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 3 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 LC 50 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.