I am trying to decide how to calculate the probability of fire starting in the room and what is the probability of fire spreading to other equipments in the room. Is there any data I can refer to for probability of fire with regards to occupancy/equipment type ?. There is a table in PD 7974-7 Annex B which gives an over all probability of fire starting in various types of occupancy, but when assessing each room individually I am not able to find any data. Any other suggestions are welcome.
x = Probability of fire starting
a= Probability of fire spereading to other equipment
b= Probability of fire spreading to all room area
c= probability of fire spreading to outside the room
Thank you.
"Probabilities" are always elusive, fluid, and relative things! They can only provide some estimation of relative risk, but as with all statistics, only apply to the population, and not the individual. More factors to consider in such calculations can be found in "NFPA 5000 BuildingConstructionAndSafetyCode" standard and its references.
In general, the range of probabilities for an individual room can range from 0-100%! One way to approach safety from a risk perspective is to start from either end, and then add or subtract factors until an “acceptable” value is achieved. Industrially, “0” fires are acceptable, so in addition to engineering and procedural safeguards, sufficient mitigation measures are also included in the design and construction of facilities.
Fundamentally, everything is dependent on the “Fire Triangle” - Energy, Oxidant, Flammable Material. Eliminate any ONE of them, and you don’t get a fire. Each “side” of the triangle is essentially a continuous range, and the combinations (essentially infinite) are the relative probabilities of the occurrence of a fire.
The probability of fire starting is a compound phenomenon. You need to know
· Probability of existence of combustible material- it is zero if there is no combustible material and 1 for an ordinary residential building if there are books and clothing items.
· Ignition sources and probability of igniting the combustible material. If there is no ignition source the probability of a fire is zero. For this reason, sources of heat are separated by firewalls. For example, the kitchen should have a fire-resistant door and be shut all the time. However, there is a possibility of starting of fire from the light fittings
· Probability of air circulation. For the ordinary residential building this probability of one.
The probability of fire spreading depends on the existence of enough air, combustible materials, open communication between rooms, and the probability of failure to suppress the fire.
This means you need a specific case to answer your question. There is no general answer.
The most common ignition sources in fires are: flames, heated surfaces, sparks, sparks and electric arcs (in addition to lightning, which are a natural source of ignition). Fuel + Oxidant = Light + Heat + Smoke, Ash, Gas, etc.
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