Download pdf - BRE FIRE CONFERENCE 2015 Research Conference 2015/4...BRE Fire Conference 2015 11th June 2015 Tom Lennon Fire Safety Team, BRE Global Compartment sizes -Background –As part of a

Part of the BRE Trust

BRE FIRE CONFERENCE 2015

11th June 2015

Part of the BRE Trust

Compartment sizes – are they still fit for purpose?

BRE Fire Conference 201511th June 2015

Tom LennonFire Safety Team, BRE Global

Compartment sizes - Background

– As part of a recent DCLG project dealing with Compartment sizes, resistance to fire and fire safety BRE Global have undertaken research into a number of linked work streams dealing with fire safety and the associated provisions in Schedule 1 of Part B of the building regulations 2010.

– This presentation concerns Maximum fire compartment sizes. The aim of this work stream was to produce robust evidence and data to explore the potential to develop a systematic method for determining maximum compartment sizes based principally on life risk, but taking into account other factors such as environmental impact.

Maximum fire compartment sizes - Background

– This project has explored the potential to develop a systematic method for determining maximum compartment sizes based principally on life risk

– Compartmentation is used to sub-divide buildings so as to restrict fire size and minimise fire spread. For non-domestic buildings AD B (Volume 2) sets out maximum compartment sizes dependent on the height and use of the building. There are different values for certain categories dependent on whether sprinklers are installed or not

– There is currently no recognised engineering method for establishing the appropriate maximum compartment size for a particular building

Current situation

– Guidance to the building regulations (Approved Document B, Fire safety, B3 Table 12) provides limitations on the maximum size of compartments

– For single-storey buildings there is no limit on the maximum size of compartment in the industrial category. Note this category would include large single -storey portal frames with a height to the eaves up to 18m.

– Requirements from the insurance industry restrict the maximum floor area in industrial buildings to 7000m² in the absence of an approved automatic sprinkler system

Maximum compartment sizes

Tasks– Review of background to existing AD B requirements

– The maximum dimensions of buildings or compartments in Table 12 of AD B are based in large part on survey data from the 1940s. The background information has been reviewed and recommendations made as to areas where the existing requirements would benefit from a reappraisal.

– Review of existing fires database– Existing published information has been reviewed to identify the relationship between

compartment size and impact. Any trends relating to the impact of modern forms of construction on fire size and severity has been highlighted

– Review of alternative approaches used to derive maximum compartment size– An international review of standards, guidance and accepted practice has been undertaken.

Review of background to existing AD B requirements

– Current provisions based on Post-War Building Studies No. 20 Fire Grading of Buildings

– Original restrictions in relation to maximum floor areas and maximum cubic capacities dependent on nature of construction and nature of fire hazard

– Recommendations a balance between limiting potential losses and imposing barriers to trade

– Original bye laws only applied to buildings incorporating combustible materials

– Subsequent changes to the guidance have removed the distinction between combustible and non-combustible materials with performance based functional requirements applied to all forms of construction


– Principal factors that influence the regulations governing the maximum size of fire compartments are:– The type of construction– The nature of the occupancy– The location and particularly the proximity of other

buildings and– The nature of fire precautions including the

provision of an automatic sprinkler system


– Currently no limitation on compartment floor area for single storey industrial buildings

– Original recommendations proposed a similar approach for single storey buildings of Construction Type 1,2 or 3 (protected or partially protected) for low fire load occupancies but did impose restrictions in relation to other types of construction or higher fire loads

– Where restrictions are imposed (e.g. multi-storey industrial building) the compartment floor area can be doubled if a suitable sprinkler system is installed. This is in line with the recommendations of the post-war building studies report for incorporating the benefits of a suitable suppression system.


– Very large single storey industrial and storage buildings have been constructed in recent years on green field sites where there are no issues around adjacent structures and no access problems for the FRS

– In such cases structural elements only supporting a roof do not require any specific level of fire resistance

– Although the current regulatory guidance does not specify any limitation in maximum compartment size for such buildings insurance industry requirements may limit compartment size


– Property protection requirements limit the maximum compartment size in single storey industrial buildings to 7000m² and 14000m² where an automatic sprinkler system is installed

– This is in line with the AD B guidance for mult-storey industrial buildings up to 18m high

– The study has failed to find any scientific basis for the sprinkler factor

Review of existing fire database and compartment sizes

Table 1 – Number of buildings of different sizes, in different occupancy classes

Description

Total area (m2)

