Our building inspector said that we need to have a 'ring' around anything
that penetrates the Sheetrock firewall that is between the garage and the
This 'ring' goes around Drain/Vent Pipe, Dryer Duct, Electrical Wires, etc.
and when it gets hot, it expands to collapse the hole. The HVAC guy called
it a medicock ring, though in doing some searching for it I came up with
some, er um, interesting sites.
Can someone point me in the right direction?