On December 2nd, 1848, 150 years ago today, the paddle steamer Londonderry ran for shelter towards the northern port from which it took its name.
It had left Sligo, bound for Liverpool, with a large complement of emigrants accommodated in the hold. As it passed the coast of Donegal a violent storm blew up. The grills on deck that acted as ventilators for the hold were blown away and, to prevent water from entering, the crew covered the openings with tarpaulin.
A grisly spectacle awaited those who removed the covers in the shelter of Lough Foyle. It was found that 72 men, women and children in the hold had suffocated.
They where buried together in a mass grave near Derry's workhouse, a grim illustration of the effect on humans of the lack of proper ventilation.
Four major changes can be identified as taking place in the air of a confined space as a result of human occupancy.
Two of these are obvious: by their collective breathing, the crowd reduces the oxygen content of the air, and increases the proportion of carbon dioxide. In addition, body heat from the assembled humans increases the temperature of the environment, and the moisture of their exhalations brings about a rise in humidity. It is common experience that this may cause discomfort, but as we have seen, the combination, taken to extremes, may well be lethal.
The classic example of such a tragic incident is the callous act so infamously remembered as the incarceration in the Black Hole of Calcutta.
It happened on June 20th, 1756, when one Sarij-Uddaula was Nawab of Bengal in north-east India. According to a contemporary account: "On one of the hottest nights in British India, Sarij-Uddaula caused to be confined within a small cell at Fort William, 146 Englishmen whom he had that day captured in a siege of the city of Calcutta. The room was large enough to house comfortably but two persons. Its heavy door was bolted; its walls were pierced by two windows barred with iron through which little air could enter.
"Within a few minutes after entrance every man was bathed in a wet perspiration and was searching for ways of escape from the stifling heat. As the steaming mass of sentient human bodies vied for the insufficient air, clothing was stripped off, breathing became difficult, and there were vain onslaughts on the windows and attempts to force the door. The night passed slowly but, with the advent of morning, death had come to all but a score of the luckless company in that airless dungeon in Calcutta."