A retired firefighter has sparked a firestorm of support since posting a plea on Facebook for help in recovering the helmet he wore in the 9/11 attacks.

The helmet was stolen from the Westbury, L.I., home of Michael and Rebecca O'Connell, both 39, along with their daughter's birthday gifts, his fire fighting medals and a slew of fire fighting memorabilia, in a 2012 burglary. 

The helmet, bearing Michael's Ladder Co. number, 142, and badge number, 4073, was freighted with significance, as it was on his head when he responded as a probie to the collapse of the World Trade Center towers on 9/11. 

The former fighter's Facebook plea had been shared more than 265,000 times by Thursday evening.

"They're searching eBay! They're searching Craigslist! They're all over the Internet," trying to locate the treasured helmet, marveled O'Connell, who was stunned by the outpouring of support from strangers and the ensuing media siege. 

O'Connell, 39, who served as an NYPD officer in Brownsville before joining the FDNY just five months before 9/11, was forced to retire after he was diagnosed in 2007 with sarcoidosis, an inflammatory disease that attacks the lungs and lymph nodes. 

The couple reported the items --  which included Christmas ornaments in the shape of fire trucks and O'Connell's FDNY medals --  missing in August 2012, after discovering they had been taken from their attic while their home was undergoing renovations. 

Nassau cops interviewed construction workers who had been on site, but made no progress solving the case. 

On Tuesday, the now full-time dad to Aidan, 8, Alexandra, 3 and Colton, 6, put a picture of Aidan wearing the hat as a tot on his Facebook page, noting the theft and saying, "I know it's a long shot but if enough people share it maybe it turns up or is sent back so I can keep it in my family."

NYC Fire Wire, a Facebook page devoted to keeping people informed about local fires, picked up O'Connell's plea and promptly ignited an international Internet conflagration of amateur sleuths and citizen detectives.

Commenters from Atlanta to Australia expressed sympathy and pledged to help O'Connell recover his missing lid. "If I see it on eBay or any other place, YouTube twitter etc. I'll buy it and contact you ... fellow 9/11 responder ..." wrote Christopher Holmes. 

Another woman noted that her father's FDNY helmet was stolen in Michigan and was traced to Canada and Europe before cops told her dad they'd found it: "Sharing on Long Island and prayers to St. Anthony!!!" wrote Kathy Ferrari. 

The support -- much of it from other firefighters and fire fighting family members -- reminded O'Connell of just why the battered relic was so profoundly important to him. "There's no better job in the word than to be an FDNY firefighter," said O'Connell. "I miss my brothers. I miss my (FDNY) family. Firefighters always have each other's back: It's just amazing," he said. 

"We're very hopeful now, to see how this has taken off," said O'Connell's wife, Rebecca, a client relationship manager for a bank. 

The helmet was tremendously symbolic to her husband because it was "the one tangible thing he had that he could pass down to our boys and maybe our daughter." Being forced to retire from the FDNY for medical reasons thought to be connected to his job "has been very, very tough on him," but the abrupt avalanche of support has been tremendously uplifting, Rebecca said. 

"This is hitting me all at once: It's just incredible," said Michael O'Connell. 

The couple have their hopes raised that the helmet may eventually find its way home. And if citizen sleuths can find a stolen item that Nassau cops could not, O'Connell, a former cop as well as a former firefighter, won't complain. "They have a tough job to do as well: I don't hold any grudges over who can't find what," O'Connell said. 

Should anyone have his hat, "just throw it on my front lawn! I don't care! I'll even purchase it back!" no questions asked, he promised.

O'Connell wishes he had thought to socialize his search for the helmet earlier "but I'm not that computer savvy. I was just using (Facebook) to share pictures of my family."