Q1.1
(a) Firstly, the knowledge of hazardous area should be known which can be defined as an area which contains or may contain some amount of dust or vapors or sufficiently danger causing flammable or explosive gases; normally areas like oil rigs, petrol stations etc. Secondly, the knowledge to classify it by IEC or ATEX standards i.e. the type of hazard, the temperature at which the hazardous material in the area auto-ignites and the flammable concentration.
In the American and Canadian classification system (of hazardous areas), they refer to a CLASS I, CLASS II and CLASS III. Please explain the difference between them.
(b)
The three classes of hazardous areas can be differentiated on the basis of nature of contamination present in that particular area. Class I contain all those areas which are polluted by gases or vapors which ultimately make the environment combustible. Class II includes those areas which contain explosive dust and Class III includes those areas which contain combustible fibers (not in the air but on floor).

Q1.2
(b)
Compressed gases can be toxic or very toxic which readily means that they could cause health problems depending on the gas exposed, the concentration of toxic gas, length of exposure to the workers and the way of exposure ,eyes skin or during breathing. Contact between the skin or eye and liquefied gases in liquid form can freeze the tissue and result in a burn-like injury.

Q1.3
(a)
IEC defined Group IIA deals with the atmospheres containing propane, or gases and vapors of equivalent hazard. While Americans or Canadians defined Class I deals with Acetylene. It can be seen that Group IIA is more dangerous because of higher tendency to react with oxygen.

(b)
GROUP IIC deals with acetylene

The following data was obtained at failure in conjunction with a un...