The Chemical-Engineering model describes how the synergetic combination of chemical and engineering factors determines gas, particulate, and hybrid explosion behavior. Explosion behavior is expressed as explosion sensitivity (e.g. probability of explosion), explosion severity (e.g. adverse effects of explosion), and explosion types (deflagration or detonation). Chemical factors are ranked using NFPA methodology. Engineering includes whether explosion occurs in open or enclosed spaces, equipment shape/size, and initial T, p, and flow conditions. The model is semi-quantitative; its virtues are its unique integration of chemical and engineering factors in determining explosion risk, its didactic qualities, provision of insight, and practical utility to engineers who are not experts in combustion science.