Step 1 How Much Water is Needed?

Determine the Occupancy Hazard Classification Number

Minimum Water SupplyThe occupancy hazard rating is a way to classify an occupancy with a number that can be used in the formula to determine minimum water suppliesneeded for the structure.

In the formula, the occupancy hazard number ranges from 3 through 7, and the occupancies with a greater hazard receive lower classification numbers. This is because the number is used as a denominator in the formula.

The categories detailed in the following classification numbers should not be used just from the list without conducting a survey of a structure. Hidden factors could change the classification number, and such factors should be discovered during a survey, not during an emergency situation. For example, storage of products that are potentially hazardous from the standpoint of increased fire volume, or those having an explosive nature, exist at many rural locations, and such products can exist in sufficient quantities to increase the occupancy hazard of the building.

The lists below are not all-inclusive. During a survey of an occupancy, individual fire departments may interpret particular circumstances and apply them to the intent of the categories below. Where more than one occupancy is present in a structure, the occupancy hazard classification number for the most hazardous occupancy is used for the entire structure.

No hazard classification is assigned when the building has an automatic sprinkler system installed in accordance with applicable standards.

Occupancy Hazard Classification Numbers

Class 3

Occupancies in this class are considered SEVERE hazard occupancies, where quantity and combustibility of contents are high. Any fire would tend to develop very rapidly and have high rates of heat release.

Examples:

Class 4

Occupancies in this class are considered HIGH hazard occupancies, where quantity and combustibility of contents are high. Any fire would tend to develop rapidly and have high rates of heat release.

Examples:

Class 5

Occupancies in this class are considered MODERATE hazard occupancies, where quantity and combustibility of contents are moderate. Any fire would tend to develop quickly and have moderately high rates of heat release.

Examples:

Class 6

Occupancies in this class are considered LOW hazard occupancies, where quantity and combustibility of contents are moderate. Any fire would tend to develop at a moderate rate and have moderate rates of heat release.

Examples:

Class 7

Occupancies in this class are considered LIGHT hazard occupancies, where quantity and combustibility of contents are low. Any fire would tend to develop at a relatively low rate and have relatively low rates of heat release.

Examples:



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