Passive fire protection systems are built into the load bearing structures to provide stability and into walls, shaft and floors to separate the building into areas of manageable risks, the so called “compartments”. Such protection is either provided by the materials from which the building is constructed or is added to the building to improve its fire resistance with protective materials (such as intumescent paints, sprays or boards).
It depends on whether there is a harmonized standard for specific use or not. For example, fire dampers have a harmonized standard, so CE marking is mandatory, while fire protective materials (such as spray, boards or intumescent paints) do not have it, so CE marking is not mandatory. Of course, the manufacturers may decide to CE mark their products on a voluntary basis, provided that there are specific guide-lines called EAD. The European Assessment Document (EAD) is the documentation of the methods and criteria accepted in EOTA as being applicable for the assessment of the performance of a construction product in relation to its essential characteristics. The EAD is developed in all cases where the assessment of a construction product is not or not fully covered by a harmonized technical specification.
The resulting CE marking is called ETA (European Technical Assessment: documented assessment of the performance of a construction product, in relation to its essential characteristics)
Fire is the ultimate in destructive forces and the sheer amount of damages and fear it can create is amaz-ing. The main consequences of fire are:
Death - this is a very real risk. Fire, and its consequences which are toxic gases and smoke, are extremely dangerous for human being. Every year more than 3.000 people are killed by fire in USA and about 4000* in Europe!
Injury - about 10% of all personal injuries reported each year are caused by fire. in Europe 190 people are hospitalized every day with serious fire injuries*.
Building damage - can be very significant, particularly if the building materials have poor fire resistance and there is little or no built-in fire protection. In Europe 126 billion €, or 1% of European GDP*, burned in fire costs yearly. In USA, the situation is even worse, resulting in damages and losses of $329 billion**, or 2.1 percent of the US gross domestic product!
Loss of business and jobs - it is estimated that about 40% of businesses do not start up again after a significant fire. Many small companies often cannot afford the time and expense of setting up again their activities.
Environmental damage - the fire and/or fighting the fire - fire-fighting water, the products of combustion can contaminate significant areas around the fire site.
*FSEU – year 2020 and NFPA year 2017
Manufacturer’s marketing information may not be sufficient to select the right material and, anyway, are not enough to comply with the fire preventing regulations. It’s necessary a valid fire report or assessment report, issued by accredited fire test laboratory against the local requirements. The most popular fire test and classification standards are: EN 13501-x in Europe, BS 476 or ASTM/UL in USA. In Europe, for products under a harmonized standard, so with CE marking for a specific intended use, it’s also necessary the Declaration of Performance (DoP).
In some country, specific third-party approvals are needed.
In Europe, and in several other countries around the world, the fire resistance is expressed though a classification according to specific criteria. Normally the fire resistance classification is followed by number which is the limit in minutes, such as 30, 60, 90 120 or 180, that shows the time the performance criteria is fulfilled during a standardized fire test. Most used classification are:
R –load bearing function Capacity of a structure to maintain its required mechanical resistance in case of fire.
E – Integrity Protection from fire and smoke but does not reduce the transfer of dangerous radiant heat in the event of a fire (integrity only performance)
I – Insulation The ability of a separating element of building construction when exposed to fire on one side, to restrict the temperature rise of the unexposed face to below specified levels
W – Radiation The ability of the element of construction to withstand fire exposure on one side only, so as to reduce the probability of the transmission of fire as a result of significant radiated heat either through the element or from its unexposed surface to adjacent materials
The criteria can be combined, for specific component or system:
EI Not – load bearing element that can offer protection from fire, hot gases and smoke and radiant heat for a defined period of time
REI Load bearing element that can offer mechanical resistance and protection from fire, hot gases and smoke and radiant heat for a defined period of time
EW Not – load bearing element that can offer offers an integrity performance (protection from fire and hot gases and smoke) whilst reducing transfer of dangerous radiant heat.
In other regions, the classification can be different, but the general concepts are the same or very similar for all the fire test standards and classifications.
CE marking is an administrative marking that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area (It is not a quality indicator or a certification mark).
In other words, the CE marking is the manufacturer's declaration that the product meets specific EU standards.
Flame retardants inhibit the spread of flames across a surface and/ or limit the contribution of a combustible material to a fire.
