# Ppm and flow rate

1. Apr 18, 2007

### hananl

Hi guys,
This question is about the conversion between ppm and flow rate (I know you can't really convert between those two...)
I have been looking on different products in the Internet, concerning the detection of a gas leak from pipes.
It seems that each company is "measuring differently".
Company A claims it can detect 100ppm of methane. (in air)
Company B claims it can detect a flow rate of 1liter/hour of methane. (in air)

How do I translate between the two? one is ppm as for concentration parameter and the other is for a flow rate.
Lets say there is a wind of 10km/hr max.

I thought maybe physicians could help me with that...
10x.

2. Apr 18, 2007

### lpfr

Company B specs is missing something. It would be tolerable if it was 1 litter /(hour * meter^2), but then the methane concentration would be dependent on wind speed (calculus needed). Buy company A.

3. Apr 18, 2007

### hananl

Lets say I email them, and they tell me X gram/(hour*meter^2)
Then what?

4. Apr 18, 2007

### lpfr

If the wind speed is v m/s, in one hour, 3600* v meters long of air would have traversed the squared meter. Then the total volume will be 3600*v cubic meters. If there are x grams, you can compute the numbers of grams per m^3.
Then you may want to know the volume relative concentration. As you know the molecular mass of methane, you can determine the number of moles (not molecules). Then with the formula PV=nRT you can determine the volume (beware the units , bars, pascals, litters and m^3) of methane. Divide this by 1 m^3 and you will have the relative concentration. You can, of course multiply by a million to transform in ppm.
All this can be put in a single formula.

5. May 5, 2010

### sonics

sir,

Please me calculate the flowrate of oxygen gas form with the given data below:

Need oxygen in PPM = 10ppm = 14.1mg/cubic meter (m3)
Capacity of Tank = 100 cubic meter (m3)

I need the flowrate

Sonics