Animal studies provide most of what we know about the dangerous effects of toxic substances. VOCs and Other Toxic Chemicals in Mattresses: What to Know As polyurethane foams have very low thermal inertia, application of heat or a small flame can be enough to ignite them. Taking this into consideration, the reported yields of isocyanates, aminoisocyanates and amines are still relevant, as the results of Blomqvist et al. (1969) reported the decomposition of rigid polyurethane foams in both nitrogen and air to assess the production of CO, HCN and NH3. Similarly, well-ventilated fires are generally small, and of low toxicity. Additionally, the authors reported a yield of 1315mgg1 of CO, 1.41.5mgg1 of HCN, and 1012mgg1 of NO. \( \phi =\frac{actual\; fuel\;to\; air\; ratio}{stoichiometric\; fuel\;to\; air\; ratio} \). However, spray foam insulation is a highly energy-efficient product and quickly offsets its manufacturing footprint. (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. Substituted ureas decompose between 235 and 250C and carbodiimides decompose between 250 and 280C. J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. Allergy 63:p583591, Pitts WM (1995) The global equivalence ratio concept and the formation mechanisms of carbon monoxide in enclosure fires. It can continue to irritate people sensitive to chemicals or odors . Polymer Degradation and Stability 93:p20582065, Tewarson A (2002) SFPE Handbook of Fire Protection Engineering, 3rd ed. NBSIR 822532. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. Spray Foam Insulation: Helping Achieve Sustainability. Damage was most severe to the exterior. Off-gassing & Outgassing: What's the Difference? Where is it From As with all foams, memory foam compresses under pressure. Is Polyurethane Foam Toxic, And Should You Avoid it? - The Safe Parent A more recent assessment by Marsh and Gann (2013) tested a flexible polyurethane foam with a cotton polyester cover in a range of test methods including the radiant heat apparatus (NFPA 269 2012), the ISO 56592 (2012) smoke density chamber, a controlled atmosphere cone calorimeter (ASTM E 1354) and the steady state tube furnace (ISO/TS 19700 2013). Fire Res 1:p1121. The cone calorimeter (ISO 56601 2002) is probably the most widely used apparatus for measurement of flammability properties such as ignitability and heat release rate (Schartel & Hull 2007). Unfortunately, your body heat appears . Thermal Decomposition of Polyether-based, Water-blown Commerical type of Flexible Polyurethane Foam. (1972) suggested that the decomposition was initiated by the release of a nitrogen-rich material at 200300C which in turn decomposes into low molecular weight nitrogenous fragments above 500C. Generalised decomposition mechanism for polyurethane foams both in nitrogen and in air. Ask Pablo: How Bad Is Memory Foam? Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. The production of HCN and other low molecular weight nitrogenous compounds from the high temperature decomposition of polyurethanes has been reported in the literature in recent years. In the case of flaming combustion, one of the most important factors relating to the toxic product yield is the fuel/air ratio which, as defined earlier, can be expressed as an equivalence ratio (). However, once one of the groups forms a urethane or urea, the activating effect on the other isocyanate is reduced, as ureas and urethanes are weaker activating groups than isocyanates. Investigations by Hertzberg et al. This is due to the concentration of oxygen directly under a flame being close or equal to 0% (Schartel & Hull 2007). False True. The results showed a HCN yield of 15.8mgg1 at 600C. Woolley et al. Toxicology 115:7, Henneken H, Vogel M, Karst U (2007) Determination of airborne isocyanates. The polyurethanes used were elastomers based on TDI, which could potentially have differing decomposition mechanisms to their foam counterparts. 2012). However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. 