Identity and industrial use
Nitric acid, HNO3, has CAS number 7697-37-2. INRS lists fertiliser manufacture, chemical processing and metallurgy. Different formulations and concentrations exist; some fuming presentations contain dissolved nitrogen dioxide. Record the actual product rather than only the acid name. An assessment for a laboratory reagent does not necessarily represent an industrial bath or a reaction stage involving different quantities and conditions.
Two hazards acting together
Nitric acid can cause burns and respiratory injury, while its oxidising capacity favours dangerous reactions with combustible or reducing materials. The acid being non-combustible does not mean it cannot contribute to a fire. Review containers, surfaces, waste and adjacent substances using specific compatibility information. Grouping together every product with acid in its name does not resolve safe storage design.
The process can add gases
Heating, decomposition and certain reactions with metals can release nitrogen oxides. Measuring only the initial reagent may therefore miss an important contaminant. Process analysis should establish what can form under actual conditions. Changes in temperature, feedstock or concentration require review of secondary products as well as the performance and suitability of installed extraction and containment systems during the changed operation.
Exposure and incident response
Intense inhalation can cause serious lung injury whose effects are not always immediate. A significant incident needs the planned response and urgent medical assessment rather than waiting to see whether discomfort disappears. Emergency preparation must also protect people assisting. This information does not replace a clinical protocol or authorise entry into an atmosphere that may contain hazardous concentrations or other dangerous conditions.
Task-specific controls
Prioritise contained systems, capture at the emission point and compatible materials. Examine opening, sampling and component removal alongside the main process. Splash-protection selection should consider concentration and contact duration. Mixing, dilution and reaction operations need their own technical procedures; they should not be improvised from a general hazard description or instructions prepared for another acid or concentration.
Evidence for improvement
Keep identity, concentration, operating conditions and anticipated contaminants with assessment results. Verify control performance during infrequent tasks and after maintenance. Applicable limits and health surveillance require professional judgement and current sources. Do not assign classifications from other acid-mist processes without checking the substance and context evaluated. A documented review should make clear which hazards were actually assessed and which remain to be investigated.
