CPD: Fire prevention on construction sites
Continuing Professional DevelopmentFire prevention on construction sites: January 2011
• Working with acetylene
• The dangers of working on high-rise buildings
• Timber-frame construction
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Burning issues to avoid catastrophic site fires
Adair Lewis, technical manager of the Fire Protection Association, outlines key changes to the updated Joint Code of Practice for Fire Prevention on Construction Sites
Health and safety records show that construction sites are dangerous places, with death and injury only a step away. On the face of it, the Fire Statistics Monitor, published by the UK Statistics Authority, seem to show that construction sites are not such a serious problem, accounting for only 0.2% of all fires every year. However, fires in buildings that are being built or refurbished are often disproportionately large, in terms of the magnitude of the fire and the cost of the property damage.
In a recent 10-year period, statistics from insurance companies show that there were 108 major fires on construction sites, costing the insurers — and therefore construction companies via their premiums — £187.3m, an average loss of £1.7m. In the same period, accidents while carrying out hot works caused 164 major fires, resulting in total losses of £69.8m. Of course, the costs of lost employment, damage to nearby businesses and homes, loss of our heritage and contamination to our environment adds to the overall cost.
Construction sites are full of hazards that present the potential for accidental fires to start. But it is not just site-related events that lead to fires — arson is a major problem. It’s thought that as many as 55% of the fires that occur on sites are the result of arson.
At the end of the 1980s, the problem was even worse, with the number and cost of fires in the construction industry reaching a level where insurers were questioning whether the provision of insurance for construction sites could economically continue. Either the premiums had to increase to an unacceptable level, or the industry had to get its house in order.
As a result, in 1992 the Fire Protection Association and the Building Employers Confederation (which later became the Construction Confederation, and is now the Contractors’ Legal Group), along with the support of other bodies, including the Association of British Insurers (ABI), London Fire Brigade and the Chief Fire Officers Association, published the first edition of the Joint Code of Practice for Fire Prevention on Construction Sites. Since then, the code has been developed and expanded and now, with the publication of the 7th edition in 2009, it has the full support of the industry.
The Joint Code of Practice sits next to the HSE publication HSG168: Fire Safety in Construction Work. While the latter tends to be focused on saving lives, the Joint Code of Practice primarily offers guidance in property protection. Its goal is to produce practical and cost-effective solutions to fire safety on sites employing established as well as modern methods of construction.
Though not mandatory, many insurers are asking for construction companies to adopt the code before they will insure them. So the first question that is always asked is, when does the code apply?
The answer is that it is applicable to all projects with an original contract value of £2.5m or above, and also applies to smaller value contracts where these are part of a large project. The code also applies to all parties involved in the project. The following is a summary of the new sections and additions in the 7th edition of the Joint Code of Practice.
Firefighters attend a blaze on a timber-framed building at a site in Tottenham, North London
Acetylene is a flammable gas that, at raised temperatures and pressures, or following impact to the cylinder, becomes unstable and liable to spontaneous decomposition. Acetylene in cylinders therefore constitutes a serious fire and explosion hazard.
The driver for this new section was the number of incidents where the fire and rescue services had to set up a hazard zone of up to 200m around the site of a fire involving an acetylene cylinder, a precaution that severely disrupted the smooth running of nearby businesses.
These incidents were a concern to fire brigades, because of the dangers to fire fighters exposed to such incidents, but also to insurers, because of the implications for business continuity of premises where it has been necessary to evacuate an area around an acetylene cylinder for a prolonged period. This has not only affected the construction site workers and employees at nearby businesses, but also the residents in the vicinity.
To avoid such incidents, the use of acetylene on construction sites should be eliminated wherever practicable, with alternative methods of cutting and welding being employed. Where the use of acetylene is unavoidable, the number of cylinders on site should be kept to an absolute minimum, the equipment maintained in good condition and cylinders adequately supported, for example by securing them on purpose-built trolleys using straps or chains.
High-rise construction sites
An increasing number of high-rise buildings are being constructed, especially in city centres. Working at levels which the fire and rescue services cannot reach in the event of an emergency clearly presents a significant threat to the lives of the building operatives. Even if there is adequate warning of fire, the time it takes to escape from upper levels to a place of safety away from the building may be considerable.
High-rise is defined in the code as a site beyond which the fire and rescue service cannot carry out a rescue by mechanical means, which is currently 30m from where a fire engine can be parked.
In a high-rise structure where the fire compartmentation is incomplete, fire spread may be much more rapid than anticipated. It is therefore necessary to undertake a fire risk assessment after consulting with the fire and rescue service to develop appropriate provisions before work starts at a height at which rescue by the fire service is not viable.
Where practical, the building should be fire compartmented horizontally at intervals of not more than 10 floors — apart from the stairways and shafts in which cranes are installed. This should be done at the earliest possible opportunity, using temporary fire prevention materials, until the permanent fire prevention arrangements can be put in place. Temporary fire stopping can be removed to allow construction operations in the area to be carried out but must be replaced whenever work stops.
The provision of adequate volumes and flows of water for fire fighting are required on all construction sites, but can create particular problems on high-rise sites. A reliable wet riser therefore should be provided and extended as work on the structure proceeds.