Fire retardant doesn’t have any direct influence on fire resistance, but only on fire reaction
Active fire protection is one of the fire protection’s strategy in which fires are detected, controlled or sup-pressed by means of motion or action. These measures attempt to eliminate fires and fire hazards as they occur rather than containing them as is the case through passive fire protection. Sprinkler systems or fire extinguishers are active methods of fire protection.
Durability: “the ability for long time performance” that in a technical language is defined as “the period during which a material, a product or a system maintain a given level of a performance, under specified conditions”
Durability means the capability of a building or of a product/system to perform its function over a speci-fied period of time, in specific conditions. All construction products have a limited durability
Implicit in the definition of durability is the assumption that regular maintenance will be carried out and that there will be no unusual events such as a large earthquake. Maintenance means the total set of activities performed during the design life to retain a building or its parts in a state in which it can fulfill its in-tended function. The durability of fire protective products can be assessed according to specific standard, for specific environmental conditions and for specific intended uses.
The fire resistance of a component or of a system, such as a steel column, a wall or a floor, is its ability to resist the effects of fire for a certain period of time. This time is usually measured by submitting the component or system to a standard fire test or is determined by calculation using specific codes, when permitted.
Passive fire protection is the most important defense in the preventing the spread of fire and it’s considered as a vital component of any fire strategy
Passive fire protection can, and does, save lives as well as property. Its aim is to contain the fire, hot gases and smoke within a compartment of the building, allowing the safe evacuation of the property and limit the financial impact of damage to buildings and their contents.
Many building materials, such as bricks, concrete or timber structures, have some natural resistance to fire and as such comprise built-in fire protection. This natural fire resistance may be improved by the use of protective materials (such as intumescent paints, spray, boards) or systems (fire rated walls and ceil-ings, shaft, etc.)
Generally the local Building Regulations, based on specific parameters that can be the fire load (the quantity of combustible materials), the dimensions of the building (mainly the high or the size of the compartments), the occupancies and/or the destination of the building (hospitals, schools, offices, etc.).
Compartment elements can be split in two main groups:
- Vertical partitions - Non-loadbearing partition walls are often brick or concrete walls or sandwich partitions and shafts. In some cases, the existing walls need to be upgraded to reach the fire resistance rating asked by the local regulation or by the specifier. Even loadbearing walls, such as concrete walls, could need upgrading to increase their fire resistance.
- Horizontal compartmentation - A natural horizontal compartmentation is the floor itself. If the floor on its own does not meet the fire resistance criteria, passive fire protection is then needed. The most common horizontal compartmentation systems are:
- Independent ceilings (ceiling membrane) – generally classified as “EI”
- Suspended ceilings, which give a contribution to the fire resistance of loadbearing elements (protective systems) – generally classified as R of the protected structure.
- Ceiling as component of a fire rated roof construction, with or without cavities – generally classified as REI (in this case the classification if for the whole system: slabs + ceiling and not for the ceiling alone).
- The designer does not fully understand the local regulations or the classification and/or test results of the solution.
- The designer misses to consider some weak points, like: penetrations, connections, electrical equipment inside the compartment element, dimensions larger than the maximum allowed for the specific compartment element, environmental conditions, etc.
- The designer is not aware or underestimates the limit of applicability or the field of application of the chosen solution.
- The designer does not have a holistic approach and misses to take into consideration the final environment: the conditions of use (for example children damaging walls in a school, or the necessity of frequent cleaning in an hospital, etc.), humidity, mechanical resistance, acoustic performance, etc.
- Missing to apply the procedures written in the classification /test reports or ignoring the instructions from the supplier.
- Missing to secure the weak points: cable penetrations, angles, doors, connections, inspection hatches, etc.
- Using the wrong materials and/or dimensions (“use the right boards or protective materials with the right accessories”)
Fire rated compartment elements shall fulfil one or more of the following criteria to prevent fire propagation:
- E: Integrity – ability to stop flames, hot gases and smoke from penetrating.
- I: Insulation – ability to restrict the temperature rise on the cold side. In most cases, the temperature at the cold surface may not increase more than 140°C on average, or 180°C, compared to the initial temperature.
