Fire
If human skin touches fire, the skin may burn, which can take some time to heal and to remove the scar.  If a fire gives off a large amount of smoke, a person's mouth should be covered with a wet cloth, since people can faint when they breathe in too much smoke.  Even a spark, such as from a cigarette, should be kept away from any fuels that very easily catch and spread fire, like gasoline, or cause an explosion, like gunpowder.