The average house will accumulate 18 k (40 lb.) of dust a year. The dust film that children love to write their names in is made up of particles of more than 5000 different materials, including skin flakes; human hair; pet hair, skin and saliva; food bits; pollen grains; mould spores; insect parts; sawdust and fibre. So it is important to be diligent and effective when it comes to dusting.