-the monoxide carbon concentration(CO2  faction);

-the visibility;

-the flow in entry and in way out for opening toward the outside or toward other locals。

Such informations are essential to estimate the supportability conditions of a compartment or to determine if it is possible to verify the flashover。

Field models

The field models estimate the evolution of the fire in a space by mean numerical tools, resolving the conservation equation of mass, the energy, etc, which result from a fire evolution。

This approach is developed mainly by means the finite element method, already used in other sectors。

The field models, then, pide a space in an element of elevated numbers and resolve the conservation equation in each of them (greater the elements number, more detailed will be the solution)。 The resulted are three- dimensional effects and, if compared with the zone models, are much more detailed。

The adaptability of the existing models can be obtained to five possible cases:

1)The fire safety assessment in a propulsion plan。

2)The fire safety assessment in a passenger cabin or more cabins;

3)The fire safety assessment in a passenger ship theatre or movie theatre;

4)The fire safety assessment in a Ro-Ro passenger ship passengers deck;

5)The fire safety assessment in a Ro-Ro passenger ship vehicle deck。

It is important underline, besides, that the utilization of these methods doesn't contrast with the survival of the prescriptive approach。

Some Examples of Performance Design Criteria

The design of fire protection systems in compartments of ships, using engineering calculations, should be accomplished following deterministic or probabilistic techniques, or both。 Usually, deterministic methods can be used for calculating fire growth, smoke spread, and evacuation analysis。 The results of these calculations should be then compared to established deterministic criteria to determine whether the design is acceptable。 Probabilistic methods should be also used, and the end result should be presented in terms of life or property risk levels for a “part” of ship and their occupancy。 In this case, the performance criteria should be also given in terms of acceptable risk levels, which are referred to as probabilistic criteria。 Both deterministic and probabilistic criteria mast be subordinate to SOLAS 2000 and/or higher standards of the national flag administration bodies。

Deterministic criteria

Deterministic calculations provide quantification of fire

The data shown in Tables 1 should be used to determine the ignition of the first item and subsequent items (materials) close by。

Therefore, one way to minimize ignition is to ensure that the heat sources that may be present in a compartment cannot radiate enough heat to cause ignition of the combustible materials in that compartment。

Fire growth criteria

Following ignition, the rate of fire growth is one of the most important parameters used to determine the assessment of a fire safety design。 The rate of fire growth can be determined using experimental results, computer models or empirical correlations。

One of the most practically used method is the t-squared fires method, in which the heat release rate, Q, is assumed to continuously grow quadratically as a function of time, t, until either the combustible is totally consumed or the heat release rate is assumed to have reached a peak value。 In formula, the fire growth rate curve can be written as:

processes such as fire growth, fire and smoke spread, evacuation time on parts of ship or its passengers。 Normally, these criteria have to be met under   probable

Q k t 2

The k values are evaluate for:

(1)

worst-case     scenarios。     The     deterministic   criteria