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What are NEC/CSA Hazardous Location Classifications?


What are NEC/CSA hazardous location classifications (e.g. Class I, Division 2)?


The US-based National Electric Code(NEC)) and Canadian Standards Association (CSA) classification systems define product protection categories for explosive environments and hazardous locations. Currently, the following Commtest products are certified for use in hazardous locations:

  • vbSeries instrument models vb5, vb6, vb7, vb8, vbBalancer and vbBalancer+ (only models bearing the CSA logo) for Class I, Division 2, Groups A, B, C and D. Click here to download the CSA certificate for these instrument models.
  • vbOnline permanently mounted instruments (C1D2 models only) for Class I, Division 2, Groups A, B, C and D.

NEC Classifications

Products that have an NEC classification are protected within the environments specified by their classification.

What is a hazardous location?

Hazardous locations are areas where fire or explosion hazards may exist due to the presence of ignitable concentrations of flammable gases or vapors. These locations are grouped according to the properties of the flammable materials that may be present and the likelihood of flammable concentrations.

The NEC and CSA define hazardous locations by class and division.
There are three classes as follows:
Class 1        Locations are made hazardous by the presence of flammable gases, liquids or vapors.
Class 2        Locations are described as hazardous because of the presence of combustible dusts.
Class 3        Locations contain easily ignitable fibers or flyings.
Division refers to the likelihood that ignitable concentrations of flammable materials are present.
Division 1    Designates an environment where ignitable concentrations of flammable gases, liquids, vapors
or dusts can exist some of the time or all of the time under normal operating conditions or
where easily ignitable fibers and flyings are manufactured, handled or used.
Divison 2    Locations are areas where ignitable concentrations are not likely to exist under normal
operating conditions or where Class 3 materials are stored or handled.
Hazardous classes are further defined by groups. Combustible materials are grouped by their relevant physical
properties. These groups include (but are not limited to):
Group A    Acetylene
Group B    Hydrogen
Group C    Ethylene, carbon monoxide
Group D    Propane, gasoline, naphtha, benzene, butane, ethyl alcohol, acetone, methane
Group E    Metals including aluminum, magnesium (Div 1 only)
Group F    Carbonaceous dusts including coal, carbon black, coke
Group G    Dusts not included in E and F including wood, plastics, flour, starch or grain dusts