A heat application apparatus includes a longitudinally split cylinder that may be disposed about a section of a suspension bridge cable or similar tubular article. The cylinder is split into two essentially identical semi-cylindrical halves which are pivotally connected by an elongate hinge. A plurality of toggle clamps are arranged transversely across the opens ends of the halves and may be engaged to positively connect and lock the edges together. On each of the inner faces of the halves is secured a semi-cylindrical air bladder. The bladders are covered by a flexible heat blanket having a uniformly distributed electrical resistance heating element. Independent air pressure regulators which are supplied with compressed air provide air at low pressure to the bladders and a suitable electrical connector all reside on the exterior of the apparatus. Optionally, an air compressor may be mounted on each half to supply each regulator and bladder independently, thereby configuring the apparatus so that it requires only electrical power to operate.