Fire! Remove the smoke, improve your chances of survival
The lethal effects of smoke inhalation have been known as far back as the first century AD when Pliny reported that the Romans executed prisoners by placing them in cages over the smoke of greenwood fires.
Fast forward to the 21st Century and the UK Government’s Department of Communities and Local Government statistics states, ‘The most common cause of death from a fire incident is being overcome by gas, smoke or toxic fumes.’
The thick black smoke inhibits visibility and can introduce panic and disorientate anyone trapped in the building. They are quickly rendered unconscious when inhaling this smoke and therefore are unable to escape. For survivors, the burns from a fire are obvious injuries; however the toxic combination of carbon monoxide, hydrogen cyanide and other combustion products cause injuries to the lungs and airways that are not so apparent and may not present until 24-36 hours after exposure. Recently, two factors have contributed to an increased threat to life from the perils of smoke;
As society has become more affluent there has been a corresponding increase in the amount of furniture, electronic gadgets and possessions in general within buildings. Over time these have transitioned from being comprised mainly of natural materials to being dominated by synthetic materials.
This is equally relevant in commercial premises as it is in domestic dwellings. As pressure is placed on the availability of land for new construction, existing workstations get smaller and more people are squeezed into office space or manufacturing workplaces. At home, imaginative ways are constantly sought for building more residential units on a given plot of land.
Regulations imposed on the furniture and furnishings industries to apply fire retardants to their products’ coverings mean that these now smoulder instead of igniting instantly. The smouldering produces smoke and, when the furnishings do eventually catch fire they burn differently, releasing many different chemicals and different toxic gases. This is commonly known as a chemical fire.
Modern methods of construction
The construction industry is continually introducing new engineered products that provide better structural stability, allow for faster construction time and that are more cost effective. The continuing trend towards green or environmentally sustainable building materials has grown enormously in recent years and the UK Government is committed to all new build homes being ‘Carbon Neutral’ by 2016.
These factors all seem to rank higher than life and fire safety because they create changes in the fire environment, and how these changes impact on fire behaviour is something that we know little about currently. Whilst these buildings are compliant with Building Regulations at the time of completion, once occupied, fire safety can be compromised, so built-in robust smoke management systems are vital. Experiments carried out in the United States compared this impact of changing fuel loads in residential houses. These experiments showed that living room fires have flashover times of less than 5 minutes when they used to be in the order of 30 minutes. The response times for the emergency services have never been so critical.
Globally, firefighting technics have evolved to make the removal of the smoke a high priority. Positive pressure ventilation is designed to drive the smoke from a building fire and therefore remove the threat of backdrafts and flashovers.
Most larger buildings, such as a shopping mall, Hypermarket or underground car park, contain enough air flow to sustain and develop a fire and so it is incumbent upon the building owners to ensure that, should a fire break out, the occupants are able to evacuate speedily and efficiently. A smoke control system has the following basic objectives;
- To keep means of escape free from smoke
- To delay the build-up of pressure that may lead to a flashover
- To assist the emergency services when they arrive on scene
- To reduce smoke and heat damage to the building structure and contents
For these large buildings, with large open areas, specialist Smoke Ventilation Consultants will design a ‘Fire Engineered Solution’. This will use a combination of mechanical smoke extraction vents, smoke barriers and air inlet vents to ensure that, in the case of a fire incident, the smoke is vented allowing the occupants to locate the exit routes and leaving a layer of clean air below which people are able to pass and exit the building safely.
For smaller buildings there haven’t been so many options for pro-actively venting the smoke. Automatic Opening Vents have been around for some time but they tend to require manual activation. However the innovative Naturvent System from Ash Fire Management has been specifically designed as a pro-active smoke ventilation system for residential and smaller commercial buildings.
The Naturvent system utilises state of the art smoke and carbon monoxide detectors to sense the early stage outbreak of a fire. It simultaneously raises the alarm, notifies the Emergency Services and others as well as releasing the hatches in the roof that extract the smoke from the building.
As featured in January’s Means of Escape newsletter, the Naturvent System was showcased earlier this year in a series of demonstrations at the North Weald Airfield, Essex. Senior executives from a broad range of businesses and organisations within the Fire Sector witnessed how this innovative system extracts the smoke and thereby maintains visibility within the means of escape during a simulated house fire.
Identical fire loads of synthetic and natural materials were ignited inside a rubbish bin placed centrally within the downstairs room. For the first fire, without the Naturvent system activating, the visitors saw how quickly the house filled with the thick, black smoke. Then, after a short break to ventilate the house, the second fire was ignited but with the Naturvent system switched on. The fire detection system soon raised the alarm and the system activated to enable the smoke to disperse from the building and leaving the staircase, the means of escape from the upstairs rooms, clear. A video of the event can be viewed here.
These demonstrations involved ‘controlled burns’; however the Naturvent system has been thoroughly tested at the Building Research Establishment with a fire ignited in a downstairs room containing furniture typical of a small residential house. The test data from these results show that the Naturvent system maintained tenable conditions for 18 minutes longer than when an identical fire was ignited but without the Naturvent system installed. With the alarm raised this is sufficient time for an able-bodied person to escape from the building or for someone to be rescued from the building.
An additional benefit of the Naturvent system is that it will provide a safer operational environment for the fire and rescue service when they arrive on scene. With improved visibility and a removed threat of a flashover or backdraft, they can locate the seat of the fire quicker, rescue any trapped persons and extinguish the fire. Improving the chances of survival and also reducing damage to the property.
Although the Naturvent system was designed with life safety as its uppermost priority, it is not just the residential sector that is benefitting from the Naturvent system. Schools, waste transfer stations, care homes, nightclubs and public houses are examples of organisations and businesses that see Naturvent as a valuable tool for protecting occupants and property from the threat of smoke and fire damage, should the unthinkable happen.
Smoke has been, and continues to be, the greatest threat to human beings in a fire scenario. Whatever the circumstances, the threat of the deadly consequences of smoke inhalation must be removed from a building, and the Naturvent system has been tested and proven to be a vital asset in its removal.
For more information on the Naturvent System, or Smoke Management Systems generally, call Paul Evans on 07792 628510 or email [email protected]
View the vide here
Published October 2015
The lethal effects of smoke inhalation have been known as far back as the first century AD when ...