Intumescent: Substances which swell as a result of heat exposure thus increasing in volume and decreasing in density. Intumescents are typically endothermic to varying degrees, as they can contain chemically bound water. Intumescents are used in firestopping, fireproofing and gasketing applications as well as closure components. Some intumescents are susceptible to environmental influences such as humidity, which can reduce or negate their ability to function. DIBt approvals quantify the ability of intumescents to stand the test of time against various environmental exposures. DIBt approved firestops and fireproofing materials are available in Canada and the US. 3M Canada is one such vendor.

Although somewhat contrary to the true definition, intumescents are categorised as passive fire protection measures. After all, there is motion, during the intumescing process and lots goes on chemically as well. Still, intumescents are used in compartmentalisation of fire, aimed at keeping fire in the fire compartment of origin. This is what qualifies them as passive fire protection measures.

A great deal of knowledge has been acquired on the topic of intumescents. There is also no shortage of manufacturers and distributors for intumescents, worldwide. The trouble is that many intumescent products don't work after they have been installed and exposed to common environmental conditions. An excellent source of information on the history and modelling efforts can be seen on the web under this URL: http://fire.nist.gov/bfrlpubs/fire97/art007.html, although it escapes me why anyone or who would want to model the effects of intumescents. Essentially, intumescents are used as listed system components in the field, regardless of the occupancy, whether this be in land-based construction, marine or offshore. One had better not rely on modelling for the performance of any system component in the field because they must be bounded, or in other words, installed in conformance with the maximum and minimum tolerances of a certification listing. Thus, one may run a model on any given scenario and reason that a 1/8" thickness is all that is required to obtain a certain rating, but this would be irrelevant information, since the installed configuration must be bounded by the certification listing. If the listing says 1/4", it is illegal to use any less. As far as interested parties for models then, that leaves the few of us, perhaps 30 to 50 people worldwide, who design test samples for the purpose of third party certification. For structural steel fireproofing, thickness calculations for spray applied fireproofing products are contained in the standards, such as ULC-S101 or ASTM E119. If one determines that a 1/8" thickness is required by calculation, to keep a beam below critical temperature (around 550°C, give or take, depending upon the country of certification) Beyond that, and for any other application, it comes down to a judgment call. Real testing routinely defeats models as well as engineering evaluations in fire protection. At best, results obtained through the use of a model can aid in making a judgment call prior to committing funds for a test. This would be a rare event indeed. I have yet to hear of one.

Also, if you enter the word intumescent into any search engine, you will come up with thousands of hits (as of 01/01, 2,830 pages on Altavista, 1,500 on Google, 4,084 on Lycos), primarily commercial advertisements for intumescent products. What is more difficult to find is what the problems are, the possible consequences, and how to avoid them. In the past, I have written an article on this topic for the Construction Specifier magazine, and had some emphatic responses for my raising of these issues, particularly from proprietors whose products did not possess the pedigree I suggested . And here is basically an update.

A closure is device or assembly for closing an opening through a fire separation, or exterior wall such as a door, shutter, glass block, and includes all components such as hardware, closing devices, frames and anchors. Closures may also be located inside of other closures, such as letter boxes within fire doors. Primarily in Europe, as well as countries which accept European imports, along with their certification, intumescents are being used either on their own or a primary components of other systems.

