Understanding Units

Craig Spears

November 21, 2006

Part Per …. Dallas?

Some people get so caught up with the specifications that are handed to them or expected of their plants that they lose track of what they really mean. There is very little to put these numbers to a scale that can be really understood.

Here’s a quick try for both parts per million (ppm) and parts per billion (ppb). Imagine looking at the city of Dallas, Texas (or Dublin, Ireland; Edmonton, Canada; Qom, Iran; or Hanover, Germany). Each of these cities have somewhere around 1 million people living in them. Now, realize that a single person in each of these cities would represent approximately 1 ppm.

If you are attempting to get your H2S content down to, say, 8 ppm, this is like singling out 8 people from Dallas. Or 8 people from any of the other cities above (whichever you might be most familiar with).

Similarly, a quick try for parts per billion: imagine a single person in India. Yep – 1 ppb.

Authored by Craig Spears - BR&E Technical Support