Section 2 Definitions

2.1 Materials

2.1.1 Non-combustible material means a material which neither burns nor gives off flammable vapours in sufficient quantity for self-ignition when heated to approximately 750°C, according to an established test procedure. Any other material is a ‘combustible material’.

2.2 Fire test

2.2.1 A Standard Fire Test is one in which specimens of the relevant bulkheads or decks are exposed in a test furnace to temperatures corresponding approximately to the standard time-temperature curve. The specimen is to have an exposed surface of not less than 4,65 m² and height (or length of deck) of 2,44 m resembling as closely as possible the intended construction and including where appropriate at least one joint. The standard time-temperature curve is defined by a smooth curve drawn through the following temperature points measured above the initial furnace temperature:

At the end of the first 5 minutes, 556°C
At the end of the first 10 minutes, 659°C
At the end of the first 15 minutes, 718°C
At the end of the first 30 minutes, 821°C
At the end of the first 60 minutes, 925°C

2.2.2 The fire behaviour of the chamber equipment is to be checked by reference to the relevant test certificates and symbols, as applicable.

2.2.3 A check is to be made as to whether the electrical heating systems and heaters are fitted with protection against overheating.

2.2.4 Fire alarm, detection and extinguishing appliances are to be subjected to a functional test.

2.3 Flame spread

2.3.1 Low flame spread means that the surface thus described will adequately restrict the spread of flame, having regard to the risk of fire in the spaces concerned, this being determined by achieving a Class 1 result when tested in accordance with BS 476:Pt. 7.

2.4 Fire retardant characteristics

2.4.1 Fire retardant characteristics are possessed by materials which do not flame significantly nor sustain combustion in compressed air at a pressure of 6 bar after the removal of a test flame, this being determined by an acceptable test procedure.

2.5 Divisions and spaces

2.5.1 ‘A Class divisions’ are those divisions formed by bulkheads and decks which comply with the following:

They are to be constructed of steel or other equivalent material;
They are to be suitably stiffened;
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 standard fire test;

They are to be insulated with approved non- combustible materials, such that the average temperature of the unexposed side will not rise more than 139°C above the original temperature, nor will the temperature, at any point, including any joint, rise more than 180°C above the original temperature, within the time listed below:

Class ‘A-60’	60 minutes
Class ‘A-30’	30 minutes
Class ‘A-15’	15 minutes
Class ‘A-0’	0 minutes

A test of a prototype bulkhead or deck may be required to ensure that it meets the above requirements for integrity and temperature rise.

2.5.2 Non-load bearing divisions equivalent to ‘A Class’ are those divisions formed by fire walls or decks which comply with the following:

They are to be constructed of steel or other equivalent material;
They are to have sufficient strength for the intended purpose;
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 standard fire test;
They are to be insulated with approved non- combustible materials such that the temperature rise criteria stated in Pt 5, Ch 8, 2.5 Divisions and spaces 2.5.1 are not exceeded;
They are to be satisfactorily connected to supporting structural members which are capable of carrying all concentrations of loads to which they may foreseeably be subjected;
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.

2.5.3 Oxygen enriched atmospheres are those atmospheres in which the concentration of oxygen exceeds 23 per cent by volume or the partial pressure of oxygen exceeds 160 Torr (mm Hg) or both.

2.5.4 Diving control rooms are those spaces in which the control equipment necessary for safe performance of diving operations is centralized.

2.5.5 Enclosed spaces for diving systems or parts thereof are to be provided with a forced ventilation system capable of effecting at least 8 changes of air per hours. The air must be drawn from an area not subject to an explosion hazard.

2.5.6 Diving systems on ships and other floating structures may only be installed and operated in areas not subject to an explosion hazard.

2.6 General Fire Precautions

2.6.1 Any equipment requiring lubrication inside the chamber should be lubricated with a suitable oxygen-compatible lubricant approved for the purpose. Mineral oil or grease in an oxygen environment may cause a fire or explosion. Items introduced into the system containing mineral based oils or greases may also, under certain conditions, create an explosion when mixed with oxygen. For example, wheel chairs with greased wheel bearings. A variety of suitable and approved lubricants will be required for the differing applications within the chamber.

2.6.2 Flammable gases must be stored separately to oxygen and oxidising gases, and not in the chamber enclosure. The use of flammable agents inside a hyperbaric facility, or in proximity to any air intake, should be forbidden. Gas burners and lighters should not be permitted in the chamber area.

2.6.3 It is essential that all areas of the hyperbaric chamber, and the associated plant, are kept free of grease, lint, dirt and dust. A regular cleaning programme should be introduced and maintained. Those responsible for cleaning must be given the appropriate induction training. The chamber facility manager must approve cleaning materials.