Fire Sprinkler Safety Standard – BS9251

BS 9251 is the main British Standard covering fire sprinklers in this country. BS 9251 gives guidance for the design, installation, components, water supplies and back flow protection, commissioning, maintenance and testing of fire sprinkler systems installed for life safety purposes with additional benefits for property protection in residential and domestic occupancies.

History of British Safety Standards for Fire Sprinklers

The actual conception of a fire sprinkler system was considered by an English inventor, Sir William Congreve, back in 1812. However the world would have to wait until 1874 until the first automatic fire sprinkler system was fitted by American Henry S. Parmalee. Since then fire sprinkler systems have developed, evolved and become more standardised especially in terms of their design, installation and commission.

Taking many aspects from the long established American NFPA fire design codes significant inroads were made in the UK fire sprinkler market with the publication of a full set of British Standards for fire sprinklers in 2004 and 2005. After some 18 months of deliberation these were updated to become BS9251 : 2014. Which came into force on the 31/10/14. There were noticeable changes throughout with a greater emphasis on consultation with Authorities Having Jurisdiction (AHJ’s) to asses risk, run times and design/ discharge density. Previously there were 2 categories of Domestic, and Residential. This became 3 categories numbered 1-3 (see below). Each system is bespoke to the risks including building design or intended inhabitants.

BS 9251: 2021 – British Standard for Fire sprinkler Systems for Domestic and Residential Occupancies.

Specifically for domestic and residential fire sprinkler installations. This standard sets the minimum requirements for the design, installation and commission of a fire sprinkler system. 

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Key features:

  • Minimum flow rates: 60 litres per minute (lpm) through a single nozzle or 42lpm for multiple nozzles.
  • Minimum design: 2 nozzles for domestic and 4 nozzles for residential properties.
  • Minimum duration: 10 minutes for domestic properties, 30 minutes for residential properties.
  • Minimum nozzle spacing’s: no more than 2m from any wall or corner, no closer apart than 4m.

BS 9251: 2021 – Sprinkler Systems for Residential and Domestic Occupancies – Code Of Practice

BS 9251 specifies the design, installation, components, water supplies and backflow protection, commissioning, maintenance, and testing of fire sprinkler systems installed in residential and domestic premises. BS 9251 is applicable for sprinkler protection of domestic and residential premises and contains specific recommendations for sprinkler systems in those premises of more than four stories or above 18 m in height, whichever is the lower.

Note: In buildings where there is a mix of both residential, non-residential and commercial use, it is generally appropriate to protect the residential parts using BS 9251 and the non-residential parts using BS EN 12845.

Category 1 Fire Sprinklers

Covers: Single family dwelling such as individual dwelling house, individual flat / maisonette / transportable home. Houses of multiple occupation (HMO’s). Bed and breakfast accommodation / boarding house. Blocks of flats 18m or less in height and maximum total floor area of less than 2400m2.

  • Calculations must allow for 1 or 2 sprinkler heads operating
  • Average flow 84-100 litres/minute
  • Storage for 10 minutes minimum operation duration
  • Tank size 1m³ to 1.5m³

Category 2 Fire Sprinklers

Covers: Blocks of flats less than18m in height, small residential care premises with 10 or less residents and sheltered and extra care housing.

  • Calculations must allow for 1 or 2 sprinkler heads operating
  • Average flow 84-100 litres/minute
  • Storage for 30 minutes minimum operation duration
  • Tank size 3m³ to 4.5m³

Category 3 Fire Sprinklers

Covers: Residential care with more than 10 residents, dormitories (educational) and hostels.

  • Calculations must allow for up to 2 or 4 sprinkler heads operating
  • Average flow 168-200 litres/minute
  • Storage for 30 minutes minimum operation duration
  • Tank size 6m³ to 9m³

Category 4 Fire Sprinklers

Covers: Blocks of flats 18m and above.

  • Calculations must allow for up to 2 or 4 sprinkler heads operating
  • Average flow 168-200 litres/minute
  • Storage for 60 minutes minimum operation duration
  • Split tank size 6m³ to 9m³ (each tank)

Many factors must be considered when designing a system to BS9251:2014 and full consultation with the relevant AHJ’s.

BS 9251 is the only design standard which Ultrasafe apply for domestic and residential properties which have a pump and tank fire sprinkler system or town mains water fed sprinkler system.

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Fire Sprinkler Specialists

Southern Office

Ultrasafe, Unit 1 Bowlings Corner, Marley Lane, Battle, East Sussex, TN33 0RE

Northern Office

U2 Farriers Court, Horsefair Green, Thorne, Doncaster, South Yorkshire, UK, DN8 5EE

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