Thin Air (PSR Supplement)

**PSR** is an alternate ruleset that is compatible with most 5e content.
System Differences The Basics PB: Proficiency Bonus Advantage & Disadvantage Reroll Bonus Dice Ability Check Group Check Contest Passive Check Save Ability DC Ability Scores Strength Dexterity Constitution Intelligence Wisdom Charisma Skills	Encounters Group Turns Round-Table Turns Staggered Turns Your Turn Move Action Bonus Action Reaction Making an Attack Unarmed Strike Sunder Cover Communication Hit Points & Damage Hit Points Hit Dice Temporary Hit Points Massive Damage Damage Types Damage Resistance Max Damage	Time Phases Rest Break: a short rest Camp: a rough long rest Downtime: a cozy long rest Downtime Trading Downtime Activity Environment Common Hazards Extreme Climates Peculiar Traits Resistance Immunity Vulnerability Special Senses Defeat Dramatic Death Conditions	Items Carry Capacity Goods & Currency Optional: Material Goods Consumables Weapons Improvised Weapons Attire & Shields Tools Gear Attunement Objects Damaging Objects Hauling Objects Vehicles Optional: Artillery NPCs Attitude Mount Cohort Stat Blocks

Thin air is an extreme climate. It can be difficult to breathe at high altitudes and in ventilation-deprived caves, among other locations.

At the end of each phase a creature spends working or traveling in thin air, it must succeed on a DC 10 Constitution save or lose a Hit Die.

You needn't make this save if any of these apply:

You have no need to breathe.
You are immune to the Suffocating condition
You can consistently hold your breath for 10 minutes or longer, due to a feature.
You are acclimated to thin air.