Ex設備，即指防爆電氣設備，是指使用在危險場所的電氣設備。而所謂危險場所，是指空氣中因含有一定量的易燃性的氣體（蒸汽、液體、粉塵）而有可能引起著火和爆炸危險的場所。
對於危險場所的定義可參考IECEx的官方解釋：
What is an Ex area?
Ex areas can be known by different names such as “Hazardous Locations”, “Hazardous Areas” “Explosive Atmospheres”, and the like and relate to areas where flammable liquids, vapours, gases or combustible dusts are likely to occur in quantities sufficient to cause a fire or explosion.
The modern day automation of industry has meant an increased need to use equipment in Ex areas. Such equipment is termed “Ex equipment”
http://www.iecex.com/about.htm
