First, a bit of protocol. These fora are not really friendly to IM-speak. You'll get consideration from more people if you spell words like "for" out.
Air is approximately 19.6% oxygen by volume. So if the LEL of methane in air is 5% then you can normalize those two components to 100% and get the LEL of methane to be 20.3% and the UEL would go from the published 15% in air to 43.4% (by volume) in Oxygen.
I,ve found in the literature that for methane; UEL is: 5-15% (in air), and 4-59% (in oxygen). For propane 2,2-9,5% (in air), and 2-48% (in oxygen). Now I only need the same data for ethane...