A bench-scale experimental setup has been used to study the conditions necessary

for smouldering ignition in four types of loose-fill wood fibre thermal insulation, and

to study the development of the smouldering process. The products varied with regard to

wood species, grain size and fire retardant chemical additives. The test material was

placed in an insulated open top container and heated from below. Temperatures within

the sample and mass loss were measured during the tests. Both the fibre size and the level

of added fire retardant seem to influence the smouldering ignition. Two different types of

smouldering were identified in this study. Materials undergoing smouldering Type 1

obtained maximum temperatures in the range 380C to 440C and a total mass loss of

40 wt% to 50 wt%. Materials undergoing smouldering Type 2 obtained maximum temperatures

in the range 660C to 700C and a total mass loss of 80 wt% to 90 wt%. This

implies that Type 2 smouldering involves secondary char oxidation, which represents a

risk for transition to flaming combustion and thereby a considerable fire hazard. This has

been an exploratory project and the results must therefore be considered as indicative.

The findings may, however, have implications for fire safety in the practical use of loosefill

wood fibre insulation in buildings, and further experimental studies should be performed

with this in mind to obtain more knowledge about the topic.