ASTM D7773 Volatile Inorganic Acids

Scope

ASTM D7773 covers the sampling and analysis of volatile inorganic acids in air for the assessment of worker exposure. Air is sampled onto an alkali-impregnated quartz fiber filter and analyzed by ion chromatography to determine the average mass concentration of each acid.

Key aspects of the test scope include:

• Analytes – hydrogen chloride gas and hydrochloric acid mist (as chloride), hydrogen bromide vapor and hydrobromic acid mist (as bromide), and nitric acid vapor and mist (as nitrate)
• Sampling medium – an alkali-impregnated quartz fiber filter that captures and neutralizes the acidic gases and mists
• Analytical technique – ion chromatography (IC) to separate and quantify the chloride, bromide, and nitrate anions collected on the filter
• Result basis – average mass concentration in air (e.g., mg/m³), calculated from the measured anion mass and the sampled air volume
• Sampling duration – suitable for full-period sampling for time-weighted average exposures and for shorter, limited-time (short-term) exposure measurements
• Application context – occupational/workplace air monitoring for worker exposure assessment

Applications

• Occupational exposure monitoring – measuring worker exposure to HCl, HBr, and HNO₃ in workplace air against established occupational exposure limits
• Metal finishing and surface treatment – monitoring acid mists and vapors in pickling, etching, plating, and anodizing operations where these acids are used
• Chemical manufacturing – assessing airborne acid concentrations in processes that produce or use hydrochloric, hydrobromic, or nitric acid
• Industrial hygiene surveys – providing the airborne acid data needed for workplace risk assessments and exposure characterization
• Ventilation and control evaluation – measuring acid concentrations before and after engineering controls (local exhaust ventilation, scrubbers) to verify their effectiveness
• Short-term exposure assessment – measuring limited-duration exposures during specific tasks or operations where short-term peaks are a concern
• Regulatory and safety documentation – generating exposure data to support occupational health programs and worker protection measures

Benefits

• Measures multiple acids in a single sampling approach – chloride, bromide, and nitrate from their respective acids are all captured on one filter type and quantified together by ion chromatography
• Directly supports worker protection – the airborne concentration data is exactly what is needed to compare against occupational exposure limits and assess the risk to workers
• Captures both gas and mist forms – the alkali-impregnated filter collects both the vapor/gas and the acid mist of each analyte, giving a complete measure of airborne acid
• Ion chromatography gives sensitive, selective results – IC cleanly separates and quantifies the individual anions, providing reliable low-level measurement of each acid
• Supports both full-shift and short-term sampling – the method accommodates time-weighted average exposure assessment as well as limited-time measurements for short-duration exposures
• Enables evaluation of controls – before/after measurements provide an objective basis for verifying that ventilation and other exposure controls are working