Canaries in Coal Mines

Sometime between 7:00 and 7:30AM the morning of November 6, 1922, a stray spark ignited a pocket of gas deep beneath the town of Spangler, Pennsylvania. Several men working inside the Reilly coal mine were immediately killed by the blast, thrown against the cave wall by the force of the explosion that also caved in the ceiling and destroyed the mine’s ventilation fan. Within seconds, a fireball ripped through the mile-long shaft that connected the mine’s depths to the surface, ravenously consuming all of the oxygen along the way. In its wake, the conflagration left behind a noxious mix of smoke, carbon dioxide, methane, hydrogen sulfide, nitrogen, and carbon monoxide, a lethal mixture that miners called afterdamp. There were one hundred and twelve miners trapped in the suffocating darkness who would die if they did not reach fresh air quickly. 

A crowd of five hundred rescuers rushed to the mine to begin clearing a pathway to their brothers, fathers, friends and neighbors, but the gasses often proved too much for them. They managed to return with five miners on the brink of death before they too had to retreat to the surface. Many of the rescuers were hospitalized from the effects of breathing poisoned air. It was only when a professional crew of emergency rescuers arrived with their oxygen tanks that the party could reach the miners trapped deeper in the earth.

The smallest member of this elite rescue party was named Sally. Sally had a storied career, having completed more than a dozen missions, even though in most of them she needed to be carried out of the mines after being overcome by carbon monoxide gas.

You see, Sally was a canary, and she had one simple but vitally important job. She just had to keep breathing.  Sally took more than sixty breaths every minute, cycling through twenty times as much oxygen as humans relative to her body size. As she needed so much air, she was also much more sensitive to its purity. If the air contained a concentration of 0.25% carbon monoxide, it would take just ninety seconds for Sally to start swaying on her perch. In five minutes, she would be unconscious on the floor of her cage. 

The human rescuers, in contrast, could breathe in the colorless, odorless gas for twenty minutes before starting to notice a headache. Twenty more minutes of exposure could be fatal.

As the rescuers plunged deeper into the mine, they noticed Sally start to rock unsteadily on her perch. She was beginning to feel the effects of carbon monoxide. Though they couldn’t notice its effects yet, the rescuers now knew that they too were breathing poisoned air. They slipped on their masks and began drawing on their precious supply of bottled oxygen, which would only last two hours until they themselves would need saving. 

At this point, someone would normally turn back to bring Sally to the surface and to fresh air. She’d had this brush with death a dozen times before, and each time had made a full recovery. But as soon as she fell from her perch, one of the rescuers spotted some writing scrawled on a plank, left by one of the survivors trapped in the mine’s labyrinth: “There are 29 men behind this.” The crew knew they faced a choice between Sally’s life and the lives of the miners.

In the days following the disaster, one of the rescuers reflected on the decision to all press forward. “It was a shame,” he said. “We could have saved her if we had retreated to the good air. But where the lives of miners are concerned, I guess Sally would O. K. our act in going ahead.”¹

Over the next twelve hours, rescuers led or carried thirty survivors out of the mine’s depths, all of whom suffered from severe carbon monoxide poisoning. But eighty men — most were no older than twenty-one — did not make it out alive. Almost all of the victims were killed by poisoned air.²

Sally was buried alongside the fallen miners, and granted honors that fit her status as a rescuer that sacrificed her life to save another. She was wrapped in a tiny American flag, placed in a coffin, and buried under a small white cross that read “Here lies Sally, a good canary, who gave her life to save the lives of professional and volunteer rescuers in the Reilly mine disaster, November 6, 1922.”³

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British scientists in the 1890s were the first to land on the idea that animals might provide an early warning to miners that the air was unsafe. A petting zoo worth of small creatures was auditioned for the role of sentient carbon monoxide detector, and canaries were found to show symptoms most quickly, followed by mice, chickens, small dogs, pigeons, English sparrows, guinea pigs, and rabbits. What’s more, canaries showed obvious signs of poisoning by swaying and falling from their perches, whereas mammals mostly just got drowsy.⁴

Rescue canaries were first put to the test in the United States following an explosion in a Briceville, Tennessee mine in 1912. Men wearing oxygen masks and carrying caged canaries walked ahead of the larger rescue party. At the point that the canary’s body began drooping, the crew knew that only those with an oxygen tank could continue further. The experiment was deemed a success.

It didn’t take long for canaries to be added into America’s official mine rescue protocol. The U.S. Bureau of Mines kept rescue cars in each of the country’s large mining districts, ready to be dispatched as soon as word of a disaster arrived. Each car was stocked with lamps, stretchers, oxygen tanks, helmets, and axes, and it soon became government policy to add a half-dozen canaries, which were “cared for tenderly by the men continuously on duty in the car.”⁵ A 1923 Bureau report explained that “a canary in a small portable cage is an almost indispensable adjunct to rescue work after a mine explosion or during a mine fire.”⁶

But to the rescuers, these birds were never just lines on an equipment manifest. They were less like pets, and more like brothers in arms to whom the rescuers frequently owed their lives. The rescuers repaid this debt by making every effort to protect the birds they carried at their side. Once canaries showed signs of sickness, they were quickly carried to the surface. “If handled intelligently,” wrote a reporter covering the Reilly Mine disaster, “they seldom die as a result of exposure to atmospheres containing this deadly gas. It is only in rare cases such as Sally’s that the bird-sacrifice must be made for the sake of humanity.”⁷ Engineers eventually developed a special cage that could be sealed off and pumped full of oxygen whenever a bird began drooping, which all but ensured the bird’s survival.

