Look at things this way.
you go into your house and smell a gas leak. at that point you should leave your house immediately with the door open and call the gas company. No problem.
what you do not need to do is create a spark which can ignite the gas vapors in the room, and cause an explosion.
you can obviously create a spark by striking a match, using a lighter.
you can also create a spark by unplugging / plugging in an electrical device, turning on a light switch, or other similar things. the manufacture of devices like that ASSUME that there is nothing in the area that will explode or catch fire. they are not made to keep out dangerous gases and the things I discuss below. That's why they place the warning. you need to know the area where the device is to be used.
the manufacturer is stating that there might be enough potential energy when you flip the switch or unplug / plug in the device to create a spark. that spark may have energy in it to cause gas vapors, dusts, of fibers to ignite and create a fire or explosion.
Hazardous locations are defined by a class and division.
Class 1 - flammable gas, vapors, or liquids.
Class 2 - combustible dust.
Class 3 - ignitable fibers or flyings
Classes are also defined into divisions.
Division 1 - The area has material in the environment at all times during the manufacturing process and for a period after manufacturing has stopped. some areas never stop having the materials present.
Division 2 - the area has the potential for an explosion during an abnormal situation or in an emergency.
I have worked in class 1, div 1 and 2, Class 2, div 1 and 2 for 12 years.
creating a spark in these areas is very serious.
We had devices that would detect a spark 1/4 mile away. NO JOKE. our deluge system would flood the area within 23ms when a spark was detected with 110 gallons per minute per nozzle.
in these areas, you would need intrinsically safe barriers to prevent such a spark.
I hope this explaination helps,
james
