‘H’ Class Divisions (fire divisions)
‘H’ Class divisions are those divisions formed by fire walls and decks which comply with the construction and integrity requirements for ‘A’ Class divisions, 2.6.1(a) and (b) and with the following:
(a) They are to be so constructed as to be capable of preventing the passage of smoke and flame up to the end of the one hour hydrocarbon fire test. (Note that some administrations may require the ‘H’ Class division integrity to be maintained for 120 minutes).
(b) They are to be insulated with approved non-combustible materials such that the average temperature, on the unexposed side, when exposed to a hydrocarbon fire test, will not rise more than 140°C above the original temperature, nor will the temperature at any one point, including any joint, rise more than 180°C above the original temperature within the time listed below:
Class ‘H-120’ – 120 minutes
Class ‘H-60’ – 60 minutes
Class ‘H-0’ – 0 minutes.
(c) A test of a prototype fire wall or deck may be required to ensure that it meets the above requirements for integrity and temperature rise.
Source: Rules and Regulations for the Classification of Mobile Offshore Units, Part 7, Safety Systems, Hazardous Areas and Fire, June 2013, Lloyd’s Register, Global Standards