The Toxicity of Fire in Building Insulation Materials

The article, “Assessment of the fire toxicity of building insulation materials,” by Stec & Hull (2011) reveals that a wide variety of materials and methodologies for the insulation of buildings are used to suit different circumstances. Reflective panels play an essential role in reducing the radiative heat transfer for larger temperature gradients. This information indicates that the most efficient and expensive form of insulation is the vacuum. From this view, gases have low thermal conductivity but they have the capability to allow convective heat transfer. The effectiveness of gas insulation is evident in a situation where gases are trapped in a matrix with the objective of preventing convection. Fire safety measures for buildings are categorized as flammability and fire toxicity. It is evident that fire hazard evaluation requires consideration of various aspects present in the fire. For instance, there is a need for examining the most probable fire scenarios and the prediction of the rate of fire growth as well as the amount of fuel present and its effect on the occupants and their ability to escape safely. Toxicity product yields depend on the composition of the materials and fire conditions. The flaming combustion fuel/air ratio has the highest yield than non-flaming combustion. Inhalation of toxic gases also becomes an effective activity contributing to the deaths of people in a community. Replacement of prescriptive standards by performance-based fire codes requires assessment by fire safety engineers, which includes prediction of the toxic product distribution within the building from a fire. Prediction of toxic fire hazard depends on two parameters: Time concentration profiles for major products depending on the fire growth curve and the yields of toxic products; and toxicity of the products, based on estimates of doses likely to impair escape efficiency, cause incapacitation, or death. Fire gases contain a mixture of both oxidized and unoxidized products. For instance, there exist different gasses such as carbon dioxide (CO2) while partially oxidized products include carbon monoxide (CO), and hydrogen cyanide (HCN) or aldehydes (Stec & Hull, 2011). The partially oxidized products are responsible for causing deaths associated with such gasses. In an attempt of putting off fire, Carbon dioxide and hydrogen cyanide are some of the critical gasses applied in the process as they prevent the uptake of oxygen. The presence of CO2 in blood, which stimulates hyperventilation, increases the respiration rate and hence the hazard from the toxic components of the fire gas. 

Fire toxicity is one of the crucial elements that should be considered in fire risk assessment process. The toxic products of some materials vary depending on the ventilation condition. This information indicates that it is crucial for firefighters to access fire toxicity under the more dangerous, especially under ventilated burning conditions. The ISO TS 19700 steady state tube furnace is an essential tool for undertaking conducting and understanding such assessments. The gap between traditional and modern studies originates from the fact that the former was conducted under-ventilated conditions and the inconsistency in methodology made it difficult to effectively measure toxicity to real fire conditions. Despite the existence of this difference, both studies indicated an increase in fire toxicity from glass wool and stone wool to polyurethane foam. The current work supports the idea that lower carbon monoxide yields for all materials under well-ventilated conditions, compared to under-ventilated conditions, although the presence of halogens increases the level of carbon monoxide in well-ventilated conditions. 

References  

Stec & Hull (2011). Assessment of the fire toxicity of building insulation materials.  Energy and Buildings ,  43 (2-3), 498-506.