Safety lamp could create a sufficient updraft that firedamp would not penetrate down the chimney. Further observations of the speed of flame fronts in fissures and passageways led him to design a lamp with fine tubes admitting the air. Sir Humphry Davy was asked to consider the problems of a safety lamp following the Felling explosion. Previous experimenters had used coal gas (chiefly carbon monoxide) incorrectly, believing it to be the same as firedamp. Davy however performed his experiments with samples of firedamp collected from pits. As an experimental chemist, he was familiar with flames not passing through gauze; his experiments enabled
Safety lamp but cannot pass to the outside. In the Geordie lamp the inlet and exhausts are kept separate. Restrictions in the inlet ensure that only just enough air for combustion passes through the lamp. A tall chimney contains the spent gases above the flame. If the percentage of firedamp starts to rise, less oxygen is available in the air and combustion is diminished or extinguished. Early Geordie lamps had a simple pierced copper cap over the chimney to further restrict the flow and to ensure that the vital spent gas did not escape too quickly. Later designs used gauze for the