O Aljumaiah

Air Starved Wood Crib Compartment Fire Heat Release and Toxic Gas Yields

Pine wood crib fires (4.6 kg) were investigated in a 1.6 m fire compartment with air ventilation between 3 and 40 air changes per hour (ACH). The cribs were 380 mm tall and 300 mm square. The fires rapidly self extinguished at 3ACH and struggled to continue to propagate at 5 ACH, where only 15 % of the initial crib mass was burnt. For 11, 21 and 37 ACH the cribs burned completely and the oxygen consumption HRR increased with ventilation. All three fully burned fires had rich equivalence ratios for most of the fire duration and associated high CO yields. Extremely toxic levels of CO, acrolein, formaldehyde and benzene were generated and the total toxic N on an LC50 basis was over 30. The combustion efficiency was very low due to the very high CO and total hydrocarbon emissions and this led to a major difference in the HRR by mass loss and that by oxygen consumption. The results demonstrate the severe toxic conditions that occur in ventilation restricted fires with wood as the main fire load.

Wood Crib Fires under High Temperature Low Oxygen Conditions

wood crib fires were investigated in a compartment fire under post-flashover conditions using a natural gas (NG) burner to rapidly generate 500 o C furnace temperature and oxygen levels of 12%. The subsequent fire temperatures were 600-700 o C, with oxygen levels below 5%. These conditions reproduce the circumstances in developed, under-ventilated fires inside a hot compartment where yet uninvolved material is available for combustion. Two pine crib fires were investigated: a 3 kg crib which resulted in lean overall combustion and a 9 kg crib that resulted in rich overall combustion. For the low fire load lean combustion case, the combustion efficiency was high and the yield of toxic products was low. However, for the high fire load with rich combustion the wood was mainly gasified and the combustion efficiency was very low. An extreme fire toxicity condition, as well as the circumstances for back- draft explosions, was generated in this post-flashover rich combustion case.

PVC Cable Fire Toxicity Using the Cone Calorimeter

Electrical cables with PVC sheaths were investigated for their ignition characteristics, heat release and toxic yields using the cone calorimeter. 40 KW/m2 was required to get a significant heat release for PVC. A heated Temet Gasmet FTIR was used for the toxic gas analysis. Gas samples were taken from the cone calorimeter-diluted exhaust duct and transferred to the FTIR using a 190 °C heated sample line, heated pump and filter and a second 190 °C heated sample line between the pump and the FTIR. The FTIR measurement zone was also heated at 190 °C so that no loss of HCl and other condensable gases occurred. This heated sample system enabled the theoretical HCl yield, based on the chlorine content of PVC, to be measured. This indicated that there were no other significant chlorine products in the well-ventilated fires. A peak yield of 0.45 for HCl was found. There were significant yields of the irritant gas acrolein and formaldehyde, and acrolein was the most important toxic gas. The PVC sample and the char that remained after the test were analysed using TGA, and the results showed that only 41.6 % of the chlorine in the sample was lost as HCl in the cone calorimeter test, the rest remained in the char.

Toxic Gas Emissions from a Timber-Pallet-Stack Fire in a Full-Scale Compartment

A stack of wooden pallets was burnt in a 41 m3 room with air supplied via the door connected to a 3.5 m-long corridor, the only air supply path to the room. Combustion emissions were sampled from within the fire room and analysed using a heated Fourier transform infrared (FTIR) analyser, via a heated sampling system. Development of the fire was also captured photographically and presented here with associated measured fire characteristics. Detailed full-scale compartment fire characteristic measurements are provided including source fuel composition, temperature gradient at different locations, mass loss rate, heat release rate, calculated equivalence ratio and measured toxic emission yields. Yield measurements are presented as a function of the equivalence ratio. These measurements are useful for fire investigation and fire modelling purposes. Carbon monoxide yields approaching 0.3 g/g were much higher than those currently recommended for fire modelling. Acrolein and total hydrocarbon yields were in good agreement with other tests in the literature.