New NIOSH Methods for Sampling and Analysis of Airborne Inorganic Acids

Abstract

Acid gases/vapors and aerosols are highly corrosive and can irritate the eyes and mucous membranes of the nose, pharynx and respiratory tract, even at low airborne concentrations. Hydrofluoric acid (HF), hydrochloric acid (HCl), nitric acid (HNO3), hydrobromic acid (HBr), sulfuric acid (H2SO4) and phosphoric acid (H3PO4) are used widely in industrial processes such as ore extraction, metal processing, pickling, electroplating and myriad other chemical processes. It is common for several of these acids to occur simultaneously in the air of occupational settings. Applicable occupational exposure limits (OELs) for these substances in air generally range between 0.1–10 mg/m3 for the various acids.(1) The physical states of the different acids in workplace atmospheres may vary from liquid aerosols (mists) for nonvolatile acids like H2SO4 to gases/vapors for volatile acids such as HCl or HNO3. Procedures for sampling and analyzing inorganic acids in workplace air must take into account the physical state(s) of the target analyte(s). Hence new NIOSH methods for sampling and analysis of inorganic acids in workplace atmospheres, methods 7906, 7907 and 7908,(2) have been promulgated to account for the collection of inorganic acid gases/vapors and/or aerosols. The technical contents of these new NIOSH methods are based on related recently-developed International Organization for Standardization (ISO) consensus standards.(3)