2005; Blomqvist & Lonnermark 2001). The interior of large flames are always under-ventilated, because oxygen cannot penetrate the flame. In order to relate the fire effluent toxicity to a "maximum permissible loading", the FED can be related to the mass of material in a unit volume which would cause 50% lethality for a given fire condition. Download resource By using infrared analysis, the authors were able to detect a range of compounds at each step, as summarised in Fig. HCN yields reported in under-ventilated conditions vary depending on the composition of the material; with flexible foams producing less than rigid foams and polyisocyanurates producing the most overall. Work published as early as 1959 supported this mechanism of decomposition at higher temperatures and noted that up to 70% of the nitrogen in the foam could be converted to HCN at 1000C (Saunders 1959). The main toxic combustion products can be divided into two classes: asphyxiant gases, which prevent oxygen uptake by cells, with loss of consciousness and ultimately death; and irritant gases which cause immediate incapacitation, mainly by effects on the eyes and upper respiratory tract, and longer term damage deeper in the lung. This steric hindrance can be offset by increasing the temperature of the reaction or by performing the reaction in the presence of a catalyst (Vilar 2002). NBSIR 832719. While well-ventilated fire scenarios are routinely used for assessment of flammability, because the object is to stop the fire growing to the out of control stage, where fire toxicity is concerned, the important fire stages are under-ventilated. Fire Safety Journal 43:243251, Piiril PL, Meuronen A, Majuri ML, Luukkonen R, Mntyl T, Wolff HJ (2008) Inflammation and functional outcome in diisocyanate-induced asthma after cessation of exposure. The full-scale test showed good accordance with the SSTF data considering the inherent unreliability of large-scale testing. Around 1015% of the nitrogen in the polymer can be converted into HCN with some being released in isocyanates, aminoisocyanates and amines in the fire effluent. The results of these experiments and the mechanism of decomposition derived correlated well with work by Rein et al. Both types of foam yielded very similar products at temperatures above 600C. HCN analysis was performed using infrared (IR) spectroscopy using a short path-length gas cell, which is a questionable method for the quantification of HCN due to its poor IR absorption, high potential for interferences and a poor limit of detection. 1982) to that of a large scale test room. FED model from ISO 13571, Equation 1 The results from the SSTF and FPA show the best agreement with those from the full and 1/3 scale ISO room for both materials under a range of fire conditions. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme 5). Anal Bioanal Chem 387:p219236, Herrington R, Hock K (1998) Flexible Polyurethane Foams, 2nd edn. This slight decrease is probably within the limits of experimental error, as it does not follow the general trend shown by most materials. This resulted in the reported HCN yields for the under-ventilated conditions being lower than expected in all of the tests. Do memory foam mattresses give off toxic fumes? 8). National Fire Protection Association, 82, p 161, Vilar WD (2002) Chemistry and Technology of Polyurethanes - Chapter 1. 2008), where inhaled isocyanates rapidly form conjugates with epithelial lung cell proteins (Wisnewski et al. (2013) further supported the presence of two separate decomposition mechanisms for flexible foams. 1). The authors intended to compare the HCN yields for the non-flaming and flaming combustion of the foam in a smoke chamber apparatus (as described in Levin et al. The findings from these studies demonstrated that yields of different toxic products are highly dependent on equivalence ratio (either positively or negatively correlated), and elemental and molecular composition of the material. This is unusual as this test method is usually well-ventilated and the results are not similar to reports of other authors (such as Levin et al. Most fire deaths and injuries actually occur in residential fires, although assessment of fire toxicity is currently focused on areas where escape is restricted, such as aeroplanes, railway carriages, and passenger ships, which include requirements to quantify the fire toxicity of internal components. 1982), a developmental method (SwRI/NIST method) which used a radiant heater on the sample which lead into a 200 L exposure chamber, a cone calorimeter (ISO 5660 2002), a furniture calorimeter (as described in Babrauskas et al. This suggests that any amines formed would have reacted with isocyanates in the vapour phase to form ureas, some of which would have condensed to produce the observed waxy white substance. Respiratory Issues First, polyurethane is a petrochemical resin that contains known . DiNenno) Fourth Edition. However, a non-standard modification of the apparatus has been described, enclosing the fire model in a controlled ventilation chamber, in an attempt to replicate oxygen-depleted conditions. Journal of Fire Sciences 8:p6379, BS 6853 (1999) Code of practise for fire precautions in the design and construction of passenger carrying trains. The reaction of an isocyanate functional group with water (Scheme2) results in the formation of an unstable carbamic acid group, which in turn decomposes to release an amine and carbon dioxide. Smouldering was forced by an electrically heated resistance wire embedded in the sample and a load cell measured the mass of the sample throughout the experiment. 