Fire relief sizing of tanks (HAZOP reccommendation)

[smollett]

We have gone through a HAZOP and one recommendation that keeps cropping up is sizing of tanks for fire relief. I can understand these for chemical tanks in areas where fire is concievable but we have recommendations to carry out fire relief case on bilge holding tanks and fresh water tanks. The size of these tanks and their location mean that any temperature rise of tank contents is likely to be very slow in the event of fire. Vents are currently sized to class rules which state 1.25 times combined inlet areas. There is no mention in class rules of sizing these tanks for fire relief but how can I challenge this reccommendation?
Thanks