Dashing

Dashing A PC can freely use the Dash action a number of times equal to 3 + its Constitution modifier. Each additional Dash action it takes during a chase or battle requires the creature to succeed on a Constitution Save (starting at DC 10 and increasing by 1 for each subsequent save) at the end of its turn or gain one level of exhaustion.
Any dashing that occurs before a short or long rest and after needing to make a CON Save because of a previous dash will continue to need to make the CON Save (with escalated DC) even if it is not part of the same chase or battle.
A participant drops out of the chase if its exhaustion reaches level 5, since its speed becomes 0. A creature can remove 2 levels of exhaustion it gained during the chase by finishing a short rest or all levels of exhaustion it gained this way with a long rest.