[Note that this article is a transcript of the video embedded above.]

Excitement and hope permeated the crowds gathered in a dusty farm carved from the piney woods in east Texas. The rumor was that Columbus Joiner had struck oil. At 70 years old, Joiner had already won and lost several fortunes in the oil business, but it seemed like, on that October afternoon in 1930, he might just have one more in him. As the congregation grew, Joiner and his crew slowly swabbed the water and mud up and out of the well, relieving the pressure at the bottom. Eventually, the ramshackle derrick began to rumble and shake. Suddenly, the Daisy Bradford No. 3 erupted, showering black oil on the cheering crowd. It was the “discovery” well for what would quickly become the largest and most prolific oil field in the continental United States at the time. Joiner would lose that fortune too, but the boom he kicked off would change the state forever.

The sudden inrush of oil workers and their families inundated the area, including the unincorporated town of New London. New families needed a new school, so one was built in 1932. But no one could have imagined that what created the town in the first place would ultimately rob it of a generation only a few years later in one of the worst school disasters in US history. I’m Grady, and this is Practical Engineering.

With all of the extra population and tax revenue pouring in, New London quickly became one of the wealthiest rural school districts in America, and its new school was correspondingly designed. The building sat on a gentle slope with a footprint shaped like a large capital letter E. Both the north and south wings projected out from the hillside, creating space for classrooms below the main floor. But the main part of the school had a mostly unused crawlspace below its first level. This crawlspace had just two doors into the basement wings and four small vents to the outside for circulation. The school was originally designed to be heated by a large central boiler, but the school board changed the plan during construction to install cheaper, individual gas-fired radiators throughout the building. Gas was supplied by a local utility company for the following years until an opportunity arose in January 1937.

The Parade Gasoline Company had constructed a condensate extraction plant not far from the school. Natural gas is an incredibly important resource today, but at the time, it was mostly considered a byproduct of oil drilling. The supply was just so much higher than the demand because gas was difficult to transport at large scales. Networks of long-distance natural gas pipelines wouldn’t arrive until after World War II. But it was possible to extract liquids from raw natural gas by cooling the vapor. The resulting condensate (often known as “drip gas”) had many uses and could even be used as a low-quality substitute for gasoline in older engines.

Parade’s plant was a simple operation. It accepted raw natural gas from nearby wells, extracted the condensates, and then sent the “residue” gas back to the oil fields in another pipeline, where it was mostly burned off in flares. Since it was already a kind of garbage gas, it was common practice at the time for homes, businesses, and public institutions within easy reach of the residue pipe to tap a line without explicit permission to get the free gas. Since the company was already getting rid of it, they were usually happy to look the other way.

This might seem like an outrageous and dangerous practice today, but it’s not hard to become accustomed to risk, especially when lots of people are doing the same thing and the benefit is so immediate and obvious. In New London, the school board saw an easy opportunity to save about $250 per month on their heating bill (several thousand dollars in today’s money). In January of 1937, the connection was made by two bus drivers, a janitor, and a local welder. A radiator salesman inspected the new line. They installed a regulator to reduce the sometimes erratic pressure from the residue pipe. From there, the gas would flow into the school building’s crawlspace along a 2-inch line suspended by straps. 96 individual connections tied the main gas line to the heaters and burners throughout the school. But the district would never get to see the savings of the supply switch.

On Thursday, March 18, 1937, near the end of the day, the school was full of students and teachers eager to be let out for a long weekend. In the basement wood shop, near the crawlspace, a teacher powered on an electric sander, flipping a rudimentary knife switch to complete the circuit. Unbeknownst to the shop teacher and everybody else in the building, the crawlspace had filled with an explosive mixture of residue gas and air. The spark from the knife switch was all it took to ignite the gas and set off a terrible explosion.

Except for the two doors and four small vents, the crawlspace was practically a sealed chamber of concrete. With nowhere to escape, the pressure of combustion lifted the first floor of the building upward, buckling the walls, and then collapsing the roof into the school. A large chunk of a concrete slab was blown over 200 feet from the building, crushing a car in the nearby parking lot. There were over 500 students, faculty and staff in the building at the time. Chaos ensued as many parents, who had been at the PTA meeting at an adjacent building, reacted to the thunderous sound and ran to the scene. Soon, the school was overwhelmed by residents, oil field workers, and emergency personnel, all doing whatever they could to rescue victims within the collapsed building.

The Texas Inspection Bureau report described the effort involved:

The removal of this debris is worthy of comment since it is probable that in no past disaster of record, has it been approached in speed or efficiency and nowhere but in the oil fields would it have been possible to find the necessary equipment, labor and experience immediately available. In the short space of 17 hours after the work was organized, some 2000 tons of debris were picked up piecemeal and hauled away during an all night rain storm; concrete slabs were broken up, tangled steel cut with torches and the smaller fragments that had to be shoveled, were carried off in small baskets and carefully emptied under flood lights to avoid overlooking a hand or foot or any torn portion of a body.

The story broke across the US, and was reported on by journalists from across the country, including a very young Walter Cronkite, working for the United Press in Dallas at the time. Later in life, he recounted: "I did nothing in my studies nor in my life to prepare me for a story of the magnitude of that New London tragedy, nor has any story since that awful day equaled it."

