Physical changes of indoor dust caused by hot surface contact

The aim of this study was to achieve a better understanding of the physical changes of indoor dust as a result of heating. Indoor dust was collected from an office building, and the fine fraction was heated in the temperature range 50–250°C. Characterisation of the dust was performed before and after contact with hot surface with respect to particle size and shape (electron microscope), specific surface area (nitrogen adsorption method), number of particles (optical particle counting, condensation nucleus counting) and weight loss (thermogravimetric analysis). Heat treatment induces a significant increase in the number of emitted sub-micron particles, probably dominated by condensation particles. This occurs even at low temperatures, (50–100°C), which are often present in an indoor environment. Size, shape and specific surface area of the residual dust show only minor differences from non-heated dust. Emitted volatile organic compounds from the same experiments have been reported in a previous study and biological effects are currently being studied.