Sure you can make it inactive:
1) Set the particle to "Continuous spray" in the object type properties.
2) In the particle actions, under "Particle Spray" use the "Set spraying" action and set to "Not Spraying".
If you are using it as an engine flare then you will also want to add the pin behaviour to the particle object, move it to engine at the start of the layout and pin it to the engine.