Some intumescents can be used only in very limited applications because their intumescing properties (and in some circumstances the applied intumescent in its entirety) can disappear within days of installation. The culprits here are the various environmental influences, such as humidity (even indoor, normal humidity!), UV, operational heat etc. Vulnerable intumescents, such as common sodium silicates (an exception to this being the expantrol sodium silicates manufactured by 3M) must be protected by epoxy or rubber coatings, to ensure operability. Responsible vendors of vulnerable intumescents clearly state that their products require protection and that if the protective layer is breached, one must immediately patch and make good. But not all manufacturers are that responsible and forthcoming. For instance, using commercially available sodium silicates (a chemical commodity widely available through chemical distribution houses), any moderately skilled entrepreneur could conceivably design a product, which will intumesce. But will it do so a week later, regardless of whether it be installed in a desert, a tropical jungle or the arctic? This is a significant factor, since some regions in Canada, for instance, can at times exhibit all of the aforementioned environmental conditions throughout one year. There have been a number of product recalls to date for faulty firestops - including in Canada and the US. Product recalls of passive fire protection components should give some pause to think. It's one thing when a car manufacturer recalls a type of car. You drive it to the dealer. The dealer fixes what is wrong, free of charge and you're on your way. But it's not quite that simple, when it comes to passive fire protection items, which are concealed behind the finishes of occupied buildings. Thus, we now know beyond the shadow of a doubt, that there are quite a few buildings out there, which have no fire separations, because you may rest assured, that not too many folks dug holes into their drywall and masonry and so forth to replace faulty firestops or to scrape deficient intumescent fireproofing off structural steel. Oftentimes, building owners are not well informed of the nature of such details, which have little to do with the overall purpose of the building. Thus, a great deal of caution must be exercised not only in the initial design of the formula, which should take into account the environmental exposures that the product may be expected to encounter, but also the standardised testing regime and quality control regime which should be enacted to provide peace of mind to the manufacturer, the end user, the design team and the contractors that the installed system will perform as intended in the event of a fire. Just because the product intumesces in the laboratory, does not mean, that it will actually be viable and can contribute to responsible fire protection practices. Since environmental exposure tests, which are the true test for intumescents, beyond the actual system fire test are mandatory in North America exclusively for steel columns tested to UL1709 the majority of products and systems utilising intumescents as prime constituents, are not required by law to be equipped with a pedigree that provides proof that they will work as soon as 1 week after installation. Product recalls are testimony to this trap, both in North America and in Europe. In one Canadian case, the manufacturer, an engineer by trade, who discovered an opportunity for his firestop "donut" product when he realise that plastic pipe penetrations were permissible in accordance with the National Building Code of Canada, went out of business around the time that a study into the longevity of his product was conducted by the University of Calgary, Chemical and Petroleum Engineering (11/92, Dr. E.L. Tollefson), which determined that the performance of his product was not predictable from one to the next, when subjected to assorted environmental exposures, after which the intumescence properties of the samples were quantified. In another court case in Vancouver, BC, an intumescent firestop sealant, used here in 2 hour fire-resistance rated floor slab through penetrations in a 20 storey high rise residential building, described in the literature as impervious to water as well as smoke migration, had been washed from penetration seals because rain had entered the construction site, after the product had supposedly cured. The distributor sued the contractor for lack of payment and was subsequently re-imbursed by the importer, on whose printed statements the installation was based. The product is still available in the marketplace today. Similar events have caused authorities (i.e. The German Institute for Building Technology - DIBt, Berlin, a federal government accreditation and approval body) in the Federal Republic of Germany to legally (and by definition) separate building products from listed or approved systems. Thus, if a system, utilising an intumescent component, is tested, after which the testing institute typically and automatically files for DIBt approval, will not be granted DIBt approval unless and until the intumescent product has received prior DIBt approval after successful completion of testing to the requirements of this document: "Zulassungsgrundsätze für dämmschichtbildende Baustoffe" ( in: DIBt Mitteilungen 1/ 1998) (meaning "Approval Guidelines for Intumescent Building Materials" from DIBt communications dated January 1998). And only in actual, real life ageing, DIBt based certification and UL1709 based certification, lies the solution to the problems associated with passive fire protection measures, which utilise intumescents as listed components. There are products, which offer a combination of such attributes (up to 2 out of 3) while many offer 0 out of three and still manage to meet the requirements of the building code because compliance with this certification regime is entirely optional in North America. Certainly none of this text is intended to imply that all or any North American made intumescents are generally inoperable. However, what will last where and for how long is something the prudent user as well as the developer of new products of this type must determine in order to avoid problems. Problems in fire protection can lead to catastrophic results.

