The Hindenburg disaster (May 6, 1937, Lakehurst, USA) was not a classical explosion, but primarily a rapidly spreading fire that engulfed the airship within seconds.

What Actually Happened?

The German airship LZ 129 Hindenburg was filled with hydrogen, a highly flammable gas. During the landing maneuver:

• an electrical spark or electrostatic discharge likely occurred
• leaked hydrogen formed a flammable hydrogen–air mixture
• the hydrogen ignited

Within seconds, flames spread across the entire airship structure.

Explosion or Fire?

Technically speaking: 1) It was not a detonation 2)It was a very rapid hydrogen combustion (deflagration), because the burning process was extremely fast and involved a very large structure, witnesses perceived it as an explosion. In reality, it was a rapidly spreading fire that destroyed the airship in about 30–40 seconds.

Why Did It Look Like an Explosion?

Several factors contributed to the dramatic appearance:

1. Hydrogen burns extremely fast.
2. The airship was enormous (245 meters long).
3. The outer skin and structural materials ignited quickly.

Therefore the event appeared explosion-like, even though no classical blast wave was produced.

A Remarkable Technical Detail (From an Explosion Protection Perspective): modern research suggests that the initial ignition may not have started with hydrogen, but rather with the outer coating of the airship.

The coating contained:

• aluminum powder
• iron oxide

This combination made the surface highly flammable. A static discharge could have ignited the coating first, after which the hydrogen rapidly caught fire.

Why the Hindenburg Disaster Is Important for Explosion Protection?

The Hindenburg accident demonstrates several fundamental principles that today form the basis of ATEX Directive 2014/34/EU and IECEx System safety philosophy.

1️⃣ Flammable Atmosphere + Ignition Source = Disaster

Hydrogen has two critical properties (besides others):

• Very low ignition energy (~0.02 mJ)
• Extremely wide flammable range (4–75% by volume)

A likely sequence of events:

1. hydrogen leakage from gas cells
2. formation of a hydrogen–air mixture
3. electrostatic discharge
4. rapid combustion / fire

This perfectly illustrates the explosion triangle: presence of fuel, oxidizeR and ignition source.

2️⃣ Static Electricity – An Underestimated Ignition Source

During landing, the airship likely accumulated electrostatic charge. When the mooring lines touched the ground:

• a potential difference formed
• a discharge could occur

For this reason, modern hazardous-area installations require:

• grounding
• equipotential bonding
• antistatic materials

3️⃣ Material Selection Risks

The airship's outer coating contained aluminum powder and iron oxide, which made it highly flammable and capable of sustaining intense combustion. This illustrates a key engineering lesson: A system can become dangerous due to non-obvious material properties.

Today this is addressed through:

• material compatibility assessment
• surface treatment evaluation
• certification of equipment used in hazardous areas

4️⃣ Energy Carrier Selection Matters

The choice of hydrogen was largely a political and economic compromise. A safer lifting gas, Helium, was available but could not be obtained because the United States restricted its export at the time.

5️⃣ Lack of Structured Hazard Analysis

Today, a system like this would require extensive safety studies, such as:

• PHA (Process Hazard Analysis)
• HAZOP
• risk assessment
• ignition source analysis
• hazardous area classification

In 1937, such systematic safety methodologies did not yet exist.

6️⃣ Deflagration vs. Detonation

The event was a deflagration, not a detonation.

Phenomenon	Characteristics
Deflagration	Flame front slower than the speed of sound
Detonation	Supersonic combustion with a shock wave

The Hindenburg burned for about 30 seconds, which is consistent with rapid gas combustion, not detonation.

Key Explosion Protection Lessons

The Hindenburg disaster clearly demonstrates that:

1. flammable gases + leakage = explosive atmosphere
2. static electricity can be a critical ignition source
3. material selection plays a major safety role
4. lack of hazard analysis creates systemic risk
5. what appears to be an "explosion" may actually be rapid combustion

An Ex protection paradox today:

If the Hindenburg were designed according to modern ATEX principles, the classification would likely be:

• Zone 1 inside the gas cells
• Zone 2 in the surrounding environment

Keep up the good work!

Arpad
veress@exprofessional.com