A lack of training to fight a wind-driven fire, the lack of a sprinkler system, inadequate staffing, and an inadequate assessment of risk were factors in the deaths of two Boston firefighters in a 2014 blaze that tore through a Back Bay brownstone, according to a federal report.The National Institute for Occupational Safety and Health released a 77-page report —and the Boston Fire Department released its own findings — detailing the events that led to Lt.