Hello Allen & All,
The bleach sold in the U.S. is also 5.25% Sodium Hypochorite.  I never
thought about the killing being possibly done by the release of chlorine
gas.  If you are correct then you are right the spores are killed by
fumigation.  If you are not then they are in fact killed by contact which is
my interpertation of the test results.
Each hive infected with AFB is different.  I have watched inspectors burn
equipment which I thought could have been salvaged by scorching and then
only recommend Terramycin for others I though should have been burned.  Most
foulbrood is found in brood  frames.  It is my opinion that most of the
chances of AFB comes from the area of frames.   I have always  burned
complete hives or scorched hive parts just to be safe.   Most foulbrood is
confined to the infected hive in the early stages.  Once the hive has been
heavily infected died and has been robbed out all hives in flying distance
are at risk.   If the hive belongs to a hobby beekeeper which has lost
interest, bees will return to the deadout and bring spores back for many
years.  Bees seem facinated with going in old dead hives and looking around.
I have found several old apiaries full of old deadouts with AFB.  I have had
to myself destroy many of these hives.  Even had trouble with the owners
over the destruction of the worthless hives and had to call the state
inspector to get the hives taken care of.   Are some of our AFB problems
comming from old not taken careof deadouts full of AFB spores being robbed
out by our bees. We all know that there are hundreds if not thousands of
varroa killed deadouts sitting in backyards across the U.S. and other
countries.
Bob