On 19 Feb 2007 06:54:51 -0800, "theCase" wrote:

Why do gas water heaters require external venting while gas stoves do
not? Is there something fundamentally different in the combustions
byproducts (CO vs. CO2) that need to be vented for the water heater
and not the stove?

If the only reason is the volume (BTU rating) of byproducts, it
doesn't make sense. For example, a moderate water heater can have a
rating of 75,000 BTU, while a high end stove will have a total BTU
rating over 100,000.

Worse case, think about cooking a Thanksgiving meal, oven is on for
six hours and all the burners are going, all this is vented inside the
house. While downstairs the water heater just has a pilot light
going. Why is one required to have external venting while the other
one doesn't?

Actually a 4 burner plus over gas range creates very little CO when
it's burning correctly. Also, as another poster mentioned, the stove
can be observed wihile a semi hidden gas water heater can not.

I've run my unvented gas oven consistently and have a CO detector in
the kitchen. My detector is one of those Nighhawk types that with a
push button, can give low level reading below the alarm threshold.
Rarely do I see even any trace CO from the range.

Occasionally during summer days, I've seen trace amounts of CO on the
detector that come from outside air. The ambient air due to distant
auto exhaust probably has more CO than a properly operating gas range.

I've never thought that range hood venting was even designed for CO
elimination. They are more often designed for odor and smoke
elimination. Many such range hoods are not even vented to the outside.
They are vented within the home after having the gases pass thru
multistage filters.

BTW, the standard gas water heater has a burner BTU rating of 35,000
BTU/hr, that's nowhere near 75K/hr. The only gas water heaters that
I've seen with 75K or higher rated burners were commercial units used
in apartment buildings.

Doug