9). Cookies policy. Combustion Science and Technology 183(7):p627644, Saunders JH (1959) the Reactions of Isocyanates and Isocyanate Derivatives at Elevated Temperatures. At >800C these compounds further fragment into simple molecules (such as HCN, CO, CH4 and CH2O) and PAHs. In addition totheir flammability, polyurethanes form carbon monoxide, hydrogen cyanide and other toxic products on decomposition and combustion. Furniture, upholstery and curtains ISO 19706 (2011) Guidelines for assessing the fire threat to people. However, there is verylittle literature available regarding the yields of isocyanates produced by the combustion of polyurethane foams. The three-compartment test consisted of a 2.43.72.4m burn room, a 2.44.62.4m corridor and a 2.43.72.4m target room where samples would be taken. International Maritime Organisation, London, Garrido MA, Font R (2015) Pyrolysis and combustion study of flexible polyurethane foam. New memory foam smell? The heating of polyurethanes in an inert-atmosphere results in the progressive rupturing of bonds as a function of temperature. The flexible foam produced ~175mgg1 of CO and 5mgg1 of HCN. Reliable rate of heat release, fire effluent toxicity and smoke generation data are all essential components of such an assessment. As the toxic product yields of polyurethane foams are directly related to the ventilation conditions, so is the materials LC50 value. The authors compiled toxicological data from a range of primary online databases and also requests were made to collect unpublished data that were not publically available. NO. J Ind Eng Chem 13(7):p11881194. Additionally, aromatic isocyanates with more steric hindrance are likely to be less reactive (such as the 2 position in 2,4-TDI (Fig. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. Cite this article. Privacy TDI is produced as the 2,4- and the 2,6- isomer which have a boiling point of 121C and 120C respectively. Fire and Polymers II: Materials and Tests for Hazard Prevention 599:p498517, Chun BH, Li X, Im EJ, Lee KH, Kim SH (2007) Comparison of Pyrolysis Kinetics between Rigid and Flexible Polyurethanes. 1986). A review by Paabo and Levin (1987) found that there is no difference in the decomposition products of rigid and flexible polyurethane foams at high temperatures regardless of their differing degradation mechanisms at lower temperatures. Thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) showed that the polyether based polyurethane began to decompose at 258C, with a second decomposition stage at 350C (which could be attributed to the fragmentation of the polyether polyol). 11) ultimately giving well-ventilated flaming. . Therefore, the products of decomposition can be predicted from the composition of the polymer. Neviaser and Gann (2004) compiled the toxic potency data for a range of materials including a number of fire retarded and non-fire retarded polyurethane foams. Suggested points of chain scission on a polyether polyol resulting in aldehydes, ketones and alkenes (Allan et al. This causes deterioration in mental and muscular performance. Equation Short chains with high functionality results in highly cross-linked polyurethane polymers which is characteristic of rigid foams. However there was significant scattering of the results with both high and low outliers (26mgg1 at 1.22 and 9mgg1 at 1.95). 4). Fire Hazards Of Polyurethane Foam - Klausbruckner Tests were carried out on the CMHR-PUF at 650C and 850C and at 700C for the PIR in order to achieve steady flaming conditions. Equation 2 calculates the FED of the major asphyxiants, CO and HCN, but without taking oxygen depletion or CO2 driven hyperventilation into account. Some methods have proved incapable of properlyreplicating the most toxic under-ventilated fire condition, where the yields of carbon monoxide and hydrogen cyanide are greatest, while other methods have shown good correlation with large scale test data. These reactions make up the basis of polyurethane chemistry and can be used to tailor polyurethanes with a range of properties by varying the structure and ratios of the individual components. Two mechanisms have been identified for the toxic effects of cyanide. The