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crpraveen
03-22-2007, 08:49 AM
How to convert %LFL(lower flamability limit) to ppm

Mrs X
03-22-2007, 05:16 PM
If you are looking at flammability data for a gas/gas mixture, then ppm is µL/L. If you have something that says lfl is 10%volume in air, then that is 100,000ppm. If this is not what you are after, please can you provide more info?

crpraveen
03-30-2007, 10:36 AM
If you are looking at flammability data for a gas/gas mixture, then ppm is µL/L. If you have something that says lfl is 10%volume in air, then that is 100,000ppm. If this is not what you are after, please can you provide more info?

Thank you for your reply
That is exactley what I was looking for

Fuel Gas (LEL/LFL) (%) PPM

Acetaldehyde 4 40,000
Acetone 2.6 26,000
Acetylene 2.2 22,000
Ammonia 15 150,000
Arsine 5.1 51,000
Benzene 1.3 13,000
Butane 1.8 18,000
Butylene 1.98 19,800

IS this conversion correct then

Thank you once again

Mrs X
03-30-2007, 12:57 PM
Yes, the conversion is correct. Are you planning on going through the entire alphabet of organics? :) :) :)

Unregistered
02-01-2011, 01:36 PM
1% by volume = 10,000ppm.

Unregistered
04-21-2011, 01:30 PM
Was wondering how best to take this conversion a step further to mg/L? I'm starting with a LFL for a flammable material in air (5.7%) and need to get to mg/L.

JohnS
04-21-2011, 01:40 PM
Was wondering how best to take this conversion a step further to mg/L? I'm starting with a LFL for a flammable material in air (5.7%) and need to get to mg/L.

mg/L will be a problem because the figure will vary as the temperature and pressure change, as that change makes the volume of the mixture change,
The percentage is a ratio of parts per hundred by number of moles of the flamable gas to moles of air mixture. For example 5% means 0.05 mol/mol.
To convert the moles in the numerator, you need molecular weight (molar mass) of the flamable gas (this is a problem for mixtures like gasoline). For the numerator, you need molar volume, which varies with temperature and pressure (at 101.325 KPa, 0 °C, it is 22.414 L/mol; use Ideal Gas Law for other conditions.

Most people use molar ratios for gases to avoid the dependence on temperature and pressure of the control volume (denominator). You could also use mass ratios, but mg/L are very difficult to work with, and temperature/pressure to which the data apply MUST be defined.