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Theme: fire

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Rigid adherence to guidance on designing for fire has saddled the UK with constricted apartment buildings. But by thinking imaginatively we could achieve the kind of spaciousness typical of American flats while reducing the risk to occupants In the 19th century, Britain needed low-rise, functional, cheap terrace accommodation to house workers in the rapidly growing towns and cities. Since then it has undergone a number of cultural and social revolutions, but despite this progress one question remains: why is our residential accommodation so dull?

Even in grandiose residential apartment buildings we still expect people to enter via dingy hallways and cramped entrance halls into small segregated apartments. Any enlightened design team trying to break free of this design is stopped by the Building Regulations on the grounds of life safety.

Fair enough - we have a duty to design safe places to live. But if any departure is so dangerous, how do the Americans manage to design open-plan and spacious apartments? Can we design apartments the same way? Or is the United States, as a consequence, a more dangerous place to live?

In 2000, US fire departments recorded 4,045 fire deaths across the US, with 3,420 deaths occurring in residential dwellings.

1The UK, on the other hand, recorded a total of 663 fire deaths (in 1999), of which 466 occurred in residential accommodation.

2Ifreviewed in relation to the population, the US has a death rate of approximately 13.1 fire deaths per million compared with the UK's 11.1 fire deaths per million.

3This difference of two deaths per million population encompasses all residential accommodation, including trailers etc, and not solely apartment buildings. It relates to a variety of factors based on the lower density of the US. These are more a reflection of fire service response times (there are greater distances between fire stations and residential dwellings, especially in remote areas) than of the escape provisions of apartment buildings.

Cultural differences In the UK, all residential buildings are required to comply with the functional requirements of the Building Regulations, usually by applying the recommendations of Approved Document B (AD-B) or other relevant guidance documents (eg BS 5588 Part 1).

4Other methods of complying with the regulations are acceptable, although they place the burden of proof on the design team and, as a result, are rarely used.

In comparison, the US has various model codes, including the International Building Code (IBC), the National Building Code (NBC), the Standard Building Code (SBC), the Uniform Building Code (UBC), and the National Fire Protection Association (NFPA) life safety code. To complicate things further, each state has its own building legislation. This is based on one (although sometimes more) of the standard models and can have subtle local differences.

Despite some differences in the evacuation of the occupants of residential apartments, it is possible to compare the internal layouts of UK and US residential designs by looking at the NFPA life-safety code and the requirements of AD-B.

5In the UK there are three different internal flat layouts recommended by AD-B.

These are:

lProtected entrance-hall approach - all habitable rooms (not the kitchen and bathrooms) should be accessed via a 30-minute fire-rated protected corridor. The maximum travel distance from the door of each habitable room to the flat entrance door along this protected corridor should be no greater than 9m. There are no limitations on the size or distance in each of the habitable rooms.

lOpen-plan design - the flat should have a travel distance of no more than 9m from the furthest point in the flat to the entrance door. This is normally only used in 'studio flats' or 'crash pads'.

lAlternative means of escape - the kitchen and living accommodation should be separated from the bedrooms by a 30 minute wall. Two means of escape should be provided from the apartment, one from the bedroom portion and the other from the living room/kitchen.

For all these flat types the use of inner rooms (except kitchens and bathrooms) is prohibited and limited smoke detection is required. The smoke-detection requirements vary between different flat designs but usually consist of a single detector and alarm in the entrance hall.

The NFPA life-safety code places the emphasis on the provision of active protection systems, which determine the restrictions on the internal layout of the apartment. Almost all new apartment buildings are required under the NFPA code to have a residential sprinkler system, although some small building types are exempt.

Several different types of sprinkler heads are available to designers in order to minimise the impact on the layout or construction of the apartment. These types are split into sidewall (or horizontal) sprinklers and ceiling-mounted (vertical sprinkler heads). Both types of heads are available to suit any room dimension or situation. Among common vertical or ceiling-mounted heads are the:

lFlat plate. This is attached by fusible links and drops off revealing the sprinkler head.

For example, the Tyco series LFII 'concealed' pendant, the Reliable Model G4A, aka 'The Concealer', and the Viking 'Mirage'.

lFlush pendant. In this design the head hangs below the ceiling in a small, concealed protrusion. For example, the Tyco series LFII 'Flush' pendant.

lUnconcealed heads. These heads have the fusible link or bulb open to the room rather than hidden behind a plate. Similar to sprinkler systems installed in office or industrial buildings, these are rarely specified in residential apartments. Product types include the Tyco series LFII pendant sprinkler or the Angus Thermomatic S-QR quick-response pendant from Kidde Fire Protection Services.

