Hazardous Classification How to tell

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gadfly56 said:
You clearly have no experience in an MEP firm. There is certainly no cause for such gratuitous insults. My colleague is an EIT, but he's every bit an engineer. Until recently all work out of all our offices had to be signed and sealed by our principal. I can assure you his review was quite thorough.
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Sorry dont take every situation personally. My experience as reviewer has met many PEs, principles, MEP firm and is my experience. AHJ infact writes letter to stop electrical drawings stamp from MEP firm principles PE who send trash drawings design done by others to state board who take action against PE to stop producing trash. Reparmand, suspension, revoke you name it. My situation may not apply to yours. Its my experience and which is why I like EIT.

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jumper said:
Engineers of course, if they have BSEEs, but there is a slight presumption that when someone says they are an EE here, it kinda implies being a PE in electrical IMO.

Or at least that is what I infer. Bad assumption on my part I suppose.
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Hmmmm, well we all have our preconceptions. For myself, I don't automatically assume an engineer is a PE. Half aren't, after all. The NCEES says there are 820,000 PE's in the US. I don't know if that's corrected for those who hold multiple licences. The BOL says there are 1.6 million engineers, excluding computer occupations.
 
codequestion said:
Anyways it is at best class 1 div 2. It would have been class 1 div 1 if it werent for fire cabinet protection.

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So the fire cabinet is keeping the items out of it, safe? I thought they were cleaning stuff with the items from the cabinet, in some lab hood type thing?


I should have went to college for learning instead of drinking college kids beer while i was home from work... This whole conversation might have made some sense.

Side Question
500.5 (B) 2 (2) says something about positive pressure from a vent. Does this mean that it is adding oxygen (positive pressure) to a area instead of removing it? Also does it have to have a shut off for fires and such? Adding oxygen to a fire would be bad in my mind. Unless they are talking cabinets (which makes since there, keep gases out of it) wouldn't they want the fumes removed from the area/room to limit the amount hazardous fumes/gases?
 
AKElectrician said:
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Side Question
500.5 (B) 2 (2) says something about positive pressure from a vent. Does this mean that it is adding oxygen (positive pressure) to a area instead of removing it? Also does it have to have a shut off for fires and such? Adding oxygen to a fire would be bad in my mind. Unless they are talking cabinets (which makes since there, keep gases out of it) wouldn't they want the fumes removed from the area/room to limit the amount hazardous fumes/gases?
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It seems to me that it is saying that an area adjacent to a Class I Division 1 area which would otherwise be classified as Division 2 can instead under some circumstances be unclassified if it is kept at a positive pressure with respect to the Div 1 area.
One way of doing this is to supply air under pressure through a vent from a source of clean air which is not itself Class 2 or subject to direct contamination from a Division 1 area.

PS: Increasing the pressure by the amount generally considered to be positive pressure in the ventilation context will not noticeably change the oxygen concentration.
The concern with shutting off forced incoming air when a fire is detected (e.g. in kitchens) has to do with supplying fresh air (including oxygen) to an existing fire. The concern in the case of classified areas is very different.
 
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GoldDigger said:
It seems to me that it is saying that an area adjacent to a Class I Division 1 area which would otherwise be classified as Division 2 can instead under some circumstances be unclassified if it is kept at a positive pressure with respect to the Div 1 area.
One way of doing this is to supply air under pressure through a vent from a source of clean air which is not itself Class 2 or subject to direct contamination from a Division 1 area.

PS: Increasing the pressure by the amount generally considered to be positive pressure in the ventilation context will not noticeably change the oxygen concentration.
The concern with shutting off forced incoming air when a fire is detected (e.g. in kitchens) has to do with supplying fresh air (including oxygen) to an existing fire. The concern in the case of classified areas is very different.
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I am not mechanical engineer but dont hoods take air away and add negative pressure?

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codequestion said:
I am not mechanical engineer but dont hoods take air away and add negative pressure?

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Yes they do. And as a result they produce a positive pressure (relative to the possible Div 1 area inside the hood) outside the hood.
Not directly what the referenced code section is talking about, but the same principle underlies it.
 
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