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</o:shapelayout></xml><![endif]--></head><body bgcolor=white 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 Rajan<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'>I bit more investigation shows that it appears to be a number related what was a common test for smoke density ‘back in the day’ when PM detection was very difficult. They are called ‘obscuration’ meters. A light would shine across the chimney and if the light was obscured by smoke it was deemed to be ‘smoky’. This later translated into a particulate load that controlled purely by dilution. If you were emitting too much as a <i>concentration</i> you had to blow extra air into it to reduce the environmental impact. That later evolved into total mass emitted.<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'>If you find a standard that is based on mass alone, then it is one of those earlier standards which were based on early attempts to reduce environmental impact of the ‘dosing’. There are many old stove standard based on obscuration including South Africa’s SANS 1111 which is presently up for consideration for review.<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'>These numbers are not translatable into the IWA approach which is based on either the PM mass emitter per unit of energy released (mg/MJ) or per mass of fuel burned (a preference in the US where most emissions are mg/kg burned.<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 mass per mass burned is not at all convenient for stoves because if you change fuels (and there are lots of different fuels for stoves) you have to set different emission rates to be equal to the other fuels. On a mass per MegaJoule basis you can make comparisons across a spectrum of fuels and conditions.<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'>My earlier comments still stand: the concentration (mass per meter<sup>3</sup>) has no meaning if you don’t know the number of cubic metres, and the concentration in a room has no meaning if you don’t know both the fuel burn rate and the rate of air changes per hour. The latter is quite easy to model if you have the performance of the stove and fuel combination well characterised and you know the range of air changes you want to investigate.<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'>Best 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><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Dear Crispin,</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Bureau of Indian Standards ( BIS ) gives 2 mg/m3 as the upper limit for particulate matter ( PM ) emissions from a wood stove.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Could you please help me with the Norms set by WHO for PM from a wood stove ? Are the Norms a little more liberal ?</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Regards,</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Rajan</span><o:p></o:p></p></div></div></body></html>