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AREA CLASSIFICATION - Hydrogen Ventilation

AREA CLASSIFICATION - Hydrogen Ventilation

AREA CLASSIFICATION - Hydrogen Ventilation

(OP)
Project provides an installation of a small building where HYDROCARBON ANALYZER has to be installed.
Hydrogen has to be used as "fuel" for the HYDROCARBON ANALYZER providing an ionization of the gas samples.
Small vent-chimney is installed on the top of the building.

MY QUESTION :
(1) During summer-time when ouside temperature is higher then inside some problems with Hydrogen Ventilation  can be expected.
IS THERE ANY CHANCE THAT HYDROGEN AS LIGHT GAS CAN BE CONCENTRATED INSIDE A BUILDING BECAUSE OF WARM AIR OUTSIDE OF THE BUILDING. CAN THAT WORM AIR ( heavier than hydrogen)
CLOSE THAT CHIMNEY MINIMIZING A NATURAL VENTILATION OF THE HYDROGEN.

RE: AREA CLASSIFICATION - Hydrogen Ventilation

Draft is generated by cooler heavier external air pushing the lighter (warmer) gases up to the chimney and out. For that to happen an air intake should be available: an open window or door or some kind of ventilating/breathing openings, grating, vanes, etc.

An inverse draft situation could indeed be originated by a density reversal. A small fan could be used to ensure that the generated gases are always expelled from the analyzer housing through the chimney.



RE: AREA CLASSIFICATION - Hydrogen Ventilation

The use of hydrogen in the buildings might  imply all cieling and roof fans be explosion proof.

The density difference between H2 ( mw=2 ) vs air ( MW=29) would imply the outside air would need to be about 14.5 times greater than the hydrogen to cause a reverse draft. Indoor air at 60 F ( 520 R) and outside air at 7540 R is a mighty warm day.

RE: AREA CLASSIFICATION - Hydrogen Ventilation

bobziva, With any type of flammable gas in an enclosed space, forced ventilation of the area needs to be used at all times. I wouldn't depend on natural ventilation to do the job.


Hope this helps.
saxon

RE: AREA CLASSIFICATION - Hydrogen Ventilation

Assume you are talking about a chromograph type hydrocarbon analyzer.  If so, the hydrogen bottles usually have a heater and gas blanket on them.  The bottles are also located in a separate room from the analyzer.

Also, analyzer buildings are generally air conditioned.

My electrical friends also say that the analyzer room is classified as non-hazardous by the NEC.  For additional information on area classifications see API 500.

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