- R: Loadbearing function – ability of a structure to carry loads or actions without collapsing. Only applicable if the fire compartmentation boundary has also loadbearing functions. In some particular cases, additional parameters can be required by local legislation, like W for radiation or M for mechanical action (resistance to an impact).
The fire resistance is always expressed in minutes, usually in classes that are multiples of 30 minutes. For example, a loadbearing compartment floor, that can withstand fire during at least 90 minutes will be classified “REI 90”, and a sandwich (non-loadbearing) partition wall that keeps the flames out and temperatures low during at least 60 minutes will be classified “EI 60”.
To keep a fire, hot smoke and gases where they are by creating boundaries to stop their propagation, leaving enough time for the occupants to escape safely. It is also meant to give time to the fire brigade to enter the building, check if all the occupants have actually left or help those who can't get out on their own, and then fight the fire itself before it spreads to other compartments.
Splitting a building into compartments also means that fire and smoke damage will be limited to the compartment involved in the initial fire, while the rest of the building, and the property it contains, will remain safe.
When local regulations require it, or beyond that, if you want to specifically preserve or protect certain areas of a building.
You can get the legal regulations for compartmentation from your local authorities or, in some countries, from the fire brigade. This is the best way to make sure you have the most up-to-date information.
Not only the product itself, but also all the related accessories (like studs that go with boards) are important. Promat offers a wide range of solutions for each and every application.
Usually, you can receive guidance from specialized study offices, fire experts and, in some countries, from the local fire brigade.
Your local Promat experts can also help you. Do not hesitate to ask your local technical sales team for advice.
Although the original objective is to avoid collapse or serious structural damage during an entire fire incident, national building codes define fire resistance of structures in time classes, e.g. 60, 90, 120, 180 or 240 minutes. In European standards, the fire resistance of a loadbearing structure is indicated with the letter R. For example, R120 means that a certain loadbearing element will not deform to the extent that it would jeopardise the stability of the structure during at least 120 minutes exposure to the standard fire curve.
Even if the probability that a fire would actually rage for (for example) 120 or even 240 minutes in the same location in a normal building is quite low, requiring such high fire resistance ratings effectively means that the probability of failure during fire is very low.
Although national building codes are different per country, they all require higher fire resistance classes for situations with higher risk, for example high rise buildings, hospitals, public buildings, etc. because more severe potential consequences (both in terms of safeguarding people’s lives and protection of the building and its contents) call for a lower probability of failure during fire, i.e. more fire protection.
The fire resistance of a structure is determined by calculation standards such as the Eurocodes EN 1992-1-2 (concrete), EN 1993-1-2 (steel), EN 1994-1-2 (composite) and EN 1995-1-2 (timber). Whenever an unprotected structure does not meet the required fire resistance rating, fire protection must be applied. The fire resistance of the fire protected structure is determined by test methods, such as the EN 13381 standard series, BS 476, ASTM E119, etc.
A correctly functioning fire protection system does not only depend on the availability of an independent test report or assessment, but also on the correct design where the fire protection system is used within the limits of that report.
The most common mistakes in the design are:
- Underestimating the actions on structures, including indirect actions, or overestimating the strength class of the steel, which leads to too high calculated critical steel temperatures.
- Not assessing the impact of localised fires, where temperatures can be very high, even if for a short time.
- Not considering the spalling effect for concrete structures.
- Using protective products outside their limits of applicability.
- Not properly evaluating test and classification tests of protective shields (suspended ceilings), whose functionality depends on many technical details.
- Not considering the robustness (or vulnerability) of the structures to be protected.
Apart from a correct design, the functioning of the fire protection system during fire depends equally on the correct installation.
Correct installation requires that the structure is accessible, that there is sufficient space to place and fix the fire protection system and that connections of different geometries don’t require very complex fire protection solutions.
The common mistakes are different for various types of systems. For example for board protection, the use of noggins of the wrong material such as wood, or inaccurate spacing or positioning of staples that connect the boards. For sprays and paints the application conditions are crucial: adequate cleaning of the surface, compatibility with primers, and application only when ambient temperature, relative humidity and substrate temperature and drying times between coats are within the ranges given in the application instructions.