authors reported GC/MS analysis of the condensed phase products obtained. The authors would like to thank Dr. Linda Bengtstrom for her contribution regarding the toxicity of isocyanates. The results indicated that the formation of the precursor, TDI, was much faster and preferable to depolymerisation when the volatile compounds could escape. During polymerisation, isocyanates undergo a number of distinct reactions. The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. The effect of asphyxiants and deep lung irritants depend on the accumulated doses, i.e. Similarly to the trend reported by Stec and Hull (2011) in well-ventilated conditions, this can be attributed to gas phase free radical quenching in the material by the chlorine present in both the CMHR-PUF and PIR (2.53% and 3.56% chlorine by weight, respectively). They attributed the different decomposition mechanisms to the physical form of the polyurethane foam, rather than to any chemical differences. The presence of both amines and water in the decomposition products of polyurethane foams are discussed in later sections. Terence Richard Hull. This prompted the authors to perform further studies in order to understand why allowing the foam to smoulder increased the yield of HCN during flaming combustion. The yields of toxic products followed the expected trend of being higher in the under-ventilated conditions. However, in the field of combustion toxicity testing, this under-ventilated burning is the most difficult to create using bench-scale apparatus. These polyols will fragment and volatilise as the temperature increases, leaving behind a char (>600C). A "combustion modified high resilience" flexible polyurethane foam (CMHR-PUF) and a polyisocyanurate (PIR) foam were analysed a steady state tube furnace apparatus. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100250mgg1. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. Burning foam will emit mainly carbon monoxide, carbon dioxide and small traces of other toxic gases, such . There are two reasons for this: The yields of the major toxic products (carbon monoxide (CO) and hydrogen cyanide (HCN)from N containing materials) will be much greater. (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam. 13) (UK Fire Statistics 2013). This is due to the large range of available fire retardants found in polyurethane foams, which suggests that the toxicity will likely follow the general trends in the literature for all materials regarding fire retardants. The study also suggested that any remaining isocyanates residue would react with themselves to produce polycarbodiimides, thus anchoring the isocyanate precursors in the condensed phase until around 600C, where they would fragment. Early work by Voorhees (1975) identified what they described as extreme toxicity of the combustion products of a phosphate fire retarded polyurethane foam. This makes foam mattresses very harmful. These VOCs come mainly from the polyurethane used in the mattress, but also from other chemicals used in flame retardants and plastics, the researchers said. Investigator Chapters 1-5 --PART 1--Burns Flashcards | Quizlet For a fixed chamber volume (0.51m3), assuming complete combustion, the sample thickness will dictate the ventilation condition, thus a thin sample will burn under well-ventilated conditions with minimum toxic products, while a thicker sample might be expected to produce a high yield of CO and other products of incomplete combustion. However, no amines were detected in the vapour phase. 5-step decomposition mechanism for flexible polyurethane foam (Rogaume et al. Secondary air is added in a mixing chamber to give a total gas flow of 50Lmin1. (2011) Aerospace series - Burning behaviour of non-metallic materials under the influence of radiating heat and flames - Determination of gas components in the smoke; ABD 0031 Fire-Smoke-Toxicity (FST) Test Specification (Airbus Industries); Boeing BSS 7239, Test method for toxic gas generation by materials on combustion. HAZWOPER 40 - Lesson 3 - Toxicology Flashcards | Quizlet In air, the resulting decomposition fragments can be oxidised into CO, CO2, H2O and nitrogen oxides at high temperatures. TRH wrote the fire toxicity section of the manuscript. Taking into consideration the issues with repeatability of large-scale testing, the authors asserted that the similar trend in HCN yields supported the good relationship between the tube-furnace and large-scale results. (1981) reported similar data by analysing the inert-atmosphere pyrolysis of a series of biscarbamates to act as model compounds representing polyurethane