Advantages: simply evaluation of compliance with established requirements; no requirements for high level of naval architect expertise。

Disadvantages: requirements specified without a clearly statement of objectives; no promotion of cost-effective designs; very little flexibility for innovation。

Performance codes

Advantages: establishment of clear safety goals and leaving the means of achieving; permitting innovative design solutions that meet the performance requirements during first stages of application; facilitating use of new knowledge when available; allowance for cost- effectiveness and flexibility in design。

Disadvantages: difficult to define quantitative levels of safety performance with those goals to the designer criteria; need for education because of lack of understanding especially; difficult to evaluate compliance with established requirements; need for validation of the tools used for quantification。

It is then possible to give some examples whose performance codes application can give advantages:

large passengers (cruise) and ferry  ships passive fire protection (walls and ceilings) can be moved in order to create larger connected areas;

in large ships higher passive resistance can substitute fixed installed fire suppression measure;

in naval ships the expected extent of damage can be reduced through improved fire measures。

The Possible Alternative Methodology

Background

Probably it is not opportune to explicate in a few spaces the contents of an ambitious work; it is also possible to rearrange the contents of the IMO documents in three essential points:

-to inpiduate models that calculate opportunely characteristics in a compartment or groups of compartments ;

-to define accidental scenarios (in agreement mainly with the classification societies) on which develop fire events evolution;

-to evaluate objectifies and consequences of a fire event in relation to the chosen scenario and measure of the presumable safety level。

The supposition of performed-based design is that the fire is a phenomenon (physical and chemical) that, for when complex, it is possible to be reconstruct with conformed models。

It is then possible, at least, to outline two possible applications:

-possibility to valuing derogations。 The hypothesis of adopting a measure in place of other will be possible to weighing criterion objectives;

-to assess emergency plans; it is possible follow the trend of a fire and the propagation of combustion product, to know, instant for instant, the survival percentage of a person in an environment;

Some Models

The models, generally, are much more economic than the tests (full scale or little scale)。 The simulation models  represent  the  fire  compartment  evolution with

different initial situations。 It is useful mainly for estimating the criterion of supportability, and for the likelihood of fire propagation toward other compartments。

In particular, it is possible to subpide the models mainly in two categories:

zone models field models

Zone Models

A zone model calculates the conditions that are determined in the environment, piding every compartment in two homogeneous zones。

The superior, of the smokes and gases where are present the products of the combustion。 The other is the lower zone, free of smoke and fresher than those superior。

The heights between the “two zones” change with the development of the fire。

The zone models estimate against the time:

-the temperature (average) of the lower  and superior layers (upper and lower layers temperature);

-the position of the interface  among zones (interface height);

-the oxygen concentration (O2 faction);