Some considerations when evaluating physico-chemical hazards of nanopowders

Abstract

The regulatory classification of the physico-chemical hazards of powders is defined in two references, which describe the test methods to be applied, as well as the criteria and the classification thresholds. These two references are respectively the European CLP Regulation and the transport of dangerous goods UN regulation. These two reference systems enable to associate identified hazards with safety rules related to the handling, storage and production of the powders. Traditional microscale powders as well as innovative materials like nanopowders or very fluffy materials need to follow these classification rules. Typically, the properties of interest for nanopowders are related to the reactivity with air and water. The related hazards are defined by the CLP regulation in the following classes: flammability, pyrophoricity, self-heating, water reactivity and oxidizing capability. The hazardous properties of nanopowders can a priori be routinely determined with the regulatory experimental tests performed in an adequate platform like S-NANO at INERIS. However, several aspects were overlooked so far for innovative materials that show specific properties like very low density and high specific surface area. This presentation deals with a review of the limitations of the current tests as well as detailed considerations related to some tests (powder segregation issues, specific ignition issues, safety issues for the operators…). These aspects could perhaps be not thoroughly considered for microscale powders but in the case of nanopowders, these parameters are shown to be of importance in order to evaluate physico-chemical hazards. It is then of primary importance to assess carefully these new behaviors in order to prevent the production of misleading information in safety data sheets