HAC

By considering types and sizes of potential releases, of course. If in doubt, consult a qualified Chemical Engineer locally.

• If a Zone 1 is large, the plant has a serious materials containment problem that must be addressed as a very high priority. Most jurisdictions will prosecute if an operator is to be placed in Zone 1, on the threat to personal health and safety grounds.

Blimey! That's the leakiest plant in the world, Mildred!

Nah, that is common. Think less "where the gas is" in normal plant operation and more where "where the gas theoretically could be" in the event of an abnormal leak or for very short periods.

Ah, so the caution is 'ratcheted up' to 'If, on a bad day, the gas level could exceed half a beer-fart, then don't even THINK of lighting a match in the area.'

Yeah, it may seem paranoid, but all safety systems seem paranoid, until the first time someone DIES from violating/bypassing them. As the old saying goes, "The are Old Electricians and there are Bold Electricians, but there are no Old Bold Electricians." I think we'd all prefer to be here as cranky old guys/gals than to be 'remembered fondly' for 'being taken too soon' due to our own 'brave actions' to 'improve productivity at the plant.' If I'm not gong to live long enough that EVERYONE forgets how old I am, I'd rather pass on from natural causes instead of giving up my life to try and improve someone else's profit/loss sheet.

Ah, so the caution is 'ratcheted up' to 'If, on a bad day, the gas level could exceed half a beer-fart, then don't even THINK of lighting a match in the area.'

Yes but when referencing the IECEx standards we prefer to say "classified as a Zone 2 area" instead, sounds more professional.

Yeah, it may seem paranoid, but all safety systems seem paranoid

Unlike your average safety systems accidents, accidents in hazardous areas tend to effect more than one person losing a finger (for example).

Savety: It's all fun and games until someone has to explain to little Sally that Daddy isn't coming home again, ever.

If the shoe fits, you may wear it (after you buy it):

API RP 500 Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division I and Division 2, Third Edition

Available from www.techstreet.com

Do you have a copy of IEC 60079.10.1 - Classification of areas - Explosive gas atmospheres? If not buy one as this is the document you should be using for zone planning to IEC standards.

Zone radius selection is explained including application specific examples and selection formulas. If the standard is not clear enough or your not qualified to perform this work you will have to hire a consultant to do it.

Firstly my apologise for replying late.

Thanks all of you providing me good useful informations.