< 2,0002,000 to

4,9995,000 to

9,99910,000 to

20,000 > 20,000 Unknown Total

Factories Workshops and Warehouses (Including Bakeries and Dairies) 296,100 16,750 5,180 1,840 70 230 320,170Factory Shops 1,320 0 0 0 0 0 1,330Food Processing Centres 140 20 20 10 0 0 200Food Stores 510 0 0 0 0 0 520High Tech Warehouses 20 0 0 0 0 0 20Large Distribution Warehouses 20 50 160 370 510 0 1,120Large Food Stores (750 – 2500 m2) 1,970 220 0 0 0 0 2,190Large Industrials (Over 20 000 m2) 0 10 30 160 790 30 1,010Large Shops (750 - 1850m2) 400 10 0 0 0 0 410Large Shops (Over 1850m2) 190 1,300 320 100 20 0 1,940Refuse Destructor Plants/Disposal Sites 0 0 0 0 0 0 0Retail Warehouses and Food Stores 6,190 1,450 180 100 10 10 7,930Shops 406,380 110 0 0 0 260 406,760Storage Depots 1,650 280 80 20 10 10 2,050Stores 68,920 290 50 20 0 60 69,340Waste Incinerator Plants 0 0 0 0 0 30 30Waste Recycling Plants 0 10 0 0 0 120 130Waste Transfer Stations 0 0 0 0 0 620 630Wholesale Warehouses 240 90 80 40 0 0 450Cold Stores (Rental Valuation) 120 80 50 50 20 10 330Warehouses Within/Part of Specialist Property 100 10 0 0 0 0 110Workshops Within/Part of Specialist Property 130 10 0 0 0 0 130



Afire = 2.79 Aroom0.69




p(Afire) QAfire-0.2



p(Afire) QAfire-1



Equivalent fatalities:

• Each actual fatality = 1 equivalent fatality

• Each severe injury = 0.1 equivalent fatality

• Each slight injury = 0.01 equivalent fatality

• Each injury treated by first aid = 0.003 equivalent fatality

• Each recommended precautionary check = 0.001 equivalent fatality

• Each person rescued (uninjured) = 0.001 equivalent fatality

• Each unspecified injury = 0.0003 equivalent fatality.





Conclusions from fire statistics

• Clear trend for average fire area to increase as area of room of origin increases

• No obvious trend for life risk to increase as area of room of origin increases

• Sprinklers reduce the life risk in non-residential buildings

• In dwellings and other residential buildings, statistics are too sparse to draw any meaningful conclusions directly from the data

• Primary benefit of sprinklers in non-residential buildings is property protection (since life risks are low anyway)

Review of alternative approaches used to derive maximum compartment sizes– A review has been undertaken based on information

supplied by Arup Fire of alternative approaches to deriving maximum compartment sizes to provide an international perspective in relation to regulatory requirements

– The review has focused specifically on the issue of maximum compartment sizes for single storey industrial and storage buildings (excluding car parks)

– The provisions within the regulatory guidance in relation to maximum compartment sizes for England and Wales are the least onerous of all the countries investigated

Review of alternative approaches used to derive maximum compartment sizes– The results from the review show a great deal of

variation with regard to limitations on compartment size

– Restrictions on compartment size vary according to occupancy type

– Recognition in some countries that a simple occupancy based classification is too simplistic and too crude. Further broken down by nature of the fire load or risk category associated with the activity

– The USA situation differs from all overs covered for two reasons. Firstly design may be undertaken to any one of a number of National or State codes. Secondly requirements are related not only to the type of occupancy but also to the nature of the construction type.

Review of alternative approaches used to derive maximum compartment sizes– Because of the different classification the USA was not

included in the comparative study

– Information was also provided for France and Germany. However, the regulatory system in these countries does not lend itself to the simple comparative approach adopted in the review.

– The results from the study are summarised in the Table that follows

Country Code/Guidance/Regulation Single-storey industrial Single-storey storage

Unsprinklered Sprinklered Unsprinklered Sprinklered

High risk Low risk High risk Low risk High risk

Low risk

High risk

Low risk

England AD B No limit No limit No limit No limit 20000 20000 No limit No limit

England AD B (property protection) 7000 7000 14000 14000 2000 8000 2000 8000

Wales AD B (Wales) No limit No limit No limit No limit 20000 20000 No limit No limit

Scotland NDTGD 33000 93000 66000 186000 1000 14000 2000 28000

ROI TGDB 33000 93000 66000 186000 14000 No limit 28000 No limit

Australia BCA 2000 2000 2000 2000 2000 2000 2000 2000

Hong Kong HKCPSFB 10500 10500 10500 10500 10500 10500 10500 10500

South Africa SANS 10400 5000 5000 No limit No limit No limit No limit No limit No limit

Greece Fire Building Regulation PD 71/88

5000 20000 12500 4000 3000 3000 3000 3000

China GB 50016-2006 2500 2500 5000 5000 2500 2500 5000 5000

Holland DBR 2500 2500 No limit No limit 1000 1000 No limit No limit

India NBCI 1125 1125 No limit No limit 1125 1125 No limit No limit

Denmark Information on fire safety sizing 2000 5000 10000 10000 2000 5000 10000 10000

Overall conclusions

– The aim of this work stream was to produce robust evidence and data to explore the potential to develop a systematic method for determining maximum compartment sizes based principally on life risk, but taking into account other factors such as environmental impact.

– The review of statistical data has shown no clear correlation between compartment size and life safety for compartments with floor areas larger than 500m² for large single-storey industrial and storage buildings

– The review of international requirements in relation to maximum compartment floor area for single-storey industrial and storage buildings found no systematic method for determining maximum compartment sizes based principally on risk