[Joralemon Street Tunnel: IRT Lexington Avenue Line]

Photograph of a sandhog exiting the 'man-lock' between Furman and Joralemon Streets, Brooklyn during the construction of the IRT Lexington Avenue Line. A 'man-lock' is a pressurized chamber. One of the occupational hazards of tunnel work was a condition known as 'the bends,' caused by a build-up of gas bubbles in tissue. The highest pressure in a tunnel was 100 pounds per square inch. Men could work under these conditions only for half hour shifts.