Atmospheric density jacket

An atmospheric density jacket, or ADJ, was a garment worn to protect the wearer against thin atmospheres. The First Doctor required Ian to don an ADJ when they first began exploring the planet Vortis.

A key feature of an ADJ was the resipiratory compensator affixed to its breast. Ian likened the compensator to an "advanced oxygen mask". (DW: "The Web Planet") The effective life of an ADJ was only about an hour, after which it had to be recharged. (DW: "The Zarbi")