I have read at http://www.zomeworks.com/tech/H2/H2vent.html described
under 'The Diffusion H2 Vent' that high density fibreboard will vent
H2 from an enclosure by gravity while blocking airflow.  I want to
test the ability of fibreboard to
pass H2 and design my own indoor battery enclosure.  It is important to
block air flow to maintain the thermal mass of the battery.  I want to
use my enclosure indoors and use fibreboard (or some other cheap
material) as an 'open gravity vent' for the H2.  The battery box will
be in a room which has a second fibreboard gravity vent in the ceiling
to outside or upstairs where the concentration of H2 is not an issue.

1. What kind of test setup and measurement procedures/equipment would
be appropriate (and reasonably cheap) to evaluate the permeability of
fibreboard for H2.  I am interested in precision only to the extent
necessary to determine how close I am to an explosive H2/air mixture
at normal room temperature.

2. I expect to generate about 4 cubic feet per hour of H2 during the
final phases of battery charge.  The objective is to prevent an
explosive mixture from being created in the battery box during the
last 20% of battery charge when H2 is created.  If the free
space within the battery enclosure is 1 cubic foot, how would I size
the fibreboard vent to dissapate H2 by gravity out the top of the
enclosure without help from a pump?

3. What physics/chemistry principles are relevant?  I plan on using
some of the calculations at
http://www.bhs1.com/batteryroom/ventilation.htm as a sanity check on
my tests.

4. Are there other low cost materials that might be as permeable to H2
while blocking air and how would I find them?

5. Are there internet sites who experiment and discuss detecting or
venting H2?  I see http://www.h2scan.com/technology.html has a product
to detect H2 but I am afraid to ask the price.