I have seen hearth gates (pretty $$$ though) that are designed to box in your stove/fireplace area while allowing the adults access. They hard mount into the wall on either side. There are other gates that look like they can do the same thing, but I'm not sure if the hearth gate has a special finish or anything for the heat that would justify its cost over that of a more ordinary gate. The links below are just examples, I'd look around for the best prices and some other styles.
http://www.onestepahead.com/catalog/...tegoryId=85217
http://www.onestepahead.com/catalog/...tegoryId=85217
http://www.onestepahead.com/catalog/...tegoryId=85217
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Karen