Hiho Iain,
I modded the particle-demo (the one with the building and the smoke inside) for my Dark-Physics-Competition-Game and tried something like that (in the original demo they used this way for deleting the Emitter, too!):
phy update 1 rem stops the physics-sim (I understood it that way!)
phy delete emitter smokeEm rem smokeEm is the ID for my `emitter, so in your case there might be a number or something
Maybe that helps
Hoozer
Athlon 64X2 4800+ (939);
2GB DDR-400;
GeForce 6800LE (@12 Pixel-Shader-Units, 6 Vertex-Shader-Units; GPU: @ 380 MHz, RAM: 434 MHz)