British Standards

Originally published in 2005 then reviewed and amended in 2014 with help from members of the fire service and players in the industry.

BS9251 covers:

• Individual dwellings (houses, flats and maisonettes)

• Houses of multiple occupancy (HMOs)

• Bed and breakfast accommodation

• Boarding houses

• Blocks of flats

• Residential care premises

• Dormitories

• Hostels

The types of property covered vary on size and type of resident and therefore are split into risk categories. These categories range from 1-3.

• Category 1 covers individual dwellings to small blocks of flats (less than 18M high).

• Category 2 covers large blocks of flats (over 18M high) and small residential care homes (10 residents or less).

• Category 3 covers large residential care homes (more than 10 residents) to hostels.

Each category has minimum design parameters which determine the number of heads that should be used to calculate the amount of water and pressure required to run the system. The total number of heads required in any system is dependent on the room sizes, use and area covered by an individual head. Typically, 1 head can cover 25m2 but should not be more than 2.75m from a wall and no closer than 2.4m from another sprinkler head.

• Category 1 systems require a minimum run time of 10 minutes and the calculation should include 1 or 2 heads in the calculation.

• Category 2 systems require a minimum run time of 30 minutes and the calculation should include 1 or 2 heads in the calculation.

• Category 3 systems require a minimum run time of 30 minutes and the calculation should include 2 or 4 heads in the calculation.