What method can be used to keep unusual quantities of coal dust out of suspension?

Applying water or dust-allaying devices is effective in keeping unusual quantities of coal dust out of suspension because moisture helps to coalesce the dust particles, causing them to clump together and settle down instead of remaining airborne. This method directly addresses the problem of dust suspension, which can pose health risks to workers and negatively impact air quality in underground environments.

Dust-allaying devices, such as dust suppression systems, are specifically designed to target dust generation at its source and can significantly reduce the amount of airborne dust. By using these techniques, mines can create a safer working environment where visibility is improved and respiratory hazards are minimized.

The other methods mentioned do not effectively manage coal dust in suspension. Protective gear does not eliminate dust; it merely provides a means for workers to protect themselves from exposure. Increasing the temperature or reducing ventilation could exacerbate dust issues or create unsafe conditions, as both of these actions could increase the concentration of dust particles in the air, potentially leading to higher risks of fires or explosions in an underground setting.