A locked room in the 1750s became a horror story for nearly a century, until science explained what happened … and made every room scary.

In 1758, John Zephaniah Holwell published a dreadful tale of escape and survival. As a British official in India, Holwell was one of the few survivors of “the Black Hole of Calcutta.”

Two years earlier, Siraj ud-Daulah, the new nawab of Bengal, had imprisoned 146 European captives in a small dungeon room for the night. As the heat began to rise in the overcrowded cell, the men fought one another for space near the single, small window and begged the guards for water.

Holwell had a spot near the window, from which he watched as his fellow men, exhausted and overheated, stripped their clothes, lay on the ground, or trampled one another. When the doors opened in the morning, only 23 men emerged. The rest had died in the night.

Holwell’s narrative of thirst and suffocation circulated throughout the British empire and what would become the United States. For many, this horror story exemplified Indian inhumanity and justified British imperialism. But by the 19th century, the story had a new meaning—it illustrated the perils of overcrowded and unventilated rooms.

New York City physician John Griscom retold the story of the Black Hole of Calcutta in 1848 in order to explain new discoveries about respiration and ventilation. Griscom and other ventilation experts explained that the unfortunate men had not died from the heat, but because they ran out of oxygen.

Ventilation experts agreed that a single person required 300 cubic feet of air in order to breathe safely, but Griscom calculated that the dungeon held less than 5,000 cubic feet of air. According to these calculations, the dying men had filled the dungeon with their own exhalations, which Griscom called “carbonic acid gas” but we know today as carbon dioxide.

When the captives inhaled, they filled their lungs not with lifegiving oxygen, but with deadly carbon dioxide. Those who survived also suffered; Griscom explained that survivors had a typhus-like fever that resulted from inhaling foul air laden with both carbonic acid gas and the exhalations of putrefying bodies.

For Griscom, the Black Hole of Calcutta was a cautionary tale about urban life. As New York City grew around him in the 1840s, its buildings became overcrowded and some people moved into windowless cellars. Griscom feared that every crowded tenement and every basement apartment was becoming a black hole.

New Yorkers had built a city of closely packed, poorly ventilated dwellings that sickened them—but Griscom had hope. Since they had built the problem, they could also build the solution. Griscom advocated spending on public parks, which he called “urban lungs” and “breathing spaces” because city residents would go to the parks to breathe. These reservoirs of fresh air would make cities livable and improve the health of urban residents.

Melanie Kiechle, an associate professor in the Department of History, is the author of Smell Detectives: An Olfactory History of Nineteenth-Century Urban America.