how to initial the amount of particle

I’m trying to make fog in part of an area of my scene. if I use Atmospheric fog will course the whole scene have fog. So I decide to use particle.
How to have all the particles already created initially and stays the whole time? Which means no more adding and destroy particle.

Particle emitter has Spawn module. It has Burst list option. There just add single burst at start that have initial amount of particles. Then make particles to live forever and set spawn per second to zero.

under spawn, I choose rate constant to 0 and rate scale to 0, then Burst list count 1 at time 0, Burst Scale constant to 1, under Lifetime Min and Max 0. But every second, it pop up a new particle