What is considered a “hazardous area” of a building?

According to the National Fire Protection Association’s Life Safety Code, a hazardous area is an area within a building that poses a degree of hazard greater than normal. This would include those areas used for the storage or use of flammables and combustibles; toxic, noxious, or corrosive materials; or heat-producing appliances.

The hazard level of materials stored in a building is classified as low, ordinary, or high. “Low hazard” contents are those that have such a low combustibility level that they could not support a fire. “Ordinary hazard” contents are classified as those likely to burn at a moderate pace or to give off a considerable volume of smoke. “High hazard” contents are those that are likely to burn extremely quickly or from which explosions are likely to occur.