How deadly is Dust of Sneezing and Choking?

Question

Dust of Sneezing and Choking is a magic item that can be fairly debilitating to low-Constitution characters, but I'm curious how dangerous it is to inhale this stuff. In particular:

...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...

It seems like this could be quite fatal given that the rules for suffocating say::

When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its Constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can't regain hit points or be stabilized until it can breathe again.

...and once it falls unconscious, it is no longer able to make saving throws against the dust:

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.

How likely is it for creatures of each Constitution modifier to survive an encounter with Dust of Sneezing and Choking?

Answer 1

It can be quite deadly but not really to higher Constitution creatures

Do note, the character is only making a couple of saves before falling unconscious and dying with a state that prevents stabilization (guaranteeing death eventually in most cases):

[The suffocating creature] can't regain hit points or be stabilized until it can breathe again.

Essentially, you just need to check to see the likelihood that the creature succeeds on a saving throw before falling unconscious.

If the effect begins on the creature's turn, they will get one additional save, so you get the following two tables with formula below each (ignoring any other effects that would change the save chance):

On the creature's turn:

\begin{array}{c|c} \text{C = Con mod} & -2 & -1 & 0 & 1 & 2 & 3 & 4 & 5 & 6 \\ \hline \text{P = Chance to die} & \text{64%} & \text{56.3%} & \text{49%} & \text{42.3%} & \text{21.6%} & \text{9.2%} & \text{3.1%} & \text{0.8%} & \text{0.2%} \\ \hline \end{array}

$$P = \left(\frac{14-C}{20}\right)^{1+MAX(1,C)}$$

Before the creature's turn:

\begin{array}{c|c} \text{C = Con mod} & -2 & -1 & 0 & 1 & 2 & 3 & 4 & 5 & 6 \\ \hline \text{P = Chance to die} & \text{80%} & \text{75%} & \text{70%} & \text{65%} & \text{36%} & \text{16.6%} & \text{6.3%} & \text{1.8%} & \text{0.4%} \\ \hline \end{array}

$$P = \left(\frac{14-C}{20}\right)^{MAX(1,C)}$$

Lesser Restoration

Do keep in mind, of course, that lesser restoration is an easy solution to this situation:

The lesser restoration spell can also end the effect on a creature.

Make sure your clerics prepare this spell if it is a frequent tool of the villains you are up against.