A USA TODAY Network investigation works to uncover details about accidents at biolabs where experiments are done with deadly pathogens. The labs are largely self-policing and often secretive when accidents occur. USA TODAY Encased in spacesuit-like gear needed to protect them from the world’s deadliest viruses, four scientists at the Centers for Disease Control and Prevention stepped into their lab’s decontamination chamber where a shower of chemicals was supposed to kill anything on them and make it safe for them to exit into an adjacent changing room. But the shower wouldn’t start, and warning lights appeared as a cascading series of safety systems began to fail inside one of the world’s most advanced biosafety level 4 labs. That's the highest level of containment and security, reserved for work with deadly Ebola and smallpox viruses and other pathogens that lack vaccines or reliable treatments.