In North America, the only standard, which adequately addresses serious environmental exposures and the longevity of intumescents is UL1709. Unfortunately, after the standard environmental testing abuse mandated by 1709, which also offers a variety of environmental exposure choices, UL1709 only covers fire testing of structural steel columns against the hydrocarbon time/temperature curve, which essentially restricts its use to fire protection measures intended for the protection of exterior steel structures in the oil and petrochemical market (a minority of applicable applications for intumescent products). In fact, testing against , UL1709 can frighten manufacturers of intumescents, and for good reasons, as you will see below. UL1709 contains one very tough set of tests, as it should, considering the harsh applications being qualified for (exterior hydrocarbon fire protection) and the enormous risk potential, such as fires in refineries and chemical plants. This test regime does nothing for interior products because no one has tested common interior passive fire protection products to UL1709. One of the reasons for this, in the case of intumescents, or even endothermic coatings, is that they generally contain a large concentration of epoxy, such that an unacceptably high amount of smoke is generated when the coating is first exposed to fire. Such a large fuel contribution violates building codes across North America. Thus, unless actual life data exists for the product one desires to use, for a sufficient length of time, in the application one desires to use it in, whether for interior or exterior applications, this leaves insistence upon products and systems, which possess DIBt building material approvals. There are other methods apart from that which is used by DIBt, but the best and most scientifically sound method for bench scale testing is the DIBt method. DIBt approved firestopping, fireproofing and gasketing products are available in North America and have been for some time. One such example is 3M, for its intumescent firestops. Another example is Nullifire, for its thin-film intumescent spray fireproofing product. UL and ULC committees are currently considering mandating the use of a watered down version of the DIBt method for benchscale testing of intumescent products used in firestopping applications. Neither the US nor the Canadian manufacturers (who make up the bulk of standard task group membership) are excessively enthusiastic about entering the environmental exposure criteria, which is actually the real issue at hand, when it comes to manufacturer due diligence as well as providing useful and reliable state of the art data to the end user. It is the costly environmental exposure testing as well as straight reality that causes some intumescents to fail.

First, UL1709 is intended to fire test structural steel columns, which have been protected with an exterior grade fireproofing material, for exterior use in the petrochemical field. Since the standard building elements time/temperature curve does not apply to exterior fires involving hydrocarbons, the so-called high-intensity or hydrocarbon fire curve is used. This means a much faster heatrise. Within the first 5 minutes of the test, 1,093°C or 2000°F must be reached. Then, this high temperature (1,093°C or 2000°F) is simply maintained for the desired fire-resistance duration, within a prescribed tolerance. The applied intumescent (or any other fire protective material intended to be classified for the same purpose) must keep the 2.4m (8') long steel column sample below 538°C or 1,000°F on average and none of the eight thermocouples must yield a temperature in excess of 649°C or 1,200°F.

Preceding the fire exposure test, is a whole battery of environmental exposures, some of which are mandatory. Once an exposure condition has been rendered, and the subject sample material is still intact, further testing can resume. The preamble to the "Simulated Environmental Exposures" indicates that simulated exposure conditions may include but are not limited to the following:

The sample is placed in a circulating air-oven at a temperature of 67.3°C to 72.7°C (153°F to 163°F) for a duration of 270 days or 9 months.

The sample is placed in an environment with the following conditions: 33.5°C to 36.5°C (92°F to 98°F) and 97 to 100% relative humidity for a duration of 180 days or 6 months.

The sample is placed in a chamber, where the 1% of the volume of said chamber must consist of SO2 (Sulfur Dioxide) and 1% of CO2 (Carbon Dioxide). Additionally, a small amount of water must be present at the bottom of the chamber, which must be maintained at  33.5°C to 36.5°C (92°F to 98°F). The exposure duration is 30 days, or 1 month.

The sample is exposed to salt spray (fog) testing in accordance with the methods described in ASTM B117-73(1979)

The sample is exposed to a simulated rainfall of 0.005mm/s (0.7"/h) for 72 hours (3 days), followed by a temperature of -37.3°C to 42.7°C (-35 to -45°F) for 24 hours, followed by a dry atmosphere or 57.3°C to 62.7°C (135°F to 145°F) for 72 hours (3 days). This cycle is repeated 12 times. One cycle takes 7 days, not accounting for breaks, times 12 times equals 84 days or 1.4 months.

