Any combustible material can burn at a more rapid rate when in a finely divided form. For example sawdust will burn much faster than a 2×4 piece of lumber. If that dust is floating through the air with the right concentration, it could essentially light the air around you on fire, changing from combustible to explosive. Even materials that won’t burn in larger forms such as aluminum or iron, in the proper conditions, like metal shavings, can be explosive. Even food can be a hazard in dust form at high concentrations (candy, sugar, flour). That’s why the proper precautionary measures need to be taken, just as with Silica dust. There are vacuum attachments to pick up any sawdust or metal shavings. Regular sweeping should occur in work areas where a lot of dust is produced, keeping in mind for the sweeper to use proper protective masks and that the surrounding workers are aware and protected as well.