The era’s animal rights activists, who vigorously criticized caging other birds, also recognized the necessity of using canaries to save human lives despite their sympathy for the birds’ plight. “To see them go down on what is at present a necessary mission of mercy is pathetic,” wrote one, “for the dark and gloomy pits are the very antithesis of the natural haunts of the joyous sun-loving ‘children of the air.’”⁸ Still, they wondered why a mechanical replacement hadn’t yet been developed to relieve canaries of their sometimes-fatal service. 

Fortunately, the defenders of animals did not have long to wait. In the mid-1920s, engineers developed a mechanical carbon monoxide detector that improved on the canary’s biology. These portable machines were much more sensitive, gave results more quickly, and provided continuous readings of the amounts of gas present. With the new device’s widespread adoption, one mining trade periodical reported that “the field of usefulness of the canary [has been] greatly restricted.”⁹ By 1930, canaries in coal mines were a thing of the past, at least in the United States.

But in the United Kingdom, canaries stayed on the job for another seventy years. An act of parliament from 1911 required that every rescue station keep a canary, and no one changed this law after carbon monoxide detectors were developed. Decade after decade, British canaries continued their life-saving labor long after their American cousins had been turned out to pasture. Not until 1996 did parliament fully modernize their requirements for rescue stations, and the last generation of canaries was sent to live out their remaining years as devoted pets in the homes of their former colleagues.

“First to fall over when the atmosphere is less than perfect,

Your sensibilities are shaken by the slightest defect.”

The Police, “Canary In A Coalmine,” 1980.

Since the last English rescue canary was retired in 1996, any canaries in coal mines have been entirely metaphorical (well, almost entirely. In 2001, the birds briefly surged to popularity in New York City following fears of a hypothetical chemical weapon attack. One Petco employee said “I don’t want to seem unpatriotic or anything, but canary business has been great ever since September 11”).¹⁰ But this obscure lifesaving technique for mining disasters has still managed to lodge itself permanently in our colloquial English. 

Google Ngram is a fascinating tool that illustrates the relative popularity of a word or phrase over time by measuring its frequency in the immense Google Books library. Searching Ngram for “canary in the coal mine” shows that the phrase wasn’t used while canaries served in American mines. It only rocketed to popularity in the 1980s, toward the end of the working canary’s tenure in the UK. 

In the 1980s, the United Kingdom was the scene of vigorous and sometimes violent clashes between activists and the state over nuclear weapons, labor, and the environment. In 1983, more than three hundred thousand protesters gathered in London’s Hyde Park to push for nuclear disarmament. The following year, in response to Margaret Thatcher’s decision to close most of the country’s coal mines, the National Union of Mineworkers launched a strike that lasted twelve months, claimed three lives, and became one of the largest and most bitter strikes in Great Britain’s history. 

I haven’t been able to find anything that conclusively ties the emergence of the phrase to Thatcher’s tumultuous decade. But I’m convinced that the aphorism came from the UK, where canaries in coal mines weren’t an obscure and distant memory of an industrial safety protocol, but the lived reality of miners struggling to keep their jobs and their heads above water, a reality that resonated with every parent and child concerned about a future threatened by environmental disaster and nuclear war.

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Five years ago, a report in the journal Science revealed the alarming finding that three billion birds had disappeared from North America since 1970, nearly a third of the continent’s total. Warning that their disappearance should concern everyone, not just birdwatchers, John Fitzpatrick and Peter Marra explained that “birds are indicator species, serving as acutely sensitive barometers of environmental health, and their mass declines signal that the earth’s biological systems are in trouble.” 

It hasn’t taken long for us to come full circle. Birds are our canaries, and we’re living in the coal mine.

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1. “‘Sally,’ Mine Disaster Heroine.” Gas Logic, Vol. 33 no. 1. January, 1923. ↩︎
2. Kelly, Hayden. “Spangler Mine Explosion.” The Philadelphia Inquirer, Wednesday, November 8, 1922. ↩︎
3. “‘Sally,’ Mine Disaster Heroine.” Gas Logic, Vol. 33 no. 1. January, 1923. ↩︎
4. Forbes, John Joseph Vincent., Grove, George Wallace., McElroy, George Edward. Mine Gases and Methods for Detecting Them. United States: United States, Department of the Interior, Bureau of Mines, 1954. ↩︎
5. “‘Sally,’ Mine Disaster Heroine.” Gas Logic, Vol. 33 no. 1. January, 1923. ↩︎
6. “Mine Rescue Standards: A Tentative Study.” US Department of the Interior Bureau of Mines. United States: U.S. Government Printing Office, 1923. ↩︎
7. “‘Sally,’ Mine Disaster Heroine.” Gas Logic, Vol. 33 no. 1. January, 1923. ↩︎
8. “Bird Life Savers out of Work.” Dundee Courier, 19 Oct. 1926, p. 6. British Library Newspapers. Referenced in Bonney, Amelie. “Canaries in the Coal Mine.” The Gale Review, September 8, 2020. ↩︎
9. Parker, D. J. “Status of Mine Rescue Work – Equipment and Personnel.” Coal Mining. United States: n.p., 1927. ↩︎
10. Wapshott, Nicholas. “Why Canaries Are Flying Off Their Perch.” The Times (London, England). Friday, November 2, 2001. ↩︎