Analyzer Building, project what I started a some time ago, provides better ventilation system and reduction of classified area from Division 2 Group B to Division 2 Group D. Building is very old with some existing equipment as "general purpose equipment" ( lighting, fans) i.e. with unclassified equipment inside hazardous classified zone.
I have to STAMP this project as P.Eng. but I am refusing.

How does ventilation change the group of the product involved?  The group is based on the physical properties of the product.  In general the code permits non-arc producing equipment that has a normal operating temperature of 80% or less than the ignition temperature of the product involved to be in NEMA 1 enclosures in Class 1 Division 2 areas.The classification change when we ventilate according to NFPA 820 would change area rating from Class 1, Div 1 to Class 1, Div 2 or Class1/Div2 to unclassified (the ventilation rates and monitoring requirements vary with type of space).  Many instruments and analysers are available from various suppliers as rated for installation in classified space (no ventilation required) but this also varies with manufacturer.  Information on type/rate of ventilation and monitoring (NFPA requires status to be monitored to make sure that ventilation is in operation to meet ratings) is required to better understand your situation.

many analyzer building bring in hydrogen for gas chromatographs and the building has lights and heaters not rated for group B. I would have thought forced ventilation, hydrocarbon (calibrated for hydrogen) detector and excess flow check valve on hydrogen line woulkd suffice. Many analyzer buildings have analyzer enclosures with bolts missing. I would think a proactive approch is the best solutio.

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