What defines explosive dust?

The definition of explosive dust is centered around its ability to create a flammable atmosphere when suspended in air. Fine particles, which are small enough to remain airborne for extended periods, can mix with air to form a dust cloud. This cloud can become ignitable, creating the potential for an explosion if there is an ignition source.

This characteristic of fine particles is crucial in explosion hazards because it highlights the need for safety measures in industries where materials are processed in a way that generates dust. It also explains why managing dust accumulation and controlling particle size are essential in preventing explosive conditions in various environments.

The other options do not capture the essential aspect of explosive dust. For instance, large particles that sink to the ground do not contribute to a flammable atmosphere, and dust that's only harmful when inhaled does not address the explosiveness and ignition risk associated with airborne dust. Additionally, while dust can potentially act as a fuel source, this does not define its explosiveness in the context of dust being a hazard. The emphasis is on the dust's ability to remain suspended in air and form an explosive mixture.