressure within a few milliseconds, decays very rapidly, and then reverses: the door is successively pushed by a positive pressure phase, then pulled by a negative pressure phase.

Heinen carried out a series of tests together with the company BS&A at an open-air firing range, under free-field test conditions (arena test).

 
Key point for specification — for an identical configuration, performance drops from EXR3 to EXR1 depending on the exposure direction. The likely direction of the shock wave must therefore be treated as a design parameter in its own right, to be factored in from the specification stage on the same footing as the targeted threat level.
Classes tested: EXR1, EXR2, EXR3 · Single and double doors · Each configuration tested in both exposure directions.
Note: Heinen Doors has not yet obtained certification. This is currently in progress.

• High-risk industry: chemical and petrochemical sites (PIP STC01018)
• Energy: nuclear and thermal power plants, critical infrastructure
• High security: embassies, command posts, military sites (UFC 3-340-02)
• Infrastructure: data centres, underground transport structures