Abstract:
The invention provides an apparatus set up for diluting aerosols; the apparatus comprising: (i) a dilution chamber (1); (ii) an aerosol inlet (2) on one side of the dilution chamber for admitting an aerosol into the dilution chamber; (iii) an aerosol outlet (3) on the same or another side of the dilution chamber through which diluted aerosol particles can leave the dilution chamber; (iv) a diluent gas inlet (4) for admitting into the chamber a diluent gas; (v) a diluent gas outlet (5) through which diluent gas can leave the dilution chamber; (vi) a gas flow maintenance system (6) that provides circulation of the diluent gas through the dilution chamber; and (vii) means for determining the extent of dilution of the aerosol leaving the aerosol outlet. The invention also provides methods of diluting and counting aerosol particles using the apparatus of the invention.
Abstract:
The invention provides an apparatus for charging or altering the charge of gas-entrained particles in an aerosol, the apparatus comprising:(a) an ion generating chamber (1) containing a first electrode (2) for generating a corona discharge, the first electrode (2) being connected to a power supply of sufficiently high voltage to create the corona discharge; the ion generating chamber (1) having an ion outlet (10) through which ions generated by the corona discharge can leave the chamber (1); (b) a particle charging chamber (5) in which charging or altering the charge of gas-entrained particles in an aerosol takes place, the particle charging chamber (5) being in fluid communication with the ion generation chamber (1) and having an inlet and an aerosol outlet; and (c) an electrically non-conductive interface body (7) positioned between the aerosol particle charging chamber (5) and the ion generating chamber (1), the interface body (7) having a hollow interior which is in fluid communication with the ion generating chamber (1) and the aerosol particle charging chamber, and having a gas inlet (8) through which a stream of gas can be introduced into the hollow interior of the interface body (7).
Abstract:
The invention provides an apparatus for increasing the size of gas-entrained particles in order to render the gas-entrained particles detectable by a particle detector, the apparatus comprising an evaporation chamber (2) and a condenser (7); the apparatus is configured so that vapour-laden gas from the evaporation chamber can flow into the condenser and condensation of the vaporisable substance onto gas-entrained particles in the condenser takes place to increase the size of the particles so that they are capable of being detected by a particle detector.
Abstract:
The invention provides an apparatus for increasing the size of gas-entrained particles in order to render the gas-entrained particles detectable by a particle detector, the apparatus comprising an evaporation chamber (2) and a condenser (7); the evaporation chamber (2) having an inlet (1) for admitting gas into the evaporation chamber and an outlet through which vapour-laden gas may leave the evaporation chamber; the evaporation chamber (2) having disposed therein a heating element (3) and a porous support (6), the heating element being in direct contact with the porous support, wherein the porous support (6) carries thereon a vaporisable substance and the heating element (3) is heatable to vaporise the vaporisable substance to form vapour within the evaporation chamber (2); the condenser (2) being in fluid communication with the outlet of the evaporation chamber, and the condenser (7) having an outlet for connection to the particle detector. the apparatus being configured so that vapour-laden gas from the evaporation chamber can flow into the condenser and condensation of the vaporisable substance onto gas-entrained particles in the condenser takes place to increase the size of the particles so that they are capable of being detected by a particle detector.
Abstract:
The invention provides a method for obtaining aerosol particle size distributions with a scanning mobility particle sizer (SMPS) device comprising a differential mobility analyzer (DMA); which method comprises the stages: (i) collecting a first data set of particle concentrations vs. size for a size range from a predetermined minimal size Dmin to an intermediate size Dt by varying a voltage applied to a DMA column of an SMPS from Vmin to Vt1 at a first sheath flow rate Qsh1; (ii) changing the sheath flow rate from the first sheath flow rate Qsh1 to a second sheath flow rate Qsh2; (iii) collecting a second data set of particle concentrations vs. size for a size range from the intermediate size Dt to a predetermined maximum size Dmax by varying the voltage applied to the DMA column of the SMPS from Vt2 to Vmax at the second sheath flow rate Qsh2; (iv) convolving the first data set from stage (i) using an apparatus function of the DMA and the sheath flow rates Qsh1 and Qsh2 in stage (ii); (v) combining the convolved data set from stage (iv) with the second data set from stage (iii) to form a merged data set corresponding to the size distribution from Dmin to Dmax; and (vi) deconvolving the merged data set to provide a size distribution for the full size range Dmin to Dmax. Also provided are a DMA, SMPS or Fast Mobility Particle Sizer (FMPS) apparatus set up to perform the method.