Uninterrupted air supply is provided by the trolley-mounted cylinder( s) to the wearer via a hose reel. As the air-trolley can be easily re-located and therefore positioned in a safe zone which is in close proximity to working area, the user need only wear a lightweight harness during operation. This allows the wearer a greater freedom of movement, and less stress and fatigue than they would be subjected to if wearing a conventional self contained breathing apparatus unit. The air-trolley is able to accommodate up to four compressed air cylinders of up to 12 litres in capacity and is constructed from an anti-static powder coated steel material. The trolley hose reel connector is protected with a cover to minimize inadvertent damage being caused. The system incorporates a safety pressure relief valve and the pressure reducer is shrouded in a protective plate for additional safety. Application: Chemical tank cleaning, toxic spillages or certain tasks when working on offshore installations