In this paper we present an extension to the classical particle system. We unify particles, particle sources, and force generators into a second order particle system. In the second order particle system the particle sources and force generators are subject to the forces as well as visual particles. This fundamental change, along with suitable set of force classes, enables us to create better real-time simulations of fire, smoke, clouds, and explosions. We use hierarchical spatial subdivision to reduce the computational workload.