Flirting with Danger by Claire Baxter:

*To be together is dangerous. To stay apart is impossible.*Firefighter Jasmine Mackinnon has always just been one of the guys. So no one's more shocked than she is to find herself kissing fellow firefighter and all-around sinfully handsome playboy Aaron Parkes after a friend's wedding. Jasmine knows she can't risk an emotional connection with a colleague—a potentially dangerous entanglement when fighting fires together—and nothing's more important to her than her job.

Aaron never noticed how beautiful Jasmine was until he saw her out of her firefighter duds, but there's something about the fiery woman that tempts him. Though he knows pursuing a real relationship is out of the question for a serial dater like him, when their casual flirtation builds into something more serious, it's not just their jobs or their safety on the line. It's their hearts.