Abstract
Pollutants in the indoor environment are a complex mixture of gases, vapours and particles in either liquid or solid phase, suspended in the air, settled or adsorbed on or attached to indoor surfaces. The pollutants originate from a multiplicity of indoor and outdoor sources. The pollutant mixture is dynamic, involved in numerous physical and chemical processes and changing its characteristics with time. Its composition and concentration depend on the strengths of indoor sources, pollutants’ concentration outside and the properties of heating ventilation and air conditioning systems. The spatial distribution of pollutant concentration within the indoor environment is often inhomogeneous.
Particulate matter in the indoor environment includes particles, which are airborne as well as those which are settled on indoor surfaces, dust. The particles vary in chemical properties, which depend on the origin of the particles and differ for particles in different size ranges. The particles can, for example, be combustion or nucleation products, dust or bioaerosols and can act as carriers of adsorbed chemicals, bio-contaminants or condensed gases. Particles are a key component of emissions from all the combustion sources. In particular, a significant indoor combustion product, environmental tobacco smoke (ETS) is a mixture of particle and gaseous products of smoke exhaled to the air by smokers and mixed with the smoke resulting from smouldering of a cigarette between the puffs.
This chapter is focused on particulate matter, its origin, characteristics and behaviour in the indoor environment. In addition, several important classes of indoor pollutants are discussed, those which are entirely or partially composed of particulate matter. These include ETS and combustion products from other sources, such as wood smoke or vehicle emissions, and also fibres, in particular, asbestos.