SCBA (5e Equipment)
From D&D Wiki
A SCBA (Self-Contained Breathing Apparatus) consists of a sealed mask worn on the face connected to a tank full of air. While wearing a SCBA and the air supply holds out, you are immune to inhaled chemicals, toxins, or particles. Unlike a gas mask, a SCBA doesn't filter air, it is entirely self-contained, allowing you to breathe without issue in an environment where there is no air at all, or the air is completely unbreathable (an alien atmosphere that completely lacks oxygen, for example).
An air tank lasts for 3 hours of no greater than moderate activity, after which it must be refilled in order to provide further benefit; reduce the air supply by one minute for every round of intense exertion, including at the start of each of your turns in a combat encounter.
Cost: 75 gp
Weight: 35 lb.