The sample is exposed to a fog spray consisting of 2 % by volume of hydrochloric acid (HCl) in water. This fog spray must provide 1 to 2 mL of solution per hour for each 80 square centimetres of horizontal sample surface ares. The exposure duration for acid spray is 5 days.

Samples are sprayed with reagent grade solvents at 18.3°C to 23.7°C (65°F to 75°F). Typical solvents for this test are acetone and toluene. Utilising a standard spray gun, the solvent spray is applied until the entire surface area of the sample is completely covered with solvent and excess solvent is observed to run off the sample. ONE exposure cycle consists of the application of the solvent, followed by drying of the sample for 6 hours, followed by another solvent application, which is then followed by a drying period of 18 hours. This amounts to 1 day per cycle. The exposure cycle must be repeated 5 times, for a total test time of 5 days, not accounting for breaks.

In total, UL1709 testing, if one decided to run all of the environmental exposures, the testing would last 1 1/2 years, PLUS the ASTM salt fog spray. This duration, along with the costs are a large factor in the low number of vendors vying for this particular part of the market. Only one vendor has qualified his system to all environmental exposure criteria. This vendor markets an intumescent.

The main difference between the DIBt method and the UL1709 method is that DIBt applies generically to all intumescent materials, regardless of what passive fire protection systems or applications they may be used in (except that spray applied intumescent fireproofing has a unique set of tests), whereas UL1709 exposes the entire test sample to the aforementioned environmental exposures selected by the manufacturer or submittor. UL1709 is a system test, applicable to all products used to protect steel columns against the effects of exterior hydrocarbon fires, whereas DIBt's guideline is a bench-scale material test, suited exclusively to intumescents.

You can see a translated version of the DIBt standard at this URL:

http://www.geocities.com/ghering2000/dibt.html.

In short, DIBt's approach contains three sets of tests.

First of all, there are "basic tests". These establish sample sizes, sample construction, and densities. Once this is accomplished, the intumescence properties of the samples prior to any adverse exposures are quantified. An intumescent material, once exposed to heat, will exhibit three crucial characteristics in order to perform an adequate fire protection function. The importance of each characteristic varies with each product and application. First of all, the degree to which the intumescent is endothermic (how much water the formula chemically binds) is crucial for many fire protection applications. Once the water is gone, the unexposed side temperature will rise over 100°C, which is not far to typical failure mode, which hovers around 140°C for circuit integrity as well as fire-resistance. Secondly, the percentage of expansion makes a big difference. Particularly once all the water is gone in a fire test, one must then rely on the thermal properties of the char or foam created to keep the heat from becoming too high on the unexposed side. Additionally, maintaining a fully expanded char without any shrinkage or collapse is not for amateurs. Thirdly, the expansion pressure created by the intumescent is of significance particularly where the product plays a crucial role in closures such as plastic pipe firestops.

Each of the above mentioned three characteristics, are quantified in the DIBt method. Only products intended for use in pressure sensitive applications must undergo testing for expansion pressure.

The DIBt standard includes provisions for the use of two specific devices, which determine a product's foam height and expansion pressure. The drawings for these can be found at this website:

http://www.geocities.com/ghering2000/dibt.html

Apart from these most basic material characteristics, a combustibility classification is also made in accordance with DIN4102 Part 1. Further, products are evaluated as to whether or not they undergo a liquid phase early in the intumescence process. A judgment is also made on the efficacy of any outer protective coatings.

Secondly, samples can be exposed to a variety of adverse environmental influences. The idea is that products are tested only for those environments in which the manufacturer intends them to be marketed. The resulting DIBt approval (typically a precise, limited duration and multi-page document, which also indicates regular batch tests for certification purposes) will clearly spell out what can be used where) The environmental tests include the following:

-Short-term weather exposure

-Water condensate exposure

-Heat exposure

-Effect of coatings on the intumescent

(plastic dispersion, alkaline resins, polyurethane acrylics and epoxy resins)

-Effect of solvents and oil upon the intumescent

(butyl acetate, heating oil, butanol and test benzene)

Thirdly, the effect the intumescent has upon other building materials is tested. The materials listed for this test procedure are PVC and PE.

