6.1 General

NOTE There is a minimum package of fire protection measures and management levels associated with each of the risk profiles. These are identified throughout this British Standard.

a) Purpose of Risk Profile:

● To determine appropriate means of escape (Section 5) and life safety design features (Section 7).

b) Components of Risk Profile:

● Reflects occupancy characteristics (6.2 and Table 2).

● Reflects fire growth rate (6.3 and Table 3).

● Expressed as a combined value of these elements (6.4 and Table 4).

c) Consideration of Building Uses:

● Different uses within the same building may have varying fire load densities and occupancy characteristics.

6.2 Occupancy characteristic

The occupancy characteristic is principally determined according to whether the occupants are familiar or unfamiliar with the building and whether they are likely to be awake or asleep. Occupancy characteristics should be determined in accordance with Table 2.

NOTE It is recognized that within each of these categories there will be persons with a range of capabilities present. In some cases, these will be known to the premise’s management. Further guidance is given in Clause 45.

Table 2 Occupancy characteristics

Occupancy characteristics	Description	Examples
A	Occupants who are awake and familiar with the building	Office and industrial premises
B	Occupants who are awake and unfamiliar with the building	Shop, exhibitions, museums, leisure centers, other assembly buildings, etc.
C	Occupants who are likely to be asleep.
Ci A)	long - term individual occupancy	Individual flats without 24 h maintenance and management control on site.
Cii A)	Long- term managed occupancy	Serviced flats, halls of residence, sleeping areas of boarding schools
Ciii	Short- term occupancy	Hotels.
D B)	Occupants receiving medical care	Hospitals, residential care facilities.

NOTE 3 The statutory fire risk assessment can be extended to cover the needs for protection of buildings and their contents as well the prevention of environmental damage and also for business continuity.

a) Occupancy characteristics Ci and Cii are included for completeness within this table but are covered in more depth in BS 9991.

b) Currently occupancy characteristic D, medical care, is dealt with in other documentation and is outside the scope of this British Standard.

6.3 Fire growth rate

The fire growth rate is the rate at which it is estimated that a fire will grow. Fire growth rates should be categorized in accordance with Table 3.

An assessment of the likely fire growth rate should be carried out for every premise. Where available, justification should be provided in selecting a specific fire growth rate.

NOTE 1 This is especially the case in warehouses and similar facilities since there is a wide range of materials that can potentially be stored and the fire growth rate can vary considerably.

NOTE 2 A building with a high fire load density will not necessarily have a rapid-fire growth rate, and low fire load density will not necessarily have a slow fire growth rate.

NOTE 3 Areas of high fire risk (see 13.4) are generally allocated at least fire growth rate category 3 (see Table 3). However, if an enclosure or compartment that contains a localized area of high fire risk (such as a cooking range within a catering area) is provided with an effective localized suppression system (see Clause 38), then the overall risk profile can be treated as medium risk rather than high risk.

Table 3 Fire growth rates

Category	Fire growth rate A)	Fire growth parameter B)	Description	Typical examples c)
1	Slow	0.003	Evenly distributed low level fire load, small discrete packets of fuel or material of limited combustibility D)	Reception areas, concourses (without concession outlets) and halls with limited fire load such as sports stadia and foyers
2	Medium	0.012	Evenly distributed low to mid-level fire load comprising a mix of combustible materials	Offices, lounges, classrooms, auditoria, seating areas, galleries and car parks E)
3	Fast	0.047	Stacked combustibles (on or off racking and shelving but excluding high rack storage), some small quantities of materials other than materials of limited combustibility D) (or where larger quantities are stored in separate fire-resisting enclosures), process, manufacturing or storage of combustible materials	Shop sales areas F), workshops, factories and small storage buildings
4 G)	Ultra-fast	0.188	Medium to large quantities of materials other than materials of limited combustibility D), high racked storage, flammable liquids and gases or where rapid uncontrolled fire growth could occur	Warehousing H), processing plants and car parks E) utilizing a car stacker or similar method where there is no fire separation between stacked cars

a) These categories are related to the fire growth rate and not the ultimate potential fire size.

b) This is discussed in PD 7974-1.

c) These are examples only and may be varied according to the specifics of the building/room contents.

d) Limited combustibility is defined in 3.77 and includes for this purpose materials also defined in 3.85 as non-combustible.

e) Includes both open and non-open sided car parks.

f) Includes covered shopping complexes and department stores as well as high street shops and premises for personal services, delivery and collection of goods for cleaning/repair/treatment either carried out by staff or by members of the public themselves. Combustibility, quantity and how goods are displayed should also be taken into account and the risk category amended accordingly.

g) See Table 4. This category is unacceptable unless a sprinkler system is installed.

h) This is a worst-case assumption. Combustibility, quantity and the way in which goods (including packaging) are stored should be taken into account and the risk category amended accordingly

6.4 Creating the risk profile

a) Risk Profiles: Defined by a combination of occupancy characteristics and fire growth rates.

b) Diverse Risk Profiles: Buildings often do not have a uniform risk profile throughout.

c) Ancillary Accommodation: May have different fire growth rates or occupant profiles compared to the main areas.

d) Mixed-Use Buildings: Likely to contain a variety of occupancy types, each with distinct risk profiles

Table 4 Risk profiles

Occupancy characteristic (from Table 2)	Fire Growth rate (from Table 3)	Risk profile
A (Occupants who are awake and familiar with the building)	1 slow 2 Medium 3 Fast 4 Ultra-fast	A1 A2 A3 A4 A)
B(Occupants who are awake and unfamiliar with the building)	1 slow 2 Medium 3 Fast 4 Ultra-fast	B1 B2 B3 B4 A)
C (Occupants who are likely to be asleep)	1 slow 2 Medium 3 Fast 4 Ultra-fast	C1B) C2 B) C3 B), C) C4 A), B)

A) These categories are unacceptable within the scope of BS 9999. Addition of an effective localized suppression system or sprinklers will reduce the fire growth rate and consequently change the category (see 6.5).

B) Risk profile C has sub-categories (see Table 2). Risk profile C3 is unacceptable under many circumstances unless special precautions are taken.

C) Risk profile C3 is unacceptable under many circumstances unless special precautions are taken.

● Assessment Required: Evaluate the reliance of each occupancy type on prescribed fire precautions within a building or floor.

● Common Measures: If different risk profiles depend on a shared measure (e.g., fire resistance), use the most conservative risk profile to determine the minimum requirement.

NOTE 1 If there is no reliance on a common measure, the risk profile giving the most conservative limits does not necessarily have to be applied throughout the entire building.

6.5 Variation of risk profile

a) Automatic Sprinkler Systems: Control fire by restricting growth, preventing spread, limiting heat and smoke, and potentially extinguishing the fire.

b) Fire Growth Rate Reduction: Installation of sprinklers can lower the fire growth rate by one level, but only in sprinkler-covered areas.

c) Sprinkler Coverage: Sprinklers must cover corridors and linking spaces or be separated from these by fire-resistant construction.

d) Risk Profile Reduction: Sprinkler systems can reduce risk profiles (e.g., B3 to B2, A2 to A1).

e) Design Standards: Sprinklers must comply with BS EN 12845, BS 5306-2, or BS 9251 for risk profile adjustment. Water mist systems can be an alternative if designed per BS 8489-1.

Example Adjustments:

● An un sprinklered B3 shop becomes B2 with sprinklers.

● An un sprinklered A2 office becomes A1 with sprinklers.

● Sprinklers can reduce an unacceptable B4 profile to B3.

NOTE There are limitations on the use of water mist as set out in BS 8489-1.

6 Risk profiles