A 13-year-old girl from Canada will have a chance Wednesday to thank the city firefighter who saved her life - but not by running into a burning building.

Laura Poelstra, who has been battling a debilitating blood disorder, left British Columbia for the first time so she could meet Mark Mianulli, the hero who didn't think twice before helping out.

"I've got two children of my own so when I heard I'd be helping a kid it became a no-brainer," said Mianulli, 28, who works at Engine 45 in the Bronx.

"I took a job in the Fire Department five years ago to help people," said Mianulli, "and this is another avenue for me to do that."

Two years ago, Laura was diagnosed with severe aplastic anemia, a condition where bone marrow does not replenish blood cells. The illness can lead to death within months if untreated.

Because none of her four siblings were marrow matches, Laura had to receive weekly transfusions of new blood while her family searched for a donor.

Mianulli, who signed up with the New York Blood Center while in the Fire Academy, was told about Laura in June 2007 and underwent a painful operation to give her some marrow.

Almost immediately, Laura's condition improved.

"I have so much more energy now, when I used to always be tired before," said Laura, who has been able to sightsee in New York the past few days.

Today, her family will be introduced to Mianulli at a ceremony at FDNY headquarters.

"We are so very fortunate," said Laura's mom, Francine Poelstra. "We are so lucky that she found a perfect match and that she can resume a normal life."

"We want to say thanks."

jlemire@nydailynews.com