dust

A semi-empirical two-compartment constant parameter model is used to predict airborne and surface du t concentrations. The model parameters are air in- and exfiltration internal particle sources, surface deposition caused by settling. Brownian and turbulent diffusion and thermophoresis track-in of dust particle and resuspension. Model predictions are calculated for some typical scenarios, and the soiling rate of a vertical surface is calculated for a range of friction velocities and electric field strengths.

A new experimental set-up to investigate the physical process of dust deposition and resuspension on and from surfaces is introduced. Dust deposition can reduce the airborne dust concentration considerably. As a basis for developing methods to eliminate dust related problems in rooms, there is a need for better understanding of the mechanism of dust deposition and resuspension.

For exhaust systems that handle dusts, a minimum transport velocity is required to prevent settling and plugging of ductwork. The minimum transport velocity required was studied experimentally for different kinds of dusts. In the case of horizontal ducts, three different velocities related with the minimum transport velocity were measured: saltation velocity, settling velocity and pick up velocity. The experimental results obtained are shown in different graphs, plotting minimum transport velocities vs. particle size and density.

A method was developed to estimate dust production and deposition rates for a ventilated airspace without a recirculation system under steady-state conditions. The method was derived from a dust mass balance equation and parameter estimation method. The measured variables required for using the method were the dust concentrations and ventilation rates of the ventilated space. The outputs of the method were dust production and deposition rates.

In some ventilation and dust removing system of workshop, a great deal of energy is wasted due to heated and cooled indoor air being exhausted directly. So if the dust in the indoor air is removed and then recirculate, the objective of energy saving can be reached. In this paper, the calculation equation of dust concentration, relative humidity in indoor and recirculate air and heater capacity are given along with the control measures to them.

Fungal spore content in dust accumulated in air ducts was investigated in 24 mechanically ventilated single-family houses of which 15 had also a central air heating system. Dust was collected from the ducts simultaneously with cleaning of the ventilation systems. Besides spore concentrations and flora of culturable fungi, total fungal spore concentrations were determined in dust samples by the aqueous two phase technique and spore counting with epifluorescence microscopy.

Many ambient pollutants are in particulate form arid there is a need to sample them for a variety of reasons. A wide range of samplers is available for different purposes but, unfortunately, there does not seem to be a very good understanding of the reasons governing the choice of samplers for different tasks. The present paper attempts to address some of these problems by reviewing briefly the types of sampler used for collecting airborne dust in the ambient atmosphere and the reasons for their choice.