Pat Reischmann asserted: The gas motor's emit a much more "noxious" odor called carbon monoxide. Gary responds: Indeed the gas exhaust is noxious. Diesel is pretty stinky too. BTW carbon monoxide is odorless, tasteless, about the same density as air (unlike carbon dioxide which is significantly heavier and can dangerously pool in contained low spaces excluding oxygen). So, although it is present in both exhaust brews, and is toxic in each (I posted a long drone about that a couple of days ago), it is not the stinky component. Thanks to Roger Bingham's post today which lists some of the major chemicals: carbon (soot); nitrogen; water; carbon monoxide; aldehydes; nitrogen dioxide; sulfur dioxide; polycyclic aromatic hydrocarbons, the first four and the nitrogen dioxide are odorless (other than the other stuff adsorbed onto the soot particles), while all the aldehydes, most of the gaseous sulfur compounds (like mercaptons in particular), and so far as I know all the aromatic hydrocarbons are particularly smelly. There are smaller amounts of hundreds of other distinct chemicals in there too, and many of them are smelly -- even in tiny concentrations (particularly the incredibly pungent cat box smelling mercaptons I mentioned before). <snip> Pat also said: Modern common rail diesels don't smoke or smell at all. Gary responds: Sorry man, I just can't that one get by! Some folks seem to think that their own **** doesn't stink either...;-} My six year old Farymann on the genset smokes and smells just like a diesel, and my Yanmars do too. OK, spiffy modern diesels do a much better job than say a slobbering old DD 6-71, but they all have similarly smelly and sooty exhaust, differing chiefly in quantity nowadays. <snip the reminder about putting Volvos outdrives on in place of the outboards in spite of cost and weight penalties> Mister Science strikes again... AKA Gary Bell