Tell about class bulkhead.

               A-Class bulkhead:   

1.     Constructed with steel or equivalent material.

2.     Suitable stiffened.

3.     Prevent the passage of smoke or flame for one hour standard fire test.

4.     Temp. should not rise, A-60, 60 min, A-30, 30 min, A-15, 15 min, A-0, 0 mins. 

B-Class bulkhead:

1.     Constructed to prevent passage of flame for a half hour standard fire test. 

2.     Temp. should not rise, B-15, 15 min, B-0, 0 mins. 

C-Class bulkhead:

1.   Made of non-combustible material, but meet no other requirement.