On Dec. 16, 2016, NIOSH issued new Immediately Dangerous to Life or Health (IDLH) Value Profiles for five more chemicals: diketene, 1,3-butadiene, bromine pentafluoride, methyl isocyanate, and benzonitrile. Each profile summarizes the health hazards of acute exposures to high airborne concentrations of a chemical and discusses the rationale for the chemical’s proposed IDLH value. According to NIOSH, an IDLH value, which is based on a 30-minute exposure duration, is the maximum level above which only a highly reliable breathing apparatus that provides “maximum worker protection” is permitted. IDLH values are established to ensure workers’ ability to escape without loss of life or immediate or delayed irreversible health effects and to prevent severe eye or respiratory irritation or other reactions that would hinder escape. For more information on IDLH values, visit the NIOSH .