Once the samples have been exposed to these adverse environments, the basic characteristic tests are repeated upon the exposed samples. The difference in performance, both for foam height and expansion pressure between exposed samples and unexposed samples are recorded in terms of percentage. The idea behind the standard is that the testing be performed by governmental laboratories, which are DIBt accredited. Within the legal framework that this structure is based upon, test results are immediately communicated to DIBt, which forwards them to an expert committee (SVA) as a request for approval. Within the report, the laboratory must make a recommendation to the SVA on the eligibility of the product for DIBt approval. DIBt has indicated that the reason for this test and certification regime to be in place is that prior to this legislation, problems have occurred in Germany. Since the establishment of the legislation, there has been one update, but generally the system is proven to work. If there is a serious problem with an intumescent, this method is relied upon to find it. Additionally, the standard contains provisions to adaptation for unique products and unique applications. If the procedure has to be altered to more accurately determine its efficacy, changes can be made, but must be approved by the manufacturer, the DIBt accredited laboratory and ultimately the SVA expert committee. The same applies to the testing of environments, which are not adequately covered by the means established in the standard. For each change to the procedure, three parties have to agree. The DIBt method works.

Certainly all passive fire protection systems could benefit from this approach. Intumescents have been heavily penalised for some of their failures. But many good intumescent products are available now.

Intumescents are not unique in their susceptibility to environmental influences. It makes good common sense that when a product is exposed to a certain environment, one determine whether or not and how long for it can survive before its most crucial characteristics suffer. Both the UL method and the DIBt methods are excellent models for basic environmental testing of many products and many applications.

An emphatic NO is this author's response. The passive fire protection market is certainly not suffering from a lack of vendors for such products anywhere on this planet. If you are working for one, it is certainly wise to be up to date with the latest DIBt methodology. I recommend qualifying your products to this method and obtaining a DIBt approval regardless of where your product may be sold, even if it never reaches the German market, simply to prove due diligence as a manufacturer. If you may by purchasing intumescents for your facility or for re-sale or specifying them for use in someone else's facility, requesting a current DIBt approval (Baustoffzulassung) and/or a UL system qualified to UL1709 is prudent. Beware that for each standard, not each exposure is mandatory. Caveat Emptor!

Some folks will tell you that because their intumescents do what they do, it is not necessary to open up cable bundles and seal between cables. They would have you believe that the intumescent will swell in such a manner as to spread inside of cable bundles to make a smoketight seal. This is, of course, a physical impossibility. Cold smoke sealing (which saves lives and property, particularly electronic equipment) is based on firestop workmanship. Regardless of what the firestop is made of, it is imperative to seal inside the cable bundles. And with the whopping ten percent water that sodium silicate may contribute, the intumescent is not doing an excessive amount of cooling here either. The best cable penetration seal, apart from very small penetrations, is firestop mortar.

Easily the highest profile, biggest dollar market segment per job of all intumescents is the industrial exterior spray fireproofing market. All manner of passive fire protection products compete for this market, including intumescents, endothermic products, cementitious plasters, fibrous plasters, fibrous wraps, cast concrete, as well as active fire protection means, such as a sprinkler system providing coverage for an LPG (liquid petroleum gas) container.

Again, this puts us back in the oil patch and/or chemical plants, where we sport process pipe bridges (structural steel racks for the purpose of holding up process piping), vessel skirts (round steel sheet structures, which support a vessel above) and spherical or cylindrical LPG containers.

