Workers at nine American refinery and chemical plants walked off the job on February 1, marking their first nationwide oil strike in 35 years. By Sunday, the strikes expanded to include more than 5,000 workers at 11 refineries, who are demanding better wages, benefits, and work conditions.

Like most strikes, the workers, represented by United Steelworkers, are asking for a raise. They also want to be safer on the job.

The union accuses oil companies like Shell and BP of keeping operations too lean while oil prices are low, hiring inexperienced non-union operators, and overworking staff. "We're concerned about the excessive overtime," said Lynne Hancock, a spokesperson for United Steelworkers. "In a lot of locations the workers have mandatory overtime. And when people are working non-stop, they get tired and fatigued. And when you are fatigued, you have a tendency to make some mistakes." The rapid expansion of the oil industry has driven up deaths in other parts of the business beyond refining, like extraction. Between 2003-2010, the Occupational Safety and Health Administration (OSHA) reported 823 oil and gas extraction workers died on the job, or seven times worse than the rate for all U.S. industries combined.

Refineries work with super-hot liquids, toxic chemicals, and flammable gasses, making it a workplace filled with potential calamities. In this kind of high-risk environment, a tired staff is more likely to make mistakes. Oil companies know this well: Two of the 11 refineries on strike have seen their own fatal accidents. In 2010, a 40-year-old heat exchanger failed at the Tesoro refinery in Washington state, killing seven. The victims’ families claimed in a lawsuit the company “willfully disregarded” recommendations to make inspections, while they also pushed the heat exchangers for too long. In 2005, an explosion at a former BP refinery (now owned by Marathon) in Texas City, Texas, killed 15 people. In BP’s case, a U.S. Chemical Safety and Hazard Investigation Board later found "organizational and safety deficiencies at all levels of the BP Corporation. Warning signs of a possible disaster were present for several years, but company officials did not intervene effectively to prevent it." The board identified workplace fatigue as one of the possible causes for the explosion. All the operators on shift had worked 12-hour shifts for at least 29 days straight. The report said that the company kept its training operations too lean, downsizing its training staff of 28 to 8, leaving workers unprepared for unexpected conditions.

Fatal explosions at refineries are relatively rare, but there are plenty of other hazards—like pollution caused by a major accident, or leaks that go undetected for a long time. An investigation from NPR found an Exxon plant in Baton Rouge, Louisiana, regularly leaked pollution, including one major pipeline leak in June 2012. That accident released as much benzene as the total amount the Exxon refinery emitted for the two years prior. Nearby residents reported a bad odor for months at a time: They were breathing toxic pollutants. That same year, an explosion at a Chevron refinery in Richmond, California, released thousands of pounds of sulfur dioxide and other pollutants into the air and drove 15,000 people to emergency rooms with breathing problems and heart pains.