Hi @Krileon, you probably want to do this within your blueprint by destroying the system when the dash is interrupted, though you can do it within your particle system if you need to.
In the spawn rate module, you can set the spawn rate up to a custom bool.
From here, you can go ahead and make a scratch pad to control the bool state.
Here, you can take the owner’s velocity as an input. I’ve added and abs node so all values are positive. Then, you can compare the velocity against your minimum velocity to start the particles, and if your return bool is true, particles will spawn.
This will still produce particles if your player is above a threshold velocity, even outside of the dash. If needed, you can add a Do Once node to make sure there is only one switch between the two states.