From: poutnik@privacy.net   
      
   Dne 08/01/2018 v 01:10 sinclair220@hotmail.com napsal(a):   
   > On Monday, 8 January 2018 00:56:08 UTC+1, sincl...@hotmail.com  wrote:   
      
   >>   
   >> An interesting post Peter, but one question as a layman; Why should the   
   instructions of the co2 detector recommend fixing it onto the ceiling? If   
   butane is heavier than air, should it not be fixed to the wall? It could be of   
   course, badly translated    
   English from the Chinese manufacturer. Appreciate your advice. Rgds Sinclair   
   >   
   > I've found the answer; Butane is heavier than air but Co2 is lighter and its   
   Co2 gas that we are detecting. Apparently, Co2 detectors should be fixed on a   
   wall, not the ceiling because heat that stows above will stop detection,   and   
   the detector    
   should be 15 feet away from the source of heat. Rgds   
   >   
   CO2 is heavier/denser then air either,   
   having about the same molar mass 44 g/mol as propane.   
      
   But the point is - at the same temperature.   
      
   Hot enough CO2 is lighter/less dense than cold air,   
   and additionally, there is not only CO2,   
   but the majority is nitrogen, and also water vapours,   
   that further decrease the density .   
      
   So gases need not to be very hot   
   to be less dense than normal air at ambient temperature.   
      
   The gas from a fire climbs up, not falls down.   
      
   --   
   Poutnik ( The Pilgrim, Der Wanderer )   
      
   A wise man guards words he says,   
   as they say about him more,   
   than he says about the subject.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)