STABILISATION, CONTROL and CONTAINMENT
   
 
HIGH-RISE Fire Fighting
  Developing better responses to fires in tower bocks and high-rise buildings.
     
 

 

Stabilisation

Stabilisation should be viewed as a measure or measurese specifically designed to prevent any forseeable escallation of the incident. Stabilisation would normally be thought of as a requirement BEFORE any attempt at active firefighting or compartment entry, but it may be required or occure at any stage. Stabilisation can take the form of simple measures carried out by occupants even before the arrival of the FRS. Closing doors as they evacuate will reinforce compartmentation, Installation of fire suppression systems will inhibit fire developement.

First attending crews must be mindfull that there initial actions could de-stabalise any incident

 

 

Identifying and Controlling the risk areas

 

ZONING: The UK FRS Document on Incident command details a command layout for High-rise buildings. This model is used to define a system of vertical sectorisation.  Most UK FRS will uses this model as preferred or best practice.  Later in this article we will analyse and review how efficient it is in real life scenarios.


Initially, we need to concentrate on THE RISK AREAS. Areas where fire-fighters, other Emergency responders or the public may be located and the potential risks (and required control measures) identified. The Risk Areas may be designated by an easily identified name. Numbers would be unsuitable as this may cause confusion with floor numbering.
The designation of these areas should tie in this the safety requirements of those persons in that area.
Some typical Risk Zoning systems are detailed:


Typically a system of High, Medium and Low risk may be identified.


High Risk. Areas requiring Fire-fighters to be in full PPE using RPE ( SCBA ) with a protective main hose line. These areas should be immediately evacuation of all members of the public. This is a no-go area for all other Emergency responders.


Medium Risk. Areas requiring fire-fighters to be wearing full PPE and to have immediate access to RPE (worn but not in use). Fire-fighters in this area must be supervised by a suitably protected command qualified officer who has communications with the IC and Bridgehead commander and who can instigate an evacuation if required. Members of the public will be advised to immediately leave this area. Other Emergency responders will only work in this area after a briefing and under direct supervision of the FRS. Their presence and location must be recorded and logged


Low risk: Fire-fighters levels of PPE may be reduced at the command of the Sector commander. Members of the public may be asked to leave the building or to “stay put and remain in there flats awaiting further instruction”. Other Emergency responders may work in this area, but their presence and location must be recorded and logged
Implementation: At the boundaries of each risk area, safety observers should be posted as soon as possible to watch for determination and/ or spread.  An external Safety observer should be in place at all High rise incidents as a priority.


It would be advantageous for the potential for spread to be anticipated and built into the risk area designation.  For example a fire may be confined to a single flat behind a fire door. But the moment that door is opened, typically by crews entering to extinguish the fire, smoke would reasonably be expected to contaminate the corridor. Also vertical spread is becoming a more common phenomenon in high rise fires and it may be that flats directly above or below may be designated at an elevated risk.
With the known and extensive spread observed at the Lakanal House fire, it is more difficult for IC to safely anticipate fire spread.  Floor to floor spread by internal means (breeches in compartments ion) or external means (Coander effect and falling debris)

 

 

Containment

Definition:
In relation to high rise fire fighting, containment is keeping the fire under control. To understand how a containment may work you first need to understand the physics of how fire spreads.

Heat (Energy) from a fire will spread in three ways CONDUCTION, CONVECTION and RADIATION

Containment can be internal or external, direct or indirect and can relate to both fire and smoke control. It can be used in conjunction with and in parallel to other High rise tactics.

A form of Containment is usually in place long before the FRS is called. The existing compartmentation (fire resisting) that is a feature of virtually all High rise buildings is designed to contain a fire. Containment tactice must always be viewed in conjunction with how compartmentation may assist FRS crews.


There can be an overlap between what is assumed to be containment and Intervention. Containment can be viewed as actions external to the fire compartment. These may include covering jets, automatic suppression systems (fixed installations), fan sprays, ventilation & pressurisation systems, PPV, fog injection (Cold cut).  Some of these may well fully extinguish the fire but they are normally deployed as ‘containment’ tactics, pending a compartment intervention.


Function:
Containment tactics can help in any one, or a combination of:

  • Evacuation: Containment will slow or stop the escalation of an incident allowing more time for evacuation or lessening the numbers of people required to evacuate.
  • Damage control: Effective containment will restrict the incident size. Thus lessening damage to the remainder of the building.
  • Intervention: Mitigate any Intervention: Containment will slow or stop the fire growth, ultimately lessen the size of the incident and may in fact lead to a significantly smaller intervention as a contained fire reaches a decay phase (burn out)
  • Time: Containment will allow further resources (including specialist equipment) to be put in place before a compartment intervention is attempted.
  • Resourcing: Successful containment may lighten the resource requirements.

 

Containment is an acknowledged tactic for many incident types.  Covering jets (to mitigate spread) have been deployed by default at all Internall fires for many years. In ship fire fighting, boundary cooling and fan sprays are a standard tactic. In high rise there has been a traditional focus on getting into the compartment as soon as possible. But if you review the design of most high rise flats, they are designed with fire resisting compartmentation as a primary goal. Could FRS use this compartmentation better?

