AREA CLASSIFICATION - Hydrogen Ventilation

[bobziva]

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.

 

[25362]

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.

 

[davefitz]

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.

 

[saxon]

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

 

[1969grad]

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.