Investigation of Air Starved Fire Using Cone Calorimeter - Case Study Example

Name : xxxxxx Tutor : xxxxxx Title : Fire Report Course : xxxxxx Institution : xxxxxx @ 2010 Fire Report The casualty that occurred as a consequence of fire in Edinburgh within hospital that left more than 10 dead was as result of the emission of toxic gases though the fire had not fully spread from the store room. Great toxicity is shown by Acrolein and the formaldehyde compared to CO in a situation whereby fire has caused air starvation and both are effects from pool fires as well as from wood fires (Andrews et al., 2000). The situation in Edinburgh gave birth to new curiosity related to fire gas products which are extremely lethal in cases where there are favorable statuses for air starvation.  A burning substance does not only produce smoke which possibly will make occupants of a certain apartment fail to have the visibility; but it also results in respiratory tribulations which are a nuisance. CO and HCN are the most evident yield of fire and their quantity is usually determined by thermal disintegration constituted by the load of the fire which is dictated by the supply of the oxygen as well as the available temperatures.  The N-Gases which is in  a form of a model consist of ratios which are measured in regard to the concentration the toxic gases which are seven in relation to the lethal concentration (LC50) which results to more than 50 percent of death of animals in a given test. The N-gas value is more often than not found out by the summing up of the seven relative toxicity terms of the gases. Even so, the toxic gas emission HCN is typically low except in cases where the load of the fire poses such natural compounds like the Nitrogen (N), Chlorine (CL) as well as the Bromine (Br) compound. Due to the fact that there are few types of equipment put in place to ensure effective measurement of the acidic gases as well as the irritant ones, there is the need to use the Fourier Transform Infra-Red spectroscopy (FTIR) to be used in investigating the impact of these gases (Andrews et al., 2000). The odorless gas which is also colorless carbon monoxide, does not sufficiently show the signs of the toxic gases as the victims who survive the occurrences narrate.  Most scientists have distinguished that fires which happen in enclosed apartments with door closed have unlike air starvation from those which occur in apartments with door open. Past experiments show that the all time richest equivalent ratio which had air changes stated at 2.7 was 0.55 as well as an hour having the ratio of 0.8 which corresponded to 30 air changes. When temperatures are quite low they are unable to the expected oxidation of any unburned fuel (UHC) or even the carbon monoxide (CO). The low level of HCN which is also toxic mainly resulted from reactions of hydrocarbons with nitrogen which forms the rich part in air (Andrews et al., 2000). Evaluating the general toxicity in any fire is very difficult due to the many toxic products produced at once. Within the same model, toxic gases being mixed and in comparison to being additive was greatly advocated based on an approach that put in to consideration concentration multiplied with time  using a maximum tolerable exposure of five minutes other than the traditional use of the lethal concentration 50 (LC50). Alternatively, this model leaves behind much issue on whether death measurements can de used to exactly indicate a toxic level that can suitably and objectively save people from fire menace. The lethal concentration 50 (LC50) measurements in this N-gas model are few and generally constitute insufficient toxicity assessment results in situations where all toxic gases which were significant were not included. The mixture of toxic gases resulted in developing the concept of Fractional Irritant Concentration (FIC) which puts in to deliberation the assessment of effects of irritants in cases were they have combined.   As the name of this development indicates, every irritant concentration is usually given in form of a fraction in relation to other concentrations of all the irritants in a given instance. The total concentration of the irritants is given by summing up all the fractions of each independent irritant in the occurrence. When the concentration of the irritants is equal to one, it is a clear indication that escaping for safety is almost impossible because it shows that the irritant caused by the smoke is very high for any one to escape. When the concentration of the irritants is equal to 4 it is more dangerous than when it is equal to one since in this instance there is no probability of escaping for safety is zero. The assessment of the relative toxicity level of CO as well as of that of HCN using a method based on COSHH is no different from the relative toxicity level shown when the assessment is carried out with the lethal concentration 50 (LC50).  