How is a fire risk assessment carried out?
How is a fire risk assessment carried out?
Carrying out a fire risk assessment
As for buildings, as part of carrying out a fire risk assessmentthe category of premises is determined according to explosion and fire hazard