On August 20, 2011, about 1800 eastern daylight time, the commercial pilot of a Lindstrand 180A balloon, N75213, was seriously injured while preparing for flight at a park in Lewiston, Maine. Three passengers and one ground crewmember had minor injuries, and three passengers were not injured. The balloon was not damaged. The balloon was registered to Infinity and Beyond LLC and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a revenue, sightseeing flight. Visual meteorological conditions prevailed and there was no flight plan filed. The local flight was originating at the time of the accident. The pilot reported that he inflated the balloon, unstrapped the inflation tank, and prepared a place for a seventh passenger to board the basket. While moving the inflation tank, "the burner hose popped off the tank." Propane gas leaked from the hose, and ignited into a fireball. The pilot sustained second-degree burns to his face and arms and was hospitalized for more than 48 hours. A witness reported that, while passengers were boarding the basket, the pilot bent over and his arm contacted the line of a gas tank. The connection "instantly separated," gas sprayed upward about 6 to 8 feet, and the gas ignited. An inspector with the Federal Aviation Administration (FAA) responded to the accident site and examined the balloon. A rubber o-ring on the inflation tank valve was half-exposed and out of its normal position. The inspector also reported that there was no approval documentation for the installation of the inflation tank. The owner stated that he was unaware that the inflation tank was not approved and would remove it and replace it with another tank that was approved by a FAA repair station.