A line of billowing gas 30 feet long and 5 feet wide emanates from you in a direction you choose.  Each creature in the line must make a Constitution saving throw.  On a failed save, a creature takes 2d10 poison damage and is poisoned for 1 round.  On a successful save, a creature takes half as much damage and isn't poisoned.  A creature that doesn't need to breathe is immune to this spell, and a creature that is holding its breath when you cast the spell has advantage on the saving throw. 

At Higher Levels.  When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d10 for each slot level above 2nd.