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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Dean<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There are two levels of collection depending on who wants what. We are using a Dusttrak DRX which can measure up to 150 milligrammes per cubic metre. It measures and reports PM 1.0, 2.5, 4.0 and 10 simultaneously. It is a light scattering instrument that can measure down to PM0.1. We also have in JHB a GRIMM 180 aerosol monitor which covers 0.125 to 32 microns in 32 channels.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>In order to collect data from much higher concentrations, the exhaust stream from the stove is captured (or sampled directly from the chimney) and diluted using dry air to get the humidity below the condensation point so as to avoid measuring condensed water droplets as particles. This dilution also considers what the PM level is at the time. It is not a fixed dilution – it can be adjusted at will by an operator. As a result it can cover a range of 2 million to 1 in concentration. LBNL just built a copy of it and said it work right off the bat. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Gravimetric confirmation can be provided when someone really wants the info. Deep quartz filters are preferred because they are far easier to work with and the concentrations tend to be high, and the scale needed is not in the same class as that required for IAQ work. Both Profs Annegarn and Lodoysamba have many years experience with outdoor air measurements so we can set up for anything people want to know. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>We have always been concentrating on stove development and avoiding certification (many difficult issues) so the setup is aimed at real time measurements so as to find sweet spots and develop them. I don’t have a lot of confidence in light scattering especially or small sizes where the detection efficiency is low. There are good machines around which can detect over 1 billion particles per cubic centimeter and characterise the size and shape simultaneously but budget becomes an issue. A stove development lab just doesn’t need that kind of detail.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The big issues for anything using a hood (which we use for small stoves) is the condensation of moisture at low dilution rates because it is reported as PM. Really clean stoves produce so little that the temptation to reduce the dilution leads to problems. That assumes of course that the sample is properly dried / condensed. Condensed particles are probably dominant in terms of health effects. To get the particles to condense and keep the moisture in vapour form is the core challenge.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>We have managed to cope with PM up to 17 grammes per cubic metre (O2 factored to 0%). The was measured during the operation of an ‘improved stove’ that was promoted having never been tested.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>As you probably know, we are using a carbon mass balance method of determining the volume of emissions (scale and diluted sample) so there is normally no hood involved. Even when there is, we do not capture the whole volume of emissions, only a sample + the mass burned. This is quite different from the EPA and PEMS hood method. I can’t really comment on the overall accuracy comparison, but the no-hood method copes better I think with moisture in the stack and can handle massive doses of PM early followed by very low levels later.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Dear Crispin,<o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>How are you measuring PM in your experiments these days: light scattering, pump and filter, or something else?<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Best,<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'>Dean<o:p></o:p></p></div></div></body></html>