94 ◾ Risk Assessment and Security
4. Class D, res involving certain combustible metals (magnesium, titanium,
zirconium, sodium, potassium, etc.) requiring a heat-absorbing extinguishing
medium not reactive with burning metals
5. Class K, res in cooking appliances that involve combustible cooking media
e NFPA 20113 (2012a) explained that ash re may occur in an environment
where fuel and air are mixed to combust with a heat ux approximately 84 kW/m
2
.
e majority of road tunnels of signicant length have some form of ventilation
system for various reasons including smoke control in a re emergency (Carvel
et al. 2009). ese fall broadly into two categories—transverse systems and lon-
gitudinal systems—although an increasing number of tu ...