In a large sauté pan over medium-low heat, cook the bacon until crisp. Using a slotted spoon, transfer the bacon pieces to a paper towel-lined plate to drain and reserve the bacon drippings.
While your bacon cooks, air pop the popcorn into a large bowl & set aside.
Melt the butter in a medium saucepan over medium heat & add 2 Tbsp reserved bacon drippings. Stir in the brown sugar, corn syrup and salt. Bring the mixture to a boil, stirring constantly. Then, without stirring, allow the mixture to boil, undisturbed, for 4 minutes.
Remove the caramel from the heat and carefully stir in the baking soda and vanilla extract. The caramel will bubble vigorously once you add the vanilla.
Immediately pour the caramel evenly over the popcorn, stirring to coat the popcorn, add the bacon & pecans – stir to combine.
Transfer the coated popcorn onto two, parchment lined sheet pans. Bake the caramel corn for 1 hour, stirring every 15 minutes.
Remove the caramel corn from the oven allow it to cool completely before breaking it into pieces and serving.