With respect to hazardous (classified) locations, including Class I Group Classifications — only one group has a single chemical listed. This chemical can be very challenging to handle, as it has a minimum igniting current (MIC) ratio of 0.28 and a minimum igniting energy (MIE) of 0.017 mJ. Can you name the group letter designation and chemical?

  1. Group A, Acetylene
  2. Group B, Hydrogen
  3. Group C, Hydrogen Sulfide
  4. Group D, Pentane

Answer: A

The answer can be found in 500.6(A)(1) of the 2008 NEC. As noted in this section of the Code, these requirements also correspond to information presented in NFPA 497, "Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Installations in Chemical Process Areas – 2008 Edition" [497:3.3.5.1.1].

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.