Mother Frances Hospital had just finished construction in Tyler, about 25 miles east of New London. An all-day ceremony, including a ribbon cutting and banquet, had been planned for Friday, March 19. But, when the staff received word of the explosion that Thursday afternoon they decided to open the hospital early. Medical facilities in the surrounding area were overwhelmed with victims, but also with donations and offers to help. In the end, the explosion killed 270 students and 24 adults.

The governor of Texas declared martial law in New London and appointed a team of officials to form a military court of inquiry, and investigators from the state and federal governments got involved as well. Their first job was to rule out potential causes of the explosion. There were rumors that the blast was a result of dynamite. Apparently, workers had been using it to construct a running track at the nearby athletic field. Eighteen sticks of dynamite were stored below the auditorium on the day of the explosion, but they were found intact afterward.

Investigators were confident that gas caused the explosion but were not yet sure of its source. They tested the school’s sewer system for combustible gases but found none. They also drilled more than 70 holes into the soil below and around the school to determine whether gases were seeping up from the ground. Their detectors found no meaningful traces of hydrocarbons. The only possible source was also the most obvious: the natural gas line traversing the crawlspace.

Looking back, there may very well have been warning signs. Students and teachers had been complaining about headaches in the week leading up to the explosion. The superintendent and several board members had, in fact, met the day of the explosion to search for potential sources of the complaints. A school janitor even searched the crawlspace that morning and, struggling to see, lit a match to get a better view. Either the leak didn’t start until later that day, or it hadn’t reached an explosive mixture yet. The residue gas was tested in a lab after the event and found to explode when mixed with air at proportions between around 4 and 13 percent.

All the investigation reports suggested that switching sources from the utility gas to the extraction plant residue line didn’t directly contribute to the explosion. Even though the gas's chemical composition was different, it wasn’t significantly more explosive than the previous supply. And, the regulator should have been able to manage the less reliable pressures coming from the residue line. The Bureau of Mines report concluded that “no appreciable difficulty should have resulted from its use.” But, all the work involved in changing the gas supply was performed by an unqualified crew rather than professional plumbers.

The Texas Inspection Bureau report noted that the school janitors were often “jacks of all trades and probably masters of none” and that they might not have tested for leaks or tightened joints, or they may have just knocked something loose while they were working.

We’ll never know for sure what caused the leak because all the plumbing was destroyed in the explosion. But, the investigations did cite a bunch of factors that magnified the likelihood and severity of the disaster. The crawlspace was large, spanning the entire length of the school, creating a huge volume for natural gas to accumulate. The robust concrete foundation and limited sources of ventilation left no easy paths for the pressure of combustion to escape, making the explosion extra powerful. And most importantly, natural gas is mostly odorless. There was no way to detect a leak. And even the smell of the less-refined residue gas from the extraction plant would have been nearly impossible to notice in a town surrounded by oil wells where the smell of petroleum was just a constant part of life.

But, ultimately, the inquiry found no grounds to charge anyone involved in the disaster. Although the dangers of natural gas were well-known by that time, safety regulations just hadn’t kept pace with its growing use in buildings. The explosion resulted from a number of profound misjudgments, but no laws were broken. Instead of charges, the court issued recommendations to lawmakers to prevent a similar tragedy in the future, many of which were echoed by the other investigative reports. And several of those proposals would forever affect the fields of engineering, plumbing, petroleum production, and more.

Within a few months, Texas passed two sweeping new laws. First, they joined the growing ranks of states requiring the registration of engineers. At the time, anyone could call themselves an engineer and offer services to the public, regardless of their experience or qualifications. The new law created a regulatory board to oversee the licensing process, helping build public trust in the profession and limiting the possibility of unqualified engineers being involved in decisions that affect public safety. Similar laws and licensing would come for the plumbing industry a decade later.

The second major law that resulted from the explosion established regulations for the odorization of natural gas. Many utilities across the country (and elsewhere in the world) were voluntarily adding chemicals to their gas to make it more detectable by smell, but the new law in Texas created standards that would quickly spread through the rest of the US. Only a few months after that law came into effect, Peerless Manufacturing began shipping an odorizer invented by two Texans, one of whom helped in the rescue effort at New London. The Type “M” Oderizer could precisely dispense liquid odorant into a gas stream, accounting for any changes in flow rate and pressure. The device was designated a Mechanical Engineering Landmark by the American Society of Mechanical Engineers in 1992, and odorizers of its kind have likely saved countless lives by making natural gas leaks easily detectable by smell. Odorization got its federal mandate with the passage of the Natural Gas Pipeline Safety Act of 1968, and is now a widely accepted and implemented safety measure across the world. Natural gas is so closely associated with the smell of ethanethiol (commonly known as ethyl mercaptan) that many never know that it is added artificially.

It’s interesting to look back on an event like this with a modern lens and see just how different our world is now. There are so many parts of the story that would have played out so differently within the current system of building codes and licensure and safety measures that we largely take for granted. And that’s a good thing, right? It means that, whether directly like those new laws, or indirectly in a wide variety of ways, we’ve learned from our mistakes. In the face of such a horrific tragedy, countless lives have been saved and accidents have been averted by our ability to reckon with errors and work hard to correct them. It gives me some comfort at least. Natural gas is one of the most important resources on the planet right now. That’s not to say there are no consequences that come with it, and hopefully, we’ll grow less dependent on it over time, but it’s driven countless innovations that benefit nearly everyone in a huge variety of ways. And so, even if you had never heard of New London, Texas before now, you can feel fairly confident that, all these decades later, you’ve also benefited in some way from the hard lessons learned there in 1937.