When steel is exposed to fire, the thermal energy will cause the steel temperature to increase. The rate of temperature increase depends on the geometry of the steel:
- The greater the exposed external surface of the steel element, the faster the thermal energy will flow into the steel element
- The smaller the volume of the steel, the less thermal energy is needed to heat it up.
In European and British standards, both aspects are combined in the section factor, which is calculated by dividing the fire exposed external surface (in m2) by the internal steel volume (in m3). An alternative simple approach which gives the same outcome is to divide the exposed external perimeter (in m) by the cross-section area of the element (in m2). In ASTM standards, a similar approach is used where the calculation is based on the ratio between weight per linear foot (lb) and heated perimeter surface (inch).
Typically, section factors are in a range of 50m-1 to 300m-1. A low section factor means relatively slow heating, a high section factor means faster heating. Therefore, elements with a high section factor usually need thicker fire protection.
Even if a steel element is the same, the section factor can vary depending on some conditions:
Exposed surface: for beams under a concrete floor, only the sides and bottom of the beam are exposed to the fire. This is called “three sided exposure”. However a free standing column is exposed on four sides. Three or four sided exposure is reflected in the exposed surface which is used to calculate the section factor.
Box or contour protection: for sections with an H shape, the external exposed surface follows the contour of the H shape. However, if the fire protection consists of a rectangular box placed around the H shape, the external exposed surface is reduced to the size of the box. For intumescent paints and for sprays, the contour shape is relevant. For board protection, normally the box shape is used. For more information, please contact your local Promat office.
The notion of progressive collapse is important for loadbearing structures. It means that when one element collapses, it triggers the collapse of a next element, and so on to bring down larger parts of the building or even a complete building.
Progressive collapse can occur because if one element is weakened by the fire and fails, the loads (mainly the weight of the building and its contents) are redistributed to surrounding elements. It means that those surrounding elements undergo an increased load, which could in turn cause them to fail. Since the remaining elements decrease in number, the loads on those continue to increase. This process will often repeat itself, causing collapse potentially also beyond the part of the building affected by the fire.
As steel gradually loses its strength during heating up, at a certain temperature the remaining strength of a steel element will be insufficient to carry the mechanical loads, and the element will collapse. This depends on the utilisation degree: the ratio of mechanical loads under fire conditions that act on an element vs. its strength at room temperature. The higher the utilisation degree of an element, the lower the temperature at which it would fail.
In order to avoid failure of a steel element, the steel temperature must remain lower than the theoretical temperature at which failure would occur. The maximum allowable temperature that is low enough to avoid failure is called the critical steel temperature. The lower the critical steel temperature, the more fire protection is needed.
The critical steel temperature for each element can be calculated by a structural engineer, or safe values (typically 450-620°C) can be used based on local regulations. For more information, please contact your local Promat office.
The durability of a fire protection system, and therefore also the reliability over the life span of the building, depends on correct design and installation and on correct maintenance. When designing the building, it is crucial that the chosen fire protection system is resistant against weather conditions that it may be exposed to. Within the European Assessment Documents (EAD’s), the main weather resistance classes are Z2 (suitable for indoor dry conditions), Z1 (indoor humid conditions), Y (semi-exposed including freeze-thaw) and X (fully exposed), tested for a virtual service life of 10 or 25 years. Of course the real service life, even in the absence of ordinary maintenance, is much longer (generally multiplied by factor 2 or 3, according to European guidelines).
When installing the fire protection system, it is important that the installation instructions are carefully followed, and that for example water accumulation is avoided. Maintenance of a passive fire protection system is generally not required for indoor conditions. Whenever it is correctly designed and installed and not touched during the service life of the building, the fire performance remains the same. However if for example renovation works in the building lead to damage of the fire protection system, it needs to be correctly repaired.
For more information, please contact your local Promat office.
Making sure that the building structure, or parts of it, do not collapse or suffer serious structural damage during fire. Only under these conditions, the compartmentation can contain the fire, people can escape, the fire brigade can search the building for survivors and possibly fight the fire, and destruction of valuable assets is limited. Therefore, fire resistance of the loadbearing structure is the basic condition for fire safety of any building.