However, there are significant discrepancies especially in irritants as well as acidic gases areas such as acetic acrolein, the from the occupational exposure data brought about by comparing the gases (Andrews et al., 2000). The lethal concentration (LC50) many times generally deals with gases of higher concentration than that of carbon monoxide while the exposure data on occupational bases deals with gases of concentration which is lower than that of carbon monoxide for the same hazardous exposure. This argument of concentration brings notable dissimilarities linking the exposure data that is based on occupational grounds and the lethal concentration 50 (LC50). For effective measurements dealing with the levels of toxicity of gas products which comes from fire, there is a great need of resolving this difference that between the lethal concentration 50 and the occupational exposure data. If the conflict is not solved, there are likely to be a lot of erroneous assumptions, like the assumption that the COSHH data is the correct when it was used to give relative toxicity level of acidic and toxic gases. One of the scientists showed the evidence about the experimental fire from a ventilated area and concluded that the data demonstrated an inclusion with a door open (Andrews et al., 2000). The introduction of Kin as an exposure to air restriction was later put in to action, which indicates a leakage of the air that is usually equivalent to that in an open area and with Av as initials, and should be at odds with the cross sectional part of the cubic space of a degree that is corresponding to the test room. This implementation allows the assessment of air leakage for any kind of room. According to research, standards put in to place to see that smoke if fully controlled, mainly have permissible gaps which convert to a Kin of 0.05 percent any room whether be it an hotel room or a domestic one, that is able to result to a 9 air changes per hour.   A closed door can achieve a Kin of 0.5 percent smoke leakage which is the highest in the event that the door is a shaft one, though rarely do people use shaft doors. Commonly, many times half the area that is under experiment would be prone to air in-leakage since the fire products mostly leak to the upper part. This means that when the ventilation is low, the air changes can be more than 4 per hour. Very little study has been done on this kind of fires despite the fact that they are the fires that the passive protection measures have tried to see that they occur. In cases of a room with door fully open has a Kin of more than 17 percent and if the window is open the Kin is of more than 5 percent. Most investigators who carry out investigations related to fire occurrences from apartments with the door and window open scenarios (Andrews et al., 2000). Air starved fires are usually subjected by little fire hotness with a Kin having a percentage that is less than 1 for carbon monoxide and UHC thus resulting to inefficient combustion thus leading to disequilibrium of the considerations of carbon monoxide. Another prevailing reason as to why scientists, who are specialist in fire engineering, investigate fire in enclosed areas by making the supply of air to be fixed is because by doing so they directly simulate as well as having aircraft the interior fire. Closing of doors in any aircraft definitely leads to a closed volume. The supply of the air to the aeroplane is usually taken from the compressor on the engines after which it is cooled down and later transferred to the inner of the plane thus enabling the passengers in the plane to stay alive. Dimensions related to smoke most of the times are done using the optical obscuration and while the mass of the soot usually go through the conversion from the obscuration and the correlations of performing the conversions are regarded as being dubious. The concerns of the particles in the air are as a result of their toxicity (Andrews et al., 2000). Fires generate fine particle which have higher concentration than the particles in the atmosphere and this means that deaths are very evident from particulates in air starved fires in event that people become incapacitated by the particles. When the fire products finally cool down, the fire particles form a nucleus through condensation for hydrocarbons. The door was made of glass and was air sealed with high temperatures the purpose of the glass door being to monitor the early phase of the fire. The unchanged door was also fitted with an insulation that had a thickness of more than 20 mm on the outer side of the door. This kind of lagging usually helps in putting a stop to cases of rays that may result from the fire. The load of the fire is regularly placed at the central point which is mainly supported by three legs that are connected to the three legs of the load cells within the plenum of the air underneath the chamber of air. By doing so it ensured that load cells were fully kept cool and this gave room for the determination of the rate of fire burning mass. A thermal heap flow meter is the channel through which the air was fed to the compressor into the area of the fire through the plenum.  A research on fire issues that is developed slowly over few minutes had a spectrum with average time and was used to resolve the toxic gases which are dictated by time when fire breaks up (Andrews et al., 2000). The Temet FTIR has a resolution which is quite typical of 3 ppm with a percentage of 2 as accuracy as well as having a percentage of 0.01 as the precision of the range of the measurement. The calibration of the FTIR is in such a way that it can detect more than 65 species at the same time. In this experiment majority of the analyzed gases were found to be hydrocarbons though most of them are not toxic. The calibration of the FTIR is usually done by the manufactures of the same device using their own gas reference concentrations in connection with all the present species in the exhaust samples present. The fire configurations of the experiment include the pine wood as well as the cotton towel. The wood and the cotton have similar composition since both have