A 35-year-old woman is admitted to the burn unit 4 hours after sustaining a thermal injury to her face, neck, and bilateral upper limbs from a kitchen fire. Examination reveals: blistering erythema with blanching on the face and neck; deep red, leathery, non-blanching skin with eschar on both forearms; singed nasal hairs; and hoarseness of voice. Estimated TBSA is 28%. What is the depth of burn on the forearms, and what is the priority intervention for the airway?