Horizontal heads (also known as sidewall sprinklers) are less common in residential apartments than vertical heads. They are, however, often specified in hotel, hostel or student accommodation. Both concealed and recessed head types are provided and include the Viking VK440 (Model M-4) Residential Horizontal Sidewall Sprinkler.

The NFPA life-safety code states that where a sprinkler system is provided the limitations on the apartment layout are:

lThe travel distance from the furthest portion of the flat to the flat entrance door shall not exceed 38m.

lSmoke alarms should be installed outside every sleeping area in the immediate vicinity of the bedrooms. These would typically comprise detectors powered directly from the mains supply, with typical examples including the ADT Minerva smoke detector, Chubb Fireseeker ZA or Apollo Series 60 optical detector.

lThe means-of-escape route for the apartment should not pass through any room that may be locked (for example a bathroom).

The provision of sprinklers to residential apartments therefore allows a much greater flexibility than exists in UK. So why don't we adopt the same approach?

Home economics Sprinkler systems suffer from a negative press in the UK due to designers', developers' and occupiers' concern about high costs of installation, loss of aesthetics within the apartment and the possibility of water damage to resident's property both in the flat of fire origin and in adjacent dwellings. So why do US developers and designers provide sprinkler systems?

Residential sprinklers designed to the standard given in NFPA 13 or the UK draft code of practice DD251 are estimated as being equivalent to approximately 1-2 per cent of the total cost of constructing the apartment. This is usually equivalent to providing the carpet or several of the white goods in the kitchen. The average cost from previous projects has usually worked out as approximately £1,000 per apartment or £22/m 2. This can be reduced for larger apartment blocks through economy of scale.

This is an almost negligible cost implication in the design of a high-specification residential apartment and could be offset against a higher purchase price. The Residential Sprinkler Association (UK) estimates that property damage for a residential apartment is reduced by about 80 per cent when a sprinkler system is provided - surely a good selling feature for the occupants?

So perhaps aesthetics is the problem?

Wrong. The technology behind residential sprinkler heads is improving every year, with the latest developments being in the creation of recessed or concealed heads (such as the Central Spraysafe LFII concealed pendants installed by Homesafe).

How about the risk of water damage?

Sprinkler heads are usually activated by a fusible link or glass bulb rated at 68infinityC. This is unlikely to be activated by any heat source other than a fire. In fact, the sprinkler community rates the chances of accidental discharge for any sprinkler systems as one in 16 million. Accidents are further minimised in residential systems by provision of a cover plate to the sprinkler. This both assists the aesthetics and prevents the bulb from being broken by even the most accurate missile a child (or adult) can hurl.

Leakage from the heads or pipework is estimated by the sprinkler companies as equal to or even less than that from any other water system provided in the house (such as a central heating system). This is not surprising considering the thousands of installations undertaken in areas where hygiene is of prime consideration, such as foodpreparation areas and hospitals.

Even in an actual fire, the water damage caused by a residential sprinkler, which delivers water at 10 to 15 litres per minute, similar to a good power shower, is nothing compared with the 250-500 litres per minute delivered by a single fire-service hose.

So sprinklers have a low cost impact, minimal effect on the look of the apartment and a negligible chance of causing accidental water damage. US developers and designers provide residential sprinkler systems in their prestige apartments - the small cost implication is more than offset by greater design flexibility (and higher selling prices).

Consider the litigious nature of American society; if there were problems with sprinkler systems, would US developers have been installing them for decades?

Fire proof In 1998, Vancouver, a city of almost 550,000 inhabitants, did not have a single fire death.

This is accredited by fire chief Ray Holdgate to the 1990 bylaw requiring all new residential construction to be provided with sprinklers.

6By 1999, this accounted for almost 38 per cent of all multi-residential units.

Under the Building Regulations, the emphasis is on proving the proposed design meets the functional requirements of the Building Regulations. Given the widespread use of sprinklers in US residential buildings and their excellent life-safety record, early discussion with the Building Control Authority could prove beneficial.

Alternative approaches The design team isn't limited solely to the provision of sprinklers in residential apartments in order to depart from the guidance of Approved Document B. Another alternative is to provide an enhanced fire-alarm and detection system in the apartments.

AD-B guidance requires a simple detection system, usually in a protected entrance hall, which alerts the occupants in the event of smoke leakage into the escape route. This enables occupants to start evacuation before the corridor becomes completely smoke-logged.