Although concrete heats up relatively slowly during fire, there are still ways that a concrete element can fail. The most common failure mechanism is when the concrete cover on the steel reinforcement is not thick enough to keep the reinforcement temperature down. This is often the case for old buildings and for buildings with very high fire resistance requirements. Fire protection can compensate for the lack of concrete cover thickness.
However, in cases where concrete is exposed to humid environments and/or potentially more severe fire temperatures, spalling of concrete poses an additional risk. Spalling of concrete causes quick and explosive detachment of layers of the concrete structure, usually occurring in the first 5 to 30 minutes of the fire, even if the temperature is still quite low, and exposing the steel reinforcement directly to the flames. In such cases it is necessary to apply fire protection to make sure that the concrete temperatures remain low and spalling does not occur.
When steel is heated to temperatures of 400°C to 800°C, its strength gradually decreases. The stiffness of steel decreases already starting at 100°C. The reduction in strength and stiffness will cause large deformations and eventually collapse of building elements. As steel structures are generally slender and steel has a high thermal conductivity, they tend to heat up fast when exposed to fire.
By applying a protective shell around the steel element or a fire shield such as a fire-rated suspended ceiling, the heating up of the steel is delayed and collapse can be postponed or avoided.
When a timber element is exposed to fire, the material starts to burn at the surface. Gradually a layer of char (burnt wood) is built up. Over time, the layer of char becomes thicker and the remaining cross section of timber decreases. The speed of this process depends mainly on the type of timber and the humidity (moisture content).
The remaining cross section must be able to carry the mechanical loads on the structure. Moreover, a small zone of this unburnt cross section just below the char is so hot that it doesn’t have strength left.
Slowing down the heating and charring of the timber is key to extending its fire resistance. A fire protection material acts in two ways:
- Instead of starting immediately, the formation of a char layer is postponed.
- Once the char starts to form, this process is slowed down.
With these two beneficial effects, the fire resistance of the timber element can be extended to meet the required fire resistance time.
Even if firestop systems are tested at very high temperature (usually more than 1.000°C.), these tests are under fire conditions (so with a growing fire curve up to 2 or even 4 hours maximum) and not day to day constant exposure to high temperatures. Most firestop systems start to react, changing chemically or physically at relatively low temperatures (100 to 200°C), such as the intumescent materials and the endothermic coatings. Therefore, these products cannot be used as “high temperature sealant”.
Basically the coated batt systems are tested with all edges covered and all joints filled with coating. The edge cover is important to ensure good stickability to the substrate and close any open spots to prevent from passage of fire and smoke. Only annular gap seals are closed with acrylic.
Where can I find installation instructions? Visit www.promat.com and download from documents the relevant guideline or video.
Compartmentation is designed to prevent the spread of fire and hot smoke to the next compartment and to allow safe evacuation in the rest of the building. Evidently this cannot work if there are holes and gaps in fire-rated compartment elements, because even the smallest hole can allow smoke or flames into the adjacent compartment. Firestop systems could either be:
- Intumescent systems: generally used to compensate the melting or reduction of volume of services (services containing plastic) that pass through compartmentation elements or for joint protection.
- Passive systems: generally used to isolate elements that, potentially, can conduct thermal energy trough a compartment elements by conduction (services containing metal) or to close large holes.
- Mix systems: combinations of different systems such as intumescent, insulating, ablative or other for special applications
Sprinkler systems are important component of active fire protection, but they are designed to control the fire and in some specific case to suppress the fire, but not to contain it within the compartment. Sprinklers cannot stop smoke or toxic gas from spreading during a fire. The scope of firestopping, instead, is contain the fire within the compartment, while also preventing smoke from travelling through the compartment elements.
Plastic pipe is a very general term. It is important to know the type of plastic pipe and its diameter and pipe wall thickness. The firestopping systems are tested for different types of materials (i.e.: PVC, PE, PP, multilayer pipes) with different diameters and pipe wall thicknesses and each variation must be properly tested and classified.
The following factors should be considered:
- Type of compartment element (concrete, drywall, masonry, …?)
- Is it a wall or floor? Any other construction element?
- Which fire rating is required? Integrity and insulation?
- Dimension of the openings? How many? How big is the annular gap?
