The smallest dust particles and gases are the most dangerous to humans. We divide the gases into organic and inorganic gases and vapors, vapors from acids, and ammonia. Think of gases such as benzene, methane and sulfur. Examples of hazardous dust particles are in particular asbestos and silica (sand). These are released into the air when moving or processing materials. We cannot see these types of airborne particles with the naked eye and are very easily inhaled.