Wondrous Item, uncommon
Found in a small container, this powder resembles very fine sand. It appears to be dust of disappearance, and an identify spell reveals it to be such. There is enough of it for one use.
When you use an action to throw a handful of the dust into the air, you and each creature that needs to breathe within 30 feet of you must succeed on a DC 15 Constitution saving throw or become unable to breathe, while sneezing uncontrollably. A creature affected in this way is incapacitated and suffocating. As long as it is conscious, a creature can repeat the saving throw at the end of each of its turns, ending the effect on it on a success. The lesser restoration spell can also end the effect on a creature.
Notes: Incapacitated, Control, Debuff
You are forgetting one very important Rule in D&D and that is that rounds of combat are 6 seconds. You are correct in the fact that someone with a con of 14 would have 3 minuets that they could hold their breath, but that isn't three rounds to try and beat the DC15 con save its 30 rounds, to try and save before they would run out of breath. Then subsequently have 3 rounds after they go unconscious to try and get revived before death.
This would make fun (for the DM) loot from a vampire's servants when prepping for a raid on the vampire. Vampires don't need to breathe, but party members usually do.