Hazardous area sensors

UNITED STATES — FACTORY MUTUAL (FM)
Division 1, Classes I, II, III, Groups A, B, C, D, E, F, and G

In the United States, Article 500 of the National Electrical Code (NFPA 70) defines the following divisions:

Division 1 Hazardous concentrations of flammable gases, vapors—or combustible dusts in suspension—continuously, intermittently, or periodically present under normal conditions.

Divsion 2 Volatile flammable liquids or gases are present, but are normally confined within closed containers or the flammable vapors are normally prevented by positive mechanical ventilation and from which they can escape only under abnormal operating or fault conditions. Combustible dusts are not normally, nor likely, to be thrown into suspension.

Following are typical flammable gases, vapors, mists and ignitable dusts, fibers and filings. They are classified according to the spark energy required to ignite the most easily ignitable mixture with air.

• Class I
  • Group A Acetylene
  • Group B Hydrogen
  • Group C Ethylene
  • Group D Propane
    
• Class II
  • Group E Conductive Dust (metal dusts)
  • Group F Carbonaceous Dust (coal dusts)
  • Group G Non-Conductive Dust (grain dusts)
    
• Class III
  • Fibers
  • Flyings (material larger than dust that are not normally in suspension in air)

CANADA — CANADIAN STANDARDS ASSOCIATION (CSA)
Division 1, Class I, Groups A, B, C, and D

In Canada, Section 18 of the Canadian Electrical (Code C22.1), the standards are similar in concept to the United States standards although different procedures are used to match a barrier to a hazardous area instrument.

UNITED KINGDOM & EUROPE
Zones 0-2, Groups I, IIA, IIB, IIC

In Europe, CENELEC standard EN 50 014 defines the following zones:

• Zone 0 Hazardous gas atmosphere is continuously present or is present for long periods of time (ia apparatus only)
• Zone 1 Hazardous gas atmosphere is likely to occur during normal operation (ia or ib apparatus only)
• Zone 2 Hazardous gas atmosphere is not likely to occur during normal operatings, or will only occur for short periods of time (ia or ib apparatus only)

Following are typical flammable gases, vapors, and mists. They are classified according to the spark energy required to ignite the most easily ignitable mixture with air.

• Group IIC Acetylene, Hydrogen
• Group IIA Propane
• Group IIB Ethylene
• Group I Methane (firedamp)

AUSTRALIA—SAFETY IN MINE TESTING & RESEARCH STATION
Zones 0-2, Groups I, IIA, IIB, IIC

In Australia, the standards are similar in concept to the European CENELEC standard EN 50 014, which defines the following zones:

• Zone 0 Hazardous gas atmosphere is continuously present or is present for long periods of time (ia apparatus only)
• Zone 1 Hazardous gas atmosphere is likely to occur during normal operation (ia or ib apparatus only)
• Zone 2 Hazardous gas atmosphere is not likely to occur during normal operatings, or will only occur for short periods of time (ia or ib apparatus only)

Following are typical flammable gases, vapors, and mists. They are classified according to the spark energy required to ignite the most easily ignitable mixture with air.

• Group IIC Acetylene, Hydrogen Group IIA Propane
• Group IIB Ethylene Group I Methane (firedamp)

FRANCE—INSTITUT NATIONAL DE L’ENVIRONNEMENT INDUSTRIEL ET DES RISQUES
Zones 0-2, Groups I, IIA, IIB, IIC

In Europe, CENELEC standard EN 50 014 defines the following zones:

• Zone 0 Hazardous gas atmosphere is continuously present or is present for long periods of time (ia apparatus only)
• Zone 1 Hazardous gas atmosphere is likely to occur during normal operation (ia or ib apparatus only)
• Zone 2 Hazardous gas atmosphere is not likely to occur during normal operatings, or will only occur for short periods of time (ia or ib apparatus only)

Following are typical flammable gases, vapors, and mists. They are classified according to the spark energy required to ignite the most easily ignitable mixture with air.

• Group IIC Acetylene, Hydrogen Group IIA Propane
• Group IIB Ethylene Group I Methane (firedamp)