There is a definite demarcation line within such petrochemical facilities in terms of the importance (and thus willingness to part with funds in order to safeguard) given to pipe bridges and vessel skirts, versus the LPG containers. While, without vigilant enforcement measures, many LPG containers remain unprotected and still above ground (thus subject to fire exposure in case of a hydrocarbon spill, which may ignite), those facility owners who do in fact pay to fireproof their LPG vessels, are more likely, if aware of all technical, as well as cost aspects, to choose an intumescent or endothermic product, rather than a cementitious or fibrous plaster.  There are several reasons for this. One of them is longevity. Experience has shown that because of faulty dew point calculation and absence of compensatory measures (i.e. cost and interest reasons), fibrous plasters have become absolutely soaked with water, frozen, delaminated, etc. Next, cementitious plasters can for some products at times be proven by calculation to be able to absorb or move with the regular motion experienced by spherical LPG containers. This motion can be considerable, despite the sometimes up to 6" vessel wall thickness. As the sphere is emptied and filled, it definitely changes shape. The bigger the sphere, the greater that motion. Cementitious plasters used for spray fireproofing of spheres are typically re-enforced in the centre of the applied thickness, with a ferrous mesh, which is stud welded to the sphere, Allow for the re-enforcement factor, as well as the inherent flexibility of the plaster, which varies from one product to another, and it's nothing to write home about typically, and one may justify with a degree of margin, how one may safely fireproof an LPG sphere with a cementitious plaster. However, experience has shown that there have been failures, where the plaster has delaminated and the re-enforcement has corroded, to the point where the spray fireproofing has become dislodged and fallen off. Common factors known in inorganic chemistry, and particularly in the concrete industry, contribute to such events. If an exterior waterproofing membrane has been omitted, the thin, light weight and portland cement bound plaster will soon drop in pH value. This reduces the corrosion protection of the mesh, which starts to rust, expand and thus potentially damage the vulnerable plaster.  Also, installation errors are common, whereby basic cement chemistry is completely ignored. Such errors include excessive mixing of the plaster with water. For instance, it is not unheard of where workers have gone on lunch break, while 2 bags of plaster were still in the mixer. In order to save the material and still keep it workable, the mixer was kept running. By the time the material was finally applied, its principal binder was completely spent. Thus, spiderweb-like cracks soon appeared on the dry plaster surface. A toddler could soon remove it by simple touch. Often, insufficient attention is paid to the base epoxy coating (primer) of the metal. Before it became known how drastically and how soon the pH level of applied exterior spray fireproofing would drop, priming was at times omitted, in the belief that the pH level stated in the product data sheet of the cementitious plaster was sufficient to protect the substrate from corrosion. Such practices of course guarantee corrosion, which soon becomes evident by red leaks from the cracks of the remaining plaster. Add to this the corrosive effect of seashore installations, where more salt enters the plaster, and the life expectancy of such incorrectly installed systems is truly short. Thus, as an owner of a petrochemical facility, if you really really watch it, and not just go for the absolute lowest price, as is too often the case in all of passive fire protection, you may find successful cementitious plaster applications on spheres. But you would want to actually go and visit past installations, or speak to the person in charge of those facilities, particularly older ones, to be certain not only that the product is up to the task, and that the installer can point to past installations, which have been problem free, or where any problems were fixable and were indeed fixed without excessive effort. Intumescent and endothermic products for this application circumvent the problems associated with the aforementioned products, for the most part. There have been cases of misapplication, such as incorrect mixing proportions of ingredients, leading to the sliding off and then total replacement of the product - during the initial application. There have also been delaminations. However, these are much more of an exception and hence less of a factor albeit one should use caution to choose a financially stable contractor. Also, Intumescent and endothermic products are supplied in an epoxy paint base. Thus, they are inherently corrosion inhibiting. They are also much more likely to stretch and move with a sphere, as it is being emptied and filled and undergoing weather changes. There can be no water or chloride penetration and there is no cement stone to suffer from corrosive effects. There is a significant cost difference per square metre installed between fibrous and cementitious plasters, as well as  Intumescent and endothermic products. In light of the technical aspects,  Intumescent and endothermic products are worth the extra money, particularly when qualified to the environmental criteria of UL1709 or DIBt, which are appropriate to the application.