Under what conditions might combustible dust become hazardous according to Class 2, Division 1?

Combustible dust becomes hazardous under certain conditions, particularly highlighted by the presence of mechanical failure. Mechanical failures can lead to conditions that release or expose combustible dust into the environment, increasing the likelihood of ignition sources interacting with the dust particles. This can lead to explosive or fire hazards, making it critical to manage dust accumulation and ensure that equipment is functioning correctly to prevent such failures.

The other conditions listed do not inherently contribute to the hazardous nature of combustible dust. Storing combustible dust alone does not pose an immediate hazard unless there are additional factors, such as accumulation or an ignition source nearby. Proper ventilation is essential for minimizing dust concentration, but it does not eliminate hazards if other conditions are present. Storing combustible materials in closed containers can help mitigate hazards but does not directly relate to the conditions that classify dust as hazardous as described in Class 2, Division 1 standards. Therefore, mechanical failure is significant in recognizing potential ignition sources for combustible dust.