Hypoxia Zones are areas in Biomutant where you will take damage the longer you stay in them, which can be a problem as some quests will force you to go through them. That said, you can survive in these zones by getting armor that increases your resistance to Hypoxia.
Along with that you can also boost your resistances by getting some bio points. We talked about these special points in length in the guide below, but in short, you will need these points to get mutations and increase resistances. You can also get bio points from killing enemies called biocreeps; morks are an excellent example of one of these enemy types. Finding bio capsules is also a good way to get bio points.
Related: How to get Bio Points in Biomutant
However, you shouldn't waste your precious points on boosting your resistance, as you can get 100 percent resistance by simply getting oxygen armor.
To get this armor, you will need to talk complete the Oxygen Pingdish Quest. Following this quest will eventually send you to a location called Bangshelter 11. Inside this location, you can find the oxygen suit after you deal with some enemies. That said if you need a walkthrough on what to do, check the awesome video linked above from Pure Game Guides.