09/07/2026
: Digging tunnels for the early was dangerous work. Decompression sickness threatened laborers who worked in compressed air which was used to keep unfinished tunnels from caving in.
Hyperbaric chambers or “hospital locks” were essential emergency equipment, and tunnel workers were required to wear badges bearing the location of the nearest hospital lock in case of decompression sickness. There, they would receive recompression treatment, which would stabilize their condition and relieve symptoms. Because the chambers were expensive and required specially-trained staff to operate, only a few were located around the city.
These images show:
📸 The hospital lock designated for laborers working on the tunnel for the BMT Canarsie Line at 14th Street and Avenue D. 1917, by Granville Pullis.
✍️ Components of a hospital lock, 1915, including carbon dioxide pipe, compressed oxygen pipe, bull's eye window, control valves, gauge, cot, electric heater, thermometer, telephone, and electric lights.
🧷 Badge worn by a tunnel laborer, directing that he be rushed to the specific hospital lock location shown in the first image.