When is an explosion really an explosion, take two

A few weeks back, we had a letter to the editor in C&EN that took us to task for using “blast” and “explosion” to describe two industrial incidents. We have more in this week’s issue (which, I might add, is a particularly awesome one in celebration of C&EN’s 90th anniversary). The consensus? The rupture of a nitrogen line is a mechanical explosion, and C&EN used the words appropriately. Here’s what our readers said:

Regarding Richard Rosera’s letter “Choosing the Right Words,” explosion is the correct term (C&EN, Aug. 5, page 4). The definition of the word explosion is the rapid expansion of a gas.

To quote Rosera, the case at hand was “caused by the rupture of a nitrogen line or vessel by overpressure.”

Rob Kovacich
Hood River, Ore.

Recalling my years dealing with hazard evaluation led me to question Rosera’s letter. An explosion is defined as the rapid increase in volume and release of energy in an extreme manner. Or, as Frank T. Bodurtha explains in his book “Industrial Explosion Prevention and Protection,” “an explosion is the result, not the cause, of a rapid expansion of gases. It may occur from physical or mechanical change.”

Thus, the rupture of a nitrogen line or vessel does indeed result in an explosion, as does the rupture of an overfilled tire.

Robert G. Robinson
Lawrenceville, N.J.

As a chemistry educator and professional pyrotechnician, I answer myriad questions regarding explosions. If the term explosion is used to refer to “the rupture of a nitrogen line or vessel by overpressure,” it is more specifically a mechanical explosion, but it’s an explosion nonetheless.

The criticism leveled by Rosera is unwarranted. Both the mainstream press and C&EN are correct in addressing the CF Industries accident as an explosion. Although physical failure of materials containment may be due to either chemical or mechanical reasons, the result is still an explosion.

Kathleen Holley
Arlington, Texas

At the time of the original news story, the cause of the explosion at a Williams C. ethylene plant in Geismar, La., was unknown. A July 31 story in the New Orleans Times-Picayune indicates that it was still unknown by that time. I can’t find anything more recent, but the U.S. Chemical Safety & Hazard Investigation Board is investigating it, so we’ll have an answer eventually. The incident killed two workers.

Author: Jyllian Kemsley

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2 Comments

  1. Without doubt, Rosera was likely referring to a more specific and no less valid word usage of the word “explosion,” namely, “the process by which something is deliberately made to explode,” as in cases of criminal intent.

    The word “explosion”–particularly in today’s world–carries connotations that go considerably beyond mere scientific descriptions.

    If chemistry is to truly interface with the public, this raises a question: To what extent does chemistry have a corner on word usage?

  2. It is important to note that a BLEVE need not be a chemical explosion – there does not need to be a fire – however if a flammable substance is subject to a BLEVE it may also be subject to intense heating, either from an external source of heat which may have caused the vessel to rupture in the first place or from an internal source of localized heating such as skin friction . This heating can cause the substance to ignite, adding a secondary explosion caused by the primary BLEVE. While blast effects of any BLEVE can be devastating, a flammable substance such as propane can add significantly to the danger.