Children as young as 8 years old worked in dangerous conditions during the Industrial Revolution to meet the high demand for coal. They worked long hours in dark, cramped mines where the air was thick with coal dust, sorting coal from rock and risking injury from cave-ins. Those who worked as "breaker boys" faced numb fingers from the cold and pressure from overseers to work faster. Many children suffered injuries or lost fingers in the machinery in the mills and factories where they replaced bobbins or pushed coal carts through narrow tunnels.