A firefighter walks through the scene of an explosion Monday, Sept. 16, 2019, in Farmington, Maine. Officials say a town's fire chief is among the injured in a propane explosion that killed a firefighter. State public safety spokesman Steve McCausland said after Monday morning's explosion at a nonprofit center in Farmington that multiple people remain hospitalized. Credit: Robert F. Bukaty | AP

The telltale smell of a propane leak led a maintenance manager to rush people from a building in Farmington where a massive explosion on Monday morning killed one firefighter and injured another six firefighters and the manager.

“The basement was full of propane and it exploded,” said Scott Landry, a Farmington selectman and state representative who was on site all day after the explosion. “It lifted the building right off the foundation.”

He said Larry Lord of Jay was taking firefighters to the basement when the explosion took place.

Landry said office of LEAP, Inc. was rebuilt in a $450,000 project that opened this spring. The town assessor’s office lists the two-story building’s size at 128,000 square feet. The propane system was replaced in the rebuild and the tanks were above ground and outside the building, Landry said.

The explosion in Farmington was unusually large, and could be heard and felt for miles. Propane heat is common in Farmington, along with oil, as the area has no natural gas lines, he said, adding that propane has been considered a safe fuel. Propane is commonly used across rural Maine.

“It’s very rare that there’s an incident of this magnitude,” said Leslie Anderson, president and CEO of the Propane Gas Association of New England.

She said propane systems are not typically connected with pipes unless they are in large industrial complexes.

“So when something happens it involves one location,” she said.

That’s different than the series of natural gas explosions that rocked three communities north of Boston in September 2018 and ignited fires in at least 39 homes, she said.

Propane is a gas created mostly as a byproduct of natural gas processing, although some of it is produced from crude oil refinement.

It is transported and stored as a liquid under pressure, but it is usually used as a gas for anything from heating barbecue grills to heating homes, according to the website Propane Safety First.

Propane has no color or odor, so manufacturers add a strong odorant for safety that some describe as the smell of rotten eggs or skunk spray.

Propane is flammable when it is mixed with air. It also can be ignited by many sources, including open flames, smoking, electrical sparks, cellphones and static electricity. Propane leaks also can cause people to become sick, according to online medical website Medline.

“Every energy source, if not used properly or if there’s an issue, can be dangerous,” said Eric Kuster, vice president in charge of safety, education and compliance at the Propane Education & Research Council in Washington, D.C. About 10 million households nationwide use propane, mostly for heating, and for cooking and running fireplaces.

He said there are no statistics on the incidence of propane explosions nor how often they occur compared to oil or natural gas explosions.

The council recommends that if someone smells the pungent odor of propane, they leave their house or office and get far enough away so they no longer smell propane, and then call emergency services.

Emergency responders usually turn off the propane tank first and then aerate the area. Kuster said it is rare for such a large explosion to occur. Responders have national protocols and local training to prepare for propane and other fuel explosions, he said.