foams. The protocol has been modified as a toxicity test by the mass transport industries, in the aircraft (EN 2826 2011), maritime (Fire Test Procedure Code 2010), and railway tests (CEN/TS 455452 2009). In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanide. Purser model, [AGI] is the concentration of inorganicacid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2]0.05. Babrauskas et al. Under well-ventilated flaming (<0.8), the yields of CO2 and NO2 were at their highest, while the yields of CO and HCN were at their lowest. The authors acknowledged that they did not include isocyanates in their calculations. The authors acknowledged that further investigation of the steady state tube furnace was warranted as in some of the testing they suspected an instrumental error, since they were unable to account for roughly two-thirds of the total carbon from the sample and detected unusually low levels of CO2 during the under-ventilated tests. The polyester fabric produced 9293mgg1 of CO when burned with very little difference in the flaming or non-flaming conditions. (1999) tested both rigid and flexible polyurethane foams using a bespoke smoke chamber apparatus to assess the toxicity of the flaming combustion products of the materials to rats. When the black char was burned at 600C, it yielded 14.95mg of HCN (65mg per gram of char) and the yellow oil yielded 21mg per gram of oil. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. CORE - Aggregating the world's open access research papers The main asphyxiants, carbon monoxide and hydrogen cyanide have been widely studied and are the best understood (ISO 13571 2007). Polyurethane foam, when burnt, gives off: Sulfuric acid Cyanide gas Ethane Phosphine. (such as polyurethane foam) burn slower (have a lower (HRR) than higher-density materials (cotton padding) of similar makeup. This makes the isocyanate functional group highly reactive towards nucleophiles with an available hydrogen. This step dramatically reduced fire deaths, which was considered a triumph at the time. What You Need to Know About Off-Gassing | Architectural Digest p 102-120. The authors also noted that the presence of aldehydes was detected during the flaming combustion of the flexible foam, albeit in extremely low yields. The danger of using urethane products is when the foam burns. When polyurethane foam insulation burns it gives off toxic gasses, very high temperatures and large amounts of thick, black smoke. Isocyanurate rings are the most thermally stable in an inert atmosphere and decompose between 270 and 300C. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. Therefore, in certain conditions, polyurethanes foams can reach their auto-ignition temperature and ignite which will significantlyalter the effect the decomposition mechanisms and resulting products. In a letter to the editor of the journal, Barbrauskas et al. Similarly, Busker et al. Rigid foam decomposed between 200 and 410C, while flexible foam decomposed between 150 to 500C. Their analysis indicated that, above 600C, the high temperature decomposition of MDI generated a large number of volatile fragments, including benzene, toluene, benzonitrile and toluonitrile. The first being a depolymerisation which would dissociate the polymer to isocyanates and alcohols, the second being dissociation to a primary amine, an olefin and carbon dioxide. Aromatic isocyanates are more reactive than aliphatic isocyanates due to the electronic effects of the aromatic ring. Fire retardants, such as gas-phase free radical quenchers, have been reported to increase the yields of CO in well-ventilated conditions by preventing the oxidation of CO to CO2. Polyurethane foam when burned gives off - wiehoch.com DiNenno et al., eds.). Similarly, the polyether based foam produced 15.1mgg1 to 28.1mgg1. To a lesser extent, parameters such as temperature and oxygen concentration also affect the yields of toxic products. Further to this, a similar pattern began to emerge in the injuries of fire victims (Fig. Rubber Chemistry and Technology 32(2):p337345, Article Equation3 uses a similar principle to equation1 to estimate the combined effect of all irritant gases. Acrolein and formaldehyde are formed especially from cellulosic materials under non-flaming decomposition conditions, but products of vitiated combustion contain other organic irritants. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The PIR foam produced similar HCN yields to the CMHR-PUF until 1.5, after which it increased more rapidly to give a yield of 20mgg1 at ~1.75.
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