Bills Technical Journals
Technical Journal #1
Technical Journal #2
Technical Journal #3
Technical Journal #4
Technical Journal #5
Technical Journal #6
Larger projects can include additional “Referees” on the team as additional AHJ Team members like the Fire Marshall, the County Health Dept. Rep, a city Planning Dept. Rep or the School Facilities Manager for schools. For insurance purposes an Insurance Inspector, Insurance Rating Bureau Chief or other Insurance Company Rep. may become AHJ’s on the Team as well.
Technical Journal #7
In NEC Article 500, 501, 502, and 503, Class I, II, and III locations are further broken down into Divisions. The simplified version of a Division for a given Class will be either:
Division 1: The ignitables are significantly present under normal conditions.
Division 2: The ignitables are significantly present under abnormal conditions.
A hazardous location in which ignitables are significantly present in the air in normal conditions in sufficient quantities to be explosive or ignitable, such as petroleum refineries, aircraft hangars, dry cleaning plants, utility gas plants or storage areas for liquefied petroleum or natural gas, and spray finishing areas.
A hazardous location in which ignitables are not normally present in in the air in sufficient quantities to be explosive or ignitable. For example: Closed storage drums containing flammable liquids in an inside storage room would not normally allow the hazardous vapors to escape into the atmosphere. But if one of the storage containers spills over and dumps liquid on the floor, or is old and leaking, you’ve got an abnormal condition.
Spilled flammable liquid
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.
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.
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.
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: