[Shotimes] Re: emissions question

[MonsieurBoo@aol.com]

PPM -- Do I hear any votes for "ratio" or "concentration"?  <g>    
Officially, tailpipe emissions are measured by volume:  1 volume of gaseous pollutant / 
10^6 volumes of tailpipe air = 1 ppm.  As opposed to solids & liquids which 
are measured by weight.

It can be expressed as a percentage, e.g., 1% = 10,000 ppm.  And it can also 
be expressed as an absolute measurement, since if you know the temperature, 
pressure and composition of the exhaust gases you could calculate how many 
molecules of each constituent are in a given volume and hence the fractional weight 
of each, including the pollutants.

Bottom line, I think, let's say we have a lawnmower and a semi trailer, just 
for fun say the semi puts out 1,000 times as much exhaust (by volume) as the 
lawnmower.  They both pass the emissions test with identical ppm numbers, but 
the absolute amount of pollutants coming out the semi's stacks will be 1,000 
times as much as the lawnmower's per each second they are both running.  Which I 
think was the original question.

Cheers,
Mark LaBarre
94 ATX 125k

===================================

ppm is an absolute measurement.

Cheers,
Carl Prochilo
1992 Ultra Red Crimson

Jeremy said:
> Luckily here in Nebraska we don't do emissions testing...but on the
> reports I've seen online, they do them by parts-per-million IIRC.
> Although I guess that is a percentage, isnt it?