If you can smell gas, in all likelyhood you are still well below the flammable limits even the 10% LEL.
If you are within the flammable limits, 4% (40,000ppmV)for methane, in all likelyhood you would not be standingup as you would be either axphyxiated or blown up.
If within 10% LEL, you would be well over the TLV being 1000ppm, so yes get out of the building. There may be a short term (15 minutes) higher exposure limit but I don't know what it is.
So the advices are those from the above responders.