As the caption says, Joseph Puma (referred to only as Jo in the photo) was a nipper. Nippers, also called trappers or trap boys, opened and closed the doors that sealed off mine shafts so that fresh air could be pumped down to the workers. When the coal cars (usually mule-driven wagons) passed, the nippers had to quickly open the door to let them through, which was dangerous, because there was always a risk of being hit by the fast-moving car. It was a dark, lonely and boring job for long stretches of time while the nipper waited for another car to come, so it was hard to stay awake, making the job even more perilous.

In The Bitter Cry of the Children, a book published in 1909, author John Spargo, a writer and social activist, described child labor conditions in the coal mines in the early 1900s. In the final paragraph, he refers to the plight of the "trap-boys," boys like Joe Puma.

"According to the census of 1900, there were 25,000 boys under sixteen years of age employed in and around the mines and quarries of the United States. In the state of Pennsylvania alone - the state which enslaves more children than any other - there are thousands of little 'breaker boys' employed, many of them not more than nine or ten years old. The law forbids the employment of children under fourteen, and the records of the mines generally show that the law is 'obeyed.' Yet in May, 1905, an investigation by the National Child Labor Committee showed that in one small borough of 7000 population, among the boys employed in breakers, 35 were nine years old, 40 were ten, 45 were eleven, and 45 were twelve - over 150 boys illegally employed in one section of boy labor in one small town! During the anthracite coal strike of 1902, I attended the Labor Day demonstration at Pittston and witnessed the parade of another at Wilkesbarre. In each case there were hundreds of boys marching, all of them wearing their 'working buttons,' testifying to the fact that they were bona fide workers. Scores of them were less than ten years of age, others were eleven or twelve."

"Work in the coal breakers is exceedingly hard and dangerous. Crouched over the chutes, the boys sit hour after hour, picking out the pieces of slate and other refuse from the coal as it rushes past to the washers. From the cramped position they have to assume, most of them become more or less deformed and bent-backed like old men. When a boy has been working for some time and begins to get round- shouldered, his fellows say that, 'He's got his boy to carry round wherever he goes.' The coal is hard, accidents to the hands, such as cut, broken, or crushed fingers, are common among the boys. Sometimes there is a worse accident: a terrified shriek is heard, and a boy is mangled and torn in the machinery, or disappears in the chute to be picked out later smothered and dead. Clouds of dust fill the breakers and are inhaled by the boys, laying the foundations for asthma and miners' consumption. I once stood in a breaker for half an hour and tried to do the work a twelve-year-old boy was doing day after day, for ten hours at a stretch, for sixty cents a day. The gloom of the breaker appalled me. Outside the sun shone brightly, the air was pellucid, and the birds sang in chorus with the trees and the rivers. Within the breaker there was blackness, clouds of deadly dust enfolded everything, the harsh, grinding roar of the machinery and the ceaseless rushing of coal through the chutes filled the ears. I tried to pick out the pieces of slate from the hurrying stream of coal, often missing them; my hands were bruised and cut in a few minutes; I was covered from head to foot with coal dust, and for many hours afterwards I was expectorating some of the small particles of anthracite I had swallowed."

"I could not do that work and live, but there were boys of ten and twelve years of age doing it for fifty and sixty cents a day. Some of them had never been inside of a school; few of them could read a child's primer. True, some of them attended the night schools, but after working ten hours in the breaker the educational results from attending school were practically nil. From the breakers the boys graduate to the mine depths, where they become door tenders, switch-boys, or mule-drivers. Here, far below the surface, work is still more dangerous. At fourteen or fifteen the boys assume the same risks as the men, and are surrounded by the same perils."

"Nor is it in Pennsylvania only that these conditions exist. In the bituminous mines of West Virginia, boys of nine or ten are frequently employed. I met one little fellow ten years old in Mt. Carbon, W. Va., last year, who was employed as a 'trap boy.' Think of what it means to be a trap boy at ten years of age. It means to sit alone in a dark mine passage hour after hour, with no human soul near; to see no living creature except the mules as they pass with their loads, or a rat or two seeking to share one's meal; to stand in water or mud that covers the ankles, chilled to the marrow by the cold draughts that rush in when you open the trap-door for the mules to pass through; to work for fourteen hours - waiting - opening and shutting a door - then waiting again - for sixty cents; to reach the surface when all is wrapped in the mantle of night, and to fall to the earth exhausted and have to be carried away to the nearest 'shack' to be revived before it is possible to walk to the farther shack called home."