- Which services are passing through the penetration? Single cables, cable bundles, cable trays, cable conduits, cables in plastic/metal tubes, combustible pipes, with or without sound decoupling, with or without insulation, with coupling, angled pipes (degree?), non-combustible pipes, with or without insulation, ventilation ducts, with or without fire damper, combination of above services;
In general, each individual system requires a specific product. More specifically, these are the main questions to be answered before choosing the most efficient system.
The definition “intumescent” indicates that the material has an expanding capability when exposed to fire or heat. Intumescent materials are used on penetrating materials that would burn or melt away during a fire such as plastic pipes, low melting materials (eg combustible insulation) or cables. Even in cases where the penetrants do not burn or melt, intumescent materials offer the advantage of being able to expand and seal many cracks or gaps that may have developed or be the result of improper installation. Do not be confused with "endothermic", which are products that block heat by chemical absorption and moisture release.
This is an aperture in the separating element which is sealed or closed by the specified seal without incorporation of penetrating services.
This is a horizontal or vertical supporting construction consisting of studs or joists, including linings and optional insulation.
This is a system used to maintain the fire resistance of a separating element at the position where services pass through or where there is provision for services to pass through a separating element.
A penetration is an aperture in a separating element for the passage of one or more services.
This is a mechanical support provided in the form of clips, ties, hangers, ladder racks or trays, or any device designed to carry the load of the penetrating services.
These are systems such as a cable, conduit, pipe (with or without insulation) or trunking.
A firestop system is a combination of products, which are used to seal openings around services and joints in a fire rated compartment, which could be walls, floors, shafts, etc. to prevent the spread of fire and smoke.
Firestop systems are installed in all openings, gaps or joints in a compartment and must have the same fire resistance (or higher) than the compartment.
The importance of penetration seals cannot be overstated. Experience shows that penetrations tend to be the weakest link in the chain of compartmentation within buildings. We should all be aware that in such building compartments the most likely threat from the spread of fire will occur where services penetrate walls or floors, or where concealed cavities between separating elements interlink. Unfortunately, the lack of seals, incorrect specification and incorrect installation has contributed to many large fires in all buildings, both new and old, which would not have been so destructive if the penetrations through compartment walls and floors had been adequately sealed against the passage of fire and smoke, or that seals had been properly specified.
In Europe, smoke control ductwork can be:
- Horizontal single compartment ducts, which can be used in one fire compartment only and are tested according to EN 1366-9, under a specific 600°C time/temperature curve and classified according to EN 13501-4
- Horizontal or vertical multi compartment fire resistant smoke control ducts, which can be used in any number of fire compartments and are tested according to EN 1366-8, under ISO 834 curve and classified according to EN 13501-4 (as “duct C”)
The test method for multi compartment fire resistant smoke control ducts (EN 1366-8) is applicable to fire resisting ducts that have already passed the appropriate period to EN 1366-1 (Ducts A/500 Pa and B). For mono compartment ducts, only test according to EN 1366-9 is required.
These test methods are suitable only for ducts constructed from materials class A1 and A2-s1, d0, according European fire reaction classification.
In Europe, ventilation ducts are tested according to EN 1366-1 and classified according to EN 13501-3. The standard heating curve is described in EN 1363-1 (ISO 834). The classification contain indication about Integrity and Insulation (EI) and is completed by “i → o” (so called duct A), “o → I” (so called duct B)’, or “i ↔ o” (duct A/B), to indicate whether the duct has been tested and fulfils the requirements with fire from the inside or outside only or both. Moreover, the leakage is monitored.
The type of smoke ventilation systems are:
Natural smoke ventilation systems
They use the inherent buoyancy of hot smoke and the airflow dynamics of smoke and air to remove smoke. The so-called Automatic Opening Vents allows smoke to escape from the building when a fire is detected, as they are automatically opened.
Mechanical smoke ventilation systems
They use powered fans elements to force the movement of smoke and to allow it to be removed from the building, generally through smoke extraction ducts. They provide an alternative to natural smoke ventilation systems to create smoke free escape routes for occupants and access for fire-fighting services. When smoke it detected, only the damper of the ductwork on the fire floor will open (all others remain locked shut). The fan at the top of the ventilation system extracts the smoke and prevents migration of smoke into the adjacent compartments.
