Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2001

Units Conversion Problem

Q. How would you convert lbs/hr to ppm or ppmvd? Any information would be greatly apprecitaed. Thank you.

A. Thanks for your question. Before I can answer, please confirm your understanding of the term "ppmvd".

In any case, you cannot convert lbs/hr to ppm as the first term relates to weight of something (such as a contaminant) per unit of time, whereas the second is the concentration of the "contaminant" either by weight or by volume. ppm = parts per million.

Hence, to help you we need to have the same type of units. For instance, if you are dealing with a powder, we would need the weight of the powder per weight of the carrier (such as air or water), or weight of the contaminant per volume of the carrier. You must specify whether the concentration is by weight or volume. ppmv = part per million by volume.

As soon as I get your response I'll try to help you further. Please try to be as specific as possible.