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#8
 What Fire vs Explosion?
It matters with HazLoc Groups.
There can be two different types of catastrophic events in areas classified as hazardous locations.
There can be Fires, which are purely chemical reactions that release heat during the combustion process.

And there can be Explosions, which release a large amount of energy in a very short period of time, often accompanied by a rapid expansion of volume.
Why is this important to the classification of Hazardous Locations?
The temperature where a material burns is important to know, and a scale can be created of the relative flammability of different materials.

There are many different materials, vapors and gases that create other different types of risk for a building. These materials are categorized based on the potential risk they pose for the creation of an explosion – and they are also categorized as to how big or how violent an explosion that can result, IF they exploded.

The temperature where a material burns is important to know, and a scale can be created of the relative flammability of different materials.

There are many different materials, vapors and gases that create other different types of risk for a building. These materials are categorized based on the potential risk they pose for the creation of an explosion – and they are also categorized as to how big or how violent an explosion that can result, IF they exploded.
And, YES – there are different types of explosions, and the extremes might be imagined as a July 4th fire-cracker at one end of the spectrum, and an atomic bomb being at the other end.
 
Fires and Explosions have rating systems, and these two phenomena are related in a way - Fires can also result from explosions, and explosions can result from fires.
The major distinction between Fire and Explosion is the rate of energy release. Fire releases energy relatively slowly when compared to explosions, which release energy rapidly, typically in thousandths of a second (microseconds).
But the key difference is the rate of the release of energy. For example, compressed air within a balloon contains energy. If the energy is released slowly through the balloon air stem, the balloon is harmlessly deflated - but if the balloon pops suddenly and all the energy within the compressed balloon releases at once, the result becomes a small explosion.
So - What is an Explosion?
An Explosion is a rapid expansion of gases resulting in a rapidly moving explosion pressure or shock wave. This is technically called Explosion Pressure . Explosion damage is caused by this shock wave, which can travel at super-sonic speeds (faster than the speed of sound: 1,087 feet per second). The explosive pressures of different gases and dusts can be measured and used to categorize different materials.
And taking all of this back to the world of Hazardous Location classifications, realize that this is how the “Groups” of materials, vapors and gases are created. There will be more covered on different types of “Groups” later - in future Journals, but the important point here is that “Groups” are created based on:
  1. Their flammability and
  2. The severity of the explosion they can create.
Bill Nagengast, President and Lighting Engineer, Solas Ray Lighting, holds over 20 patents in the lighting industry.
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TJ-8 1.12.17