The heat transfer using Steve's suggestion is conduction i.e. direct contact (iron to jeans to carpet to glue). If you were trying to transfer enough heat to melt the glue just by heating the air you would have to crank up the iron hotter than hell to heat the air (a very poor conductor of heat) which would result in a huge amount of radiant heat transfered to the carpet. And you're telling me that it wouldn't damage the carpet. Maybe wool carpet, but who installs that anymore?