Sensors and switches used to monitor machinery must be approved for use in the location in which the machine they are monitoring resides.  These locations are divided into 4 types.  The First of these is a standard location meaning there is a normal atmosphere without danger of explosion.  The second location type, called Class I, is where explosive gases exist.  The third location type, called Class II, is where combustible dusts are present.  The fourth location type, called Class III is where combustible fibers or flyings may be present.  Sensors and switches used in these hazardous locations require testing and certification by a Nationally Recognized Test Laboratory.  Several methods of protection may be used in the construction of the sensor or switch, these methods include Explosion-Proof or Dust Ignition-Proof enclosures, or Intrinsically Safe Design.  

Explosion-proof enclosures can safely contain and then vent an explosion inside the enclosure, this method is for use in Class I locations.  

Dust ignition-proof enclosures prevent dust from entering the enclosure and maintain a cool surface temperature when covered in dust, this method is for use in Class II locations.  

Sensors designed to be Intrinsically Safe use very little power so that there is not enough energy present in the circuitry to ignite the explosive atmosphere in the event the sensor or wiring is damaged.  

For more information on Hazardous Environmnents please visit the National Fire Protection Agency.

Please contact Electro-Sensors, Inc. for assistance in choosing the best sensor or switch for your application with regards to performance and the type of location it will be used in.