Carrie Underwood required an oxygen boost during her gig in Colorado on Thursday (14Feb13) because of the venue's high altitude.
The Jesus Take the Wheel star was performing for fans in Broomfield, but before her encore, she headed back to her dressing room in a bid to increase her energy.
Carrie Underwood shared a photograph of herself wearing an oxygen mask with her Twitter.com fans and added, "In high altitudes, they put oxygen in my dressing room under the stage! This is me before the encore."
She later returned to the site to declare, "Thanks, Colorado, for the wonderful energy over the last two shows! I can always tell when I'm in a great place full of great people."