Modern methods of construction
The term “modern methods of construction” is used to encompasses many novel building methods, sometimes using new techniques or pre-formed materials.
The construction of hotels and similar buildings using factory-built pods has been standard for some years. While no new fire hazards are introduced in the process, there is a danger that even a minor fire damaging one pod at the centre of a large array could have implications for the programme of work on the site.
Timber frame buildings
Recently there has been several major fires on sites where large timber frame buildings — defined as being four storeys or more — are being constructed. These fires have developed and spread at an extraordinary rate. In one case, despite the fire brigade being called as soon as smoke was first seen, the building was at the point of collapse by the time fire fighters arrived. Not only is the threat to the structure itself extremely serious, but the intensity of the radiated heat from these fires has resulted in serious fire spread and even the complete destruction of neighbouring businesses and homes.
The structure is at its most vulnerable when the frame is in place with the insulation exposed and the building not yet weather-tight. At this time there is every opportunity, given the amount of ventilation in the open structure, for a small fire to spread rapidly.
Several of the major fires that have occurred on these sites are thought to have resulted from arson, and thus the security of the site and the structure itself must be a critical aspect of the fire risk assessment. Also, the proximity of the structure to the site boundary and surrounding buildings should be an important element in the risk assessment.
Every opportunity should be taken to mitigate fire damage and the spread of fire to adjacent structures by facing exposed timber construction and combustible insulation with non-combustible materials at the earliest opportunity. The use of such materials may be extended to protect windows and door openings not required as means of escape, an approach which also provides significant security benefits. In addition, the cladding to the building should be put in place as early as possible.
The high fire risk on sites with large timber-framed buildings required amendments in the code to the separation distance between these and temporary buildings such as site cabins. A fire break as wide as practically possible should be provided, subject to a fire risk assessment, with a suggested distance of at least 10m. On all other building sites, the fire break should be 6m where possible. If the distance is less than 6m the temporary buildings should be constructed from materials that cannot significantly contribute to the growth of a fire or the propagation of smoke or toxic fumes.
The products used in external walls and internal walls and ceilings should have a 30 minute fire rating and conform to BS-476-7, while the external roof surface should conform to Class AA in BS 476-3.
Experience, thankfully not involving injuries or loss of life, has suggested that there are shortfalls in the provision of audible fire alarms on some construction sites. The 7th edition of the Joint Code therefore makes additional requirements for the provision of manually operated fire alarms, hard wired call points and wi-fi linked fire alarm systems to ensure that the alarm is clearly audible over the whole of the site as work continues.
Similarly, there is also a call for adjustments to the distances for the storage of flammable liquids from high-risk buildings, with a minimum of 20m suggested.
Other amendments address the provision of designated smoking areas following the prohibition of smoking in the workplace and recognition that only in very exceptional cases should rubbish be burned on site — and even then it should be strictly controlled.
Despite the continuing problem of deliberate fires, over the past 18 years the number of major fires in the construction industry has decreased significantly. But changes to legislation, developments in the construction industry, the introduction of novel building materials and the constant need for vigilance against arson emphasise the importance of everyone involved in the construction industry working together. Steps must continue to be taken to minimise the likelihood of a fire occurring — and if one does, to reduce the cost to life and property and the disruption to people living and working in the area.
Wireless alarm put to the test
Kier Partnership Homes’ trials new approach at several of its construction sites
Kier Partnership Homes has trialled a new battery-powered wireless fire point system designed for the construction industry, which is quick to install and can be moved to a different locations as the build progresses.
The Wireless Emergency System from Ramtech wirelessly links multiple fire call points, so that the entire site can be alerted and evacuated as soon as a problem is encountered, and is activated and reset simply by lifting a protective screen and pushing a button.
This is Ramtech’s first venture into construction — its main market is providing alarm systems for caravan sites. Installation is simple and does not require an electrician or cabling. The system can also be tested without setting off the alarm, with an LED on each unit glowing if it has received the test signal.
New additions planned for 2011 include wireless smoke and heat detector units that can be connected to the alarm, and a more sophisticated base station that can send text messages to site managers — who may be temporarily offsite or at home outside site hours — to alert them to an incident.
Ben Buttarazzi, health and safety manager at Kier Partnership Homes, says the Wireless Emergency System has proved a useful addition to site safety measures.
“The device was tested in the most difficult of conditions on site interacting within masses of steelwork and concrete structures and performed above my expectations,” says Buttarazzi. “The quick installation and simple testing facility gives you peace of mind.”
Kier is also trialling the product at the £180m Featherstone Prison in Wolverhampton.
To avoid the possibility of two sites in the same vicinity using the same wireless frequency, each system is individually configured using a simple application on a laptop, with the data transferred to the units via a USB connector.
The system also means that the site can be split into separate zones. Each unit costs £260, although Ramtech also offers rental and service contract options.
Ramtech says the device is designed to be simple, cost-effective and robust. “The more complex the system, the more maintenance it needs,” says Andrew Bacon, research and development manager.
“Sales have increased every month since we launched the product in June.”
No cabling or electricians are needed to install Ramtech's wireless system
CPD test paper
Fire prevention on construction sites
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