Fire engineering's roots date back to Ancient Rome, when the Emperor Nero ordered the city to be rebuilt utilizing passive fire protection methods, such as space separation and non-combustible building materials, after a catastrophic fire. The discipline of fire engineering emerged in the early 20th century as a distinct discipline, separate from civil, mechanical and chemical engineering, in response to new fire problems posed by the Industrial Revolution. Fire protection engineers of this era concerned themselves with devising methods to protect large factories, particularly spinning mills and other manufacturing properties. Another motivation to organize the discipline, define practices and conduct research to support innovations was in response to the catastrophic conflagrations and mass urban fires that swept many major cities during the latter half of the 19th century (see city or area fires). The insurance industry also helped promote advancements in the fire engineering profession and the development of fire protection systems and equipment.