Smoke and Heat Exhaust Ventilation Systems (SHEVS)
whether these are powered or natural, these full systems remove smoke from the building. They are mainly composed by inlet ventilators, dampers, ductwork and fans or automatic opening vents.
Ventilation system with jet fans
Jet fans can clear from smoke large compartment or, as in most of the cases, just move it in a specific part of the compartment for a certain time, allow people escape.
Smoke Containment Systems.
These systems, often curtain or physical barriers, prevent the movement of smoke and heat from one area of compartment to another.
ISO has defined fire effluent as the “totality of gases and aerosols, including suspended particles, created by combustion or pyrolysis in a fire”. Fire effluents can be classified into four main categories: asphyxiant (narcotic) gases, irritant gases, sub-acute toxicants and sub-lethal toxicants.
A wide range of common materials used in modern buildings produce a mix of combustion products, which can have an adverse effect on human health and the environment. Exposure to some compounds may show both acute on sub-lethal or sub-acute effects.
Ventilation and smoke extraction ducts can be tested according to different standards. The most common are European Standard (EN 1366-x), British Standard (BS 476) and American Standard (UL /ASTM).
The performance criteria according to European Standard are the followings (similar criteria are considered in the other test and classification standards):
Leakage
The duct shall not have a leakage exceeding 10 m³/h per 1 m² of internal surface area. This shall be related to the surface area of the duct from the perforated plate to the end of the duct by the inlet nozzles.
Integrity
The integrity at the seal/penetration between the duct and the supporting construction shall be judged in accordance with EN 1363-1 (cotton pad test and gap gauge).
Insulation
Test results shall demonstrate the insulation performance of the duct (typically 140°C average and 180°C maximum above room temperature on the external duct surface in the compart adjacent to fire
Reduction in cross-section
The internal dimensions (width and height for rectangular ducts, diameter for circular duct) of the smoke extracting ductwork shall not decrease by more than 10 % during the test.
Mechanical stability (only for smoke extractors)
If the duct inside the furnace collapses, so that it can be judged as not being able to maintain its smoke extraction or fire resistance function, this shall be regarded as failure under the mechanical criterion.
A well designed smoke control system can save lives and help protect property. More specifically, it will:
- Delay or prevent flashover, reducing the risk of the fire developing further.
- Keep escape and access routes free from smoke.
- Facilitate fire-fighting operations.
- Reduce the risk of damage to the building.
- Protect the contents of the building.
Fire fatalities are often smoke fatalities. In fact, the most frequent cause of death or injury in a fire is smoke inhalation. According the U.S. Fire Administration (USFA), smoke is the killer in 60% to 80% of all fire deaths. Irritating, toxic and asphyxiant gases can lead to unconsciousness in few minutes and eventually to death.
There’s no fire in buildings without smoke: a rooms can quickly fill with smoke and gases in the event of a fire. Only 300 gr of paper (the weight of a single book!) can produce more than 300 m³ of smoke and gases when burned (the volume of a 10x10x3 meters office). Even a burning wastepaper basket can quickly fill a room with smoke.
The development of smoke and gases in a room or even in a large space is dramatic: the first effect is reducing visibility, normally in two, three minutes. The consequence is that people cannot find the escape route and panic often start. The second effect is related to toxicity of specific component, such as carbon monoxide (CO). Inhaling carbon monoxide leads to nausea or vomiting, confusion, loss of consciousness and ultimately death. Depending on the materials present in a building, some other dangerous gases can be released such as hydrogen cyanide, hydrochloric acid, ammonia, etc.
Smoke is also the biggest enemy of fire brigade.
Ventilation ducts provide possible routes for smoke spread between adjacent rooms or compartment in case of a fire. Fire spread from one fire compartment to another (e.g. between floors) must be avoided to keep the building safe and to give tenants the necessary time to escape and to the fire brigade the time to control the fire. Specifically in ventilation systems, the smoke and fire spread can be prevented installing dampers or smoke/fire barriers and shut down the ventilation system in the event of fire. This is not always the best cost-effective solution. Moreover, it must be considered that typical steel sheet ducts can be deformed rapidly from the effects of fire, creating potential collapse of the vertical compartment element, especially if are light partition, and/or leaving a space around the penetration onto the walls and ceilings where fire and smoke can easily pass.