It is tempting to remove them, but chimneys should not be reduced in height as this can result in downdraughts, causing smoke to blow back into the room.
Mae'n demtasiwn eu symud, ond ni ddylid lleihau uchder simneiau am y gall hyn arwain at ddrafft i lawr, gan achosi i fwg chwythu'n ôl i mewn i'r ystafell.