Three New IDLH Profiles Available from NIOSH

NIOSH recently published new immediately dangerous to life or health (IDLH) value profiles for hydrogen chloride, hydrogen bromide, and hydrogen iodide. IDLH values represent the maximum level above which workers should not be exposed without respiratory protection. They are based on the effects that might occur from 30-minute exposures and are intended to ensure workers can escape from a contaminated environment if respiratory protection fails.

The IDLH value for hydrogen chloride (HCl) is 45 ppm, equivalent to 67 mg/m3. HCl is commonly used for fumigation; in manufacturing of acrylics, synthetic rubber, plastics, and dyes; hardening of steel and iron; and mining. The NIOSH recommended exposure limit (REL) and OSHA permissible exposure limit (PEL) for HCl are 5 ppm as a ceiling value. ACGIH has a Threshold Limit Value (TLV) of 2.98 ppm, also as a ceiling value.

For hydrogen bromide (HBr), NIOSH set an IDLH value of 35 ppm or 116 mg/m3. Its uses include synthesis of bromine-containing compounds, as a solvent for mineral ores, and as a cleaner for mineral residue. The NIOSH and OSHA exposure limits for HBr are 3 ppm, as a ceiling value for the REL and as a time-weighted average for the PEL. The TLV for HBr is 2 ppm as a ceiling value.

The IDLH value for hydrogen iodide (HI) is 45 ppm or 70 mg/m3. It is used as a reducing agent; in the manufacture of pharmaceuticals, iodine salts, and iodine-based disinfectants; and in analytical chemistry. No exposure limits for HI have been developed.

For all three compounds, short-term exposure to dangerous levels can cause eye irritation, coughing, and difficulty breathing. As levels increase, exposure can lead to nose and throat pain, asthma-like symptoms, lung injury, and fluid in the lungs.

More information about NIOSH IDLH values is available from the agency publication “Current Intelligence Bulletin 66.”