Eng 525 Responded on a gas leak 100 E. Park (3 Story Bldg.). Eng 525 Found smoke on 1st floor and requested a full alarm. Eng 522, Ladders 551, 554 and BC 505 were added. Gas had built up in a room on 1st floor and was ignited. Ladders 556, 552 were then added to the alarm. Eng 525 and Ladder 551 made an interior attack. Fire was out in 35 min.