Thoracic and respirable aerosol fractions of spray products containing non-volatile compounds.

A versatile and simple mass balance method for the measurement of the release fraction of thoracic and respirable particles of non-volatile compounds of spray products is presented. The release fractions are defined as the ratio between the mass of suspended non-volatile particulate matter in the thoracic and respirable particle size range and the total mass of non-volatile material released with the spray action. For its determination, a spray bolus of short duration and of defined mass is sprayed into a well stirred control chamber. The respirable and thoracic aerosol mass associated with the spray bolus is determined by measuring the time averaged mass concentration inside the control volume and the half time of the exponential concentration decrease to be expected in well stirred systems to correct for mass losses during sampling.  The method is used for a wide range of spray products and technologies for which the release fractions vary by orders of magnitude. A set of data is presented elucidating the relationship between spray technology and fine particle release. Furthermore, a simple rule of thumb was derived from the data that allows for estimation of the release fractions based on a characteristic diameter of the spray droplets. The usefulness of the mass balance method for substance classification as well as for generating input data for exposure assessment and indoor air quality modeling is discussed.