Over the years, others changed Davey's early lamp. One "improved" model, which produced a brighter light, substituted gasoline for oil. However, many engineers considered that model more dangerous because the gasoline lamps tended to get hotter, especially where the air was gassy, and its glass cylinders broke more frequently than those on oil lamps. To offset the problems, designers increased both the size of the lamp and its weight. They also substituted thinner glass in the cylinders because thinner glass was less likely to break from uneven expansion than the heavier glass; however, the thinner glass broke more often when a miner dropped his lamp and could trigger an explosion. Another danger of the gasoline model was that the flame went out more frequently, thus requiring a miner to relight it -- again risking an explosion.