ABSTRACT
The "settled dust" as used in conjunction with asbestos in buildings was defined in a publication in 1986 as loose fibers and particles that have collected on building surfaces. Although dust is considered to be composed of particles that are small, there is no universally accepted size below which particles are considered to be dust particles. A chart entitled "Characteristics of Particles and Particle Dispersoids" is frequently cited in air pollution to describe the characteristics of particles. In order to understand asbestos in surface contamination, it is useful to have some information about the general nature of dust and debris. Forest fires and other burning may contribute both organic and inorganic particles to the dust. The natural degradation of exterior building materials as they are affected by the elements contributes to the components of dust. Settled dust, accumulations of solid particles that have fallen out of the air, is also referred to as "accumulated dust," and "surface dust”.