First there is the shock wave, then follows the flame: Time is of the essence when it comes to
preventing a catastrophe after an undesirable ignition has taken place inside a plant prone to
explosions. What exactly is involved in this process, and how can risk be averted? IEP
Technologies, the explosion protection expert within the HOERBIGER Group, explains the
critical phase of a dust explosion and how reliable suppression and isolation systems can
save lives. The most important realization is that the first 75 milliseconds are crucial. A
comparison with a blink of a human eye, which lasts an average of 100 milliseconds,
demonstrates just how little time this is.
Due to their relatively large surface, dust and powder particles provide ideal conditions for igniting and
triggering an explosion, regardless of whether flour, wood or coal dust is involved. In an emergency, it
is therefore essential to effectively suppress and isolate the shock wave and combustion in order to
mitigate the risk of an explosion propagating to other parts and leading to uncontrollable detonation.
The reason behind this is that the shock wave of a dust explosion propagates at the speed of sound,
which is approximately 330 meters per second, and the flame at approximately ten meters per second.
Effective suppression is successful when heat is withdrawn from the combustion zone, causing the
temperature to drop below the minimum ignition point of the material.
Successful explosion prevention
What specifically does successful explosion suppression involve? Efforts center around a concept that
is both simple and efficient: Approximately twenty milliseconds after a spark has been ignited inside a
plant, a sensor detects the incipient explosion based on a sudden rise in pressure. Suppressant is
then automatically fed to the source of the explosion nearly instantly, spreads, and absorbs the heat,
stopping the increase in pressure within approximately 75 milliseconds after ignition. As a result, the
explosion is halted and suppressed, without causing major injury to employees or damage to
“This kind of rapid sequence of processes, such as occurs during an explosion, commands substantial
expertise – a basic prerequisite we consistently offer as a full-service provider of explosion protection
solutions,” explains Rudi Post, Managing Director of IEP Technologies in Germany. “In addition to the
high quality of our products and components, it is important to us to offer our customers
comprehensive service that gives them certainty that they have the most effective safety technology
tailored to their needs. This includes not only in-depth advice on-site, but also a comprehensive outline
of all the technical options available to them to save lives and protect assets.”