the requirements of air which are stoichiometric. The ventilation rates for the fires ranged from 1.0 to about 40 changes of air per hour. The comparison of wood crib with diesel as well as with kerosene fires at 2.7 changes of air per hour configuration was done in the previous work. A ventilation rate is equal to one change of air per hour in the closed room which contains doors that limit the emission of smoke as well as the air entrance. For the same experiment to progress with high changes of air close to 10 per hour, the doors need to some extent be opened while in the situation whereby the changes of air are above 40 per hour the doors should be opened (Andrews et al., 2000). According to scientists fires which were controlled by ventilation entrained their own air through openings which had high restrictions, after the first phase of burning the air in the closed area which constituted a steady burning rate as well as the air consumption. The fires from cotton at the maximum point of heat release had a mixture of carbon monoxide and HC which their emission reduced with increasing rate of ventilation and this was a consequence of the equivalence ratio within the fires of the globe being lean though richer hence increasing the overall efficiency of combustion. Fires from the cotton material which had low temperatures resulted in low NOx this was due to low emissions oat the smouldering fire phase of the cotton towel. Despite the fact that the global equivalence ratio of the fire is always lean, the emissions of carbon monoxide and HC from the fire loads of cotton and pine cribs were reducing with increasing ventilation which gave birth to increasing rates of oxidation. In spite of the fact that the two fire loads had notable similarities in cases where the ventilation rates were high, the fire from pine cribs produced carbon monoxide and HC with higher levels than those of cotton at lower ventilation rates within the phases of the fire of the two loads. FTIR Analysis of the Main Toxic Gases This analysis shows that ventilation has great influence on the emission of gas products of acrolein as well as the formaldehyde. It indicates that the emissions were highest at high ventilation rates in the phase where there low levels of oxygen (Andrews et al., 2000). In cases of low rates of ventilation, the gases were low in the peak of the heat region though it was high in the combustion phase. The two different phases of fire wee used in illustrating different levels of the toxic gases over a range of compounds. Conclusion   The air starved fires have high levels toxic yields. The perishing of more than 14 persons in Edinburgh could have been as a result of low rates of ventilation from both the pine cribs as well as the cotton towels which have high levels of toxicity after combustion (Andrews et al., 2000). It is also clear that there is a lot of believe on using the COSHH assessment method more than the way the lethal concentration is used due to the fact that it is a recognised statutory in united kingdom. It is evident that toxic products of different fires increased to a maximum point of intensity in connection with the ventilation more often at 10.0 air changes per hour. Cotton fires were similar to those of woods in though they had lower toxicity level. Finally the assessment method using the COSHH 15 minutes to indicate the level of toxicity showed acrolein to be the most common toxic product for all types of fires while the lethal concentration showed that carbon monoxide was the most common toxic product in all situations. References 1. Andrews, G.E., Daham, B., Mmolawa, M.D., Boulter,  S., Mitchell, J., Burrell, G., G unamusa,W. and H.N.    Phylaktou. 2005. Toxic Emissions from Air Starved Fires. Proc. 8th International Symposium on Fire Safety Science, Association for Fire Safety Science. 2.    Purser, D.A., 2002 3rd Ed. ‘Toxic assessment of combustion products’, In: Dinenno, P.J. (Ed.), SFPE Handbook of   Fire Protection Engineering. 3.      Hartzell, G.E., 2001 ‘Engineering analysis of hazard to life safety in fires: the fire effluent toxicity component’, Safety Science. 4.             Andrews, G.E., Li, H., Hunt, A., Hughes, D., Bond, S., Tucker, P., Akram, S. and Phylaktou, H.N., 2007 ‘Toxic Gases in simulated aircraft interior fires using FTIR   analysis’. Proc. 5th International Colloquia on Explosions in Reactive Systems, Edinburgh. 5.             Andrews, G.E., Ledger, J. and Phylaktou, H.N. 1999  ‘Enclosed pool fire flame temperatures and global heat loss using gas analysis’, Sixth International Symposium on Fire Safety Science. 6.             Andrews, G.E., Ledger, J. and Phylaktou, H.N., ‘Pool   2000. Fires in a low ventilation enclosure’, I.Chem.E. Symposium on Hazards XV, ChemE Symposium. 7.             Andrews, G.E., Ledger, J. and Phylaktou, H.N. 2000 ‘The Gravimetric Determination of Soot Yields in Enclosed Pool Fires’, Proc. 3rd  International Colloquia on Explosions in Reactive Systems, Windermere. 8.  Gottuk, D.T., Roby, R.J. and Beyler, C.I., 1992. A study of carbon monoxide and smoke yields from compartment fires with external burning’, 24th Symposium (International) on Combustion. 9.          Kauppinen, J.K. et al., 1995. Carousel Interferometer, Applied Optics, 10.          Saarinen, P. and Kauppinen, J.1991. Multicomponent analysis of FTIR Spectra, Applied Spectroscopy. 11.          Control of Substances Hazardous to Health   Regulations, EH40/2005 Workplace exposure limits, HSE Books, UK    Health and Safety Executive. Read More