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LFL to ppm

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  • LFL to ppm

    How to convert %LFL(lower flamability limit) to ppm

  • #2
    Re: LFL to ppm

    If you are looking at flammability data for a gas/gas mixture, then ppm is L/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?

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    • #3
      Re: LFL to ppm

      Originally posted by Mrs X
      If you are looking at flammability data for a gas/gas mixture, then ppm is L/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

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      • #4
        Re: LFL to ppm

        Yes, the conversion is correct. Are you planning on going through the entire alphabet of organics?

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        • #5
          Re: LFL to ppm

          1% by volume = 10,000ppm.

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          • #6
            Re: LFL to ppm

            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.

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            • #7
              Re: LFL to ppm

              Originally posted by Unregistered View Post
              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.

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