 

Fixed installations (sprinklers):
Sprinklers are primarily designed to detect and suppress a fire ate the earliest stage possible. Many are activated at a specific temperature ( usually 68 deg C). More modern systems rely on an electronic detection system to activate the sprinkler and sound an alarm. Conventional sprinkler systems are usually found in commercial and retail buildings. Domestic dwelling sprinklers are starting to appear in high rise flats. These are often high pressure mist systems and may have limited water  supply.


Covering Jets:
Often the problem with covering jets is positioning so they may be effective. Externally a good jet from ground level may reach 4-5 stories. A smooth bore branch may reach the 6th floor. Ground monitors should reach the 6th or maybe the 7th floor.  These jets are pointing upwards to obtain height and as such have limited penetration into any compartment. They will however assist in controlling external spread and can be effective in dealing with falling burning debris.  With some building layouts, jets may be deployed through windows of unaffected flats that look onto the incident compartment.
Corridor covering jets may be put in place, but these must be manned by crews in full PPE and BA. Spraying water onto a wooden flat door will have little effect (due to its inherently low thermal conductivity). Spraying water onto doors with glass panels may cause a sudden unexpected failure. UPVC doors, although not flammable, will degrade and decompose under heat. They may lose their structural rigidity, often resulting in insert panels falling out. If for any reason it is thought prudent to spray water onto a flat door, consider using a fan spray (if available) or an improvised branch holder so that crews may withdraw from the directly affected area. When using any internal containment tactic crews should be in BA and they must always be mindful of their means of egress. If there is any possibility of incident escalation affecting them they should withdraw immediately.


External Monitors (ALP/TL)
Height vehicles will allow better positioning of external jets provided there is good external access to the building. Many high rises only offer height vehicle access on one or two faces of the building.
Hand held jet can be deployed from height vehicle cages extending their reach to potentially the 13th floor. Many height vehicles have the own monitors and fixed pipework. These may be capable of delivering large quantities of water to the 18th or 19th. Recent tests (2011) of a Bronto F32 ALP with  2600 l/m monitor projected water to heights exceeding 60m ( effectively 20 floors).  A priority consideration is securing a large and sustainable water supply from a dedicated base pump. Care must be taken not take water from any internal crews who are involved in internal fire fighting. Elevated sprays can control external spread and jets directed into the fire compartments may have a very beneficial effect on the main fire. If the compartment windows (or balcony doors) are intact then great care should be talked with external water application. This may cause premature failure and  result in a fast escalation ( wind driven, fully ventilated fire). Of course external ventilation may be desirable to reduce the risk of a backdraft or to release heat and products of combustion from the compartment.


 

Fixed ventilation and pressurisation systems:
There are two functions of these systems within high rise buildings. One is the day to day air management in the building (this includes HVAC ) and the second is smoke control during a fire.
At its simplest many High rise buildings have Automatic opening vents (AOV) that activate upon the detection of heat or smoke. Building regulations have required AOV in corridors and at the head of stairwells. Their purpose is to dilute smoke in escape routes to allow occupants to leave the building. They are not to facilitate the FRS but they may keep areas relatively smoke free to allow fire fighters to reconnaissance or evacuate effected areas.  Most AOV will open and stay open with no facility to automatically or remotely close them. This may lead to the creation of undesirable air tracts that unduly ventilate a fire or that may allow external wind pressure to push smoke around the building.
More advance systems will include HVAC and full air conditioning systems and these should have smoke monitoring and dampening (intumescent) built in. 
Dedicated ‘fire’ air handling systems are primarily pressurisation systems. They are not designed to handle air at an elevated temperature. but to dilute or exclude products of combustion from communal areas using pressurisation.  These systems also operate to assist in the initial evacuation of communal areas, but also, they may be designed to assist Fire fighters by maintaining tenable conditions prior to intervention. 


Positive Pressure Ventilation (PPV)
PPV can be used in two ways by the FRS:
Pressurise a specific area. Usually a stairwell or corridor to maintain an evacuation route or means of egress for fire fighters. The pressurised area should remain free from smoke and products of combustion. This may be a very effective use of PPV in the earliest stages of an incident.
Create airflow, drawing smoke and products of combustion to an outlet point. As with all PPV usage any outlet point will need close monitoring and may even need a covering jet. Because of this it is not envisaged that using PPV to create airflow would be instigated in any area that may affect airflow in areas directly affected by fire.
With all PPV deployments in High rise buildings the higher wind speeds associated with these designs must be considered. Wind pressure may over-run the pressurisation that PPV is capable of generating.


Fog (mist) injection systems (variously known as Nimbus, Cold-cut, Cobra)
A recent innovation in active fire suppression is the use of fog or Mist injection systems. They work by cutting small diameter holes through the structure of the compartment (this can include concrete, wood, steel and brick) using an aggregate. This aggregate is propelled in a very high pressure water stream, usually around 300 bar. The effect is similar to shot blasting.  Once the hole is complete the aggregate can be switched off and the high pressure water (which is atomised) is projected into the compartment. As these systems start to be introduced to UK FRS, suitable Standard  Operating Procedures (SOP) will be developed for high rise buildings. (see Note)

 


 

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