This is logical when a small protected entrance hall is provided, but what happens if you wish to depart from this design?

Heat and smoke detectors have an important role to play in expanding the way UK designers view residential apartments. By providing smoke/ heat detectors in every habitable room of the apartment, it is possible to alert the occupants the moment a fire is detected (about 60 seconds after ignition). This gives them more time to evacuate before conditions in the flat become untenable.

Aesthetically, the latest smoke detectors have a flatter, less obtrusive design.

Products such as the Apollo XP95 optical detector or the ADT Minerva M600 and M900 range of smoke detectors are suitable for all habitable areas of the apartment.

Heat detectors are valuable at detecting kitchen fires - the most common domestic fires.

The detectors activate only when the corresponding temperature rises faster than expected, as would happen in a fire but not from kitchen fumes.

Detector types include the Apollo Series 60, Tyco H series or the Chubb ZA rate-ofrise detectors.

Alternatively, multi-sensor detectors can be used that combine heat and smoke detection. Apollo's XP95 multi-sensor detector contains an optical smoke sensor and a thermistor temperature sensor whose outputs are combined in order to detect the fire (preventing cold smoke produced by burning toast activating the detector). These are useful in combined kitchen and living rooms.

Fire statistics gathered by the Fire Service (and other relevant parties) for the Home Office for 1999 indicate that 84 per cent of all residential fire deaths occurred in domestic dwellings not provided with smoke detection or where the detector failed to operate.

This is equivalent to 392 fire deaths out of the total of 466 fire deaths occurring in residential apartments.

Seventy-one per cent of all fires in residential dwellings were detected within five minutes, yet in only 53 per cent of fires in dwellings not provided with smoke detection was the fire detected in a similar time period. The installation of hard-wired smoke detectors, positioned accurately, could therefore reduce the number of fire deaths by decreasing the time to detection substantially. Detectors save lives. Increased research and development will limit their physical intrusion into the apartment space, reduce false alarms and provide even earlier warnings.

One of these new developments is the use of carbon monoxide (CO) detection as either a stand-alone detector or as a combination smoke and CO detector. CO is a toxic combustion product that is usually only formed during fires (or from faulty heating appliances) and not from burnt toast, therefore reducing false alarms.

An example of a stand-alone CO detector is the Tyco MU601 CO detector, although many companies are currently researching combination detectors, such as the Tyco MX 800CH heat and CO detector, for use in the domestic market.

Depending on the apartment design, simply providing detection may not be enough to satisfy the functional requirements of the Building Regulations.

However, computer modelling can determine the behaviour of fire and smoke in a residential apartment. This, combined with an assessment of the likely pre-movement and response times of residential occupants, can determine if untenable conditions will result in the apartment prior to the occupants' escape.

Time for change?

As designers, are we allowing our traditional views on the provision of life safety systems in our 'castles' to get in the way of new designs? Building Regulations only apply a functional requirement. So why do we design residential apartments to the limitations given in AD-B? Why don't we design large open-plan flats?

Given the life-safety benefits of residential sprinkler systems and the high reliability of the systems, demonstrated by 100 years of installation, why don't we put them in more residential buildings?

Additional detection could be provided in the building. Proven benefits of detection in real fire scenarios could justify departures from the Approved Document for issues such as the provision of extended travel distances or inner rooms.

Finally, the use of computer modelling has reached a stage where an accurate assessment of the behaviour of the fire and smoke in a residential apartment can be obtained quickly and easily.

Miller Hannah is principal of Hoare Lea Fire;

Gary Daniels is a fire engineer with Hoare Lea; Kevin Leahy is regional director in London for Broadway Malyan; Terry Watson is technical director of GEM Consultants References 1 Karter, MJ, Fire loss in the United States during 2000. National Fire Protection Association.

September 2001.

2Watson, L, Gamble, J, Schofield, R, Fire Statistics United Kingdom 1999. Issue 20/00. Office of the Deputy Prime Minster. November 2000.

3 Hall, JR, Fire in the USA and the United Kingdom. National Fire Protection Association.

December 2000.

4 Approved Document B to the Building Regulations. HMSO. 1991 (2000 edition).

5 Cote, R, (ed), NFPA 101: Life Safety Code.

National Fire Protection Association. 2000.

6Holdgate, R, 'Mandate for sprinklers'. Fire Prevention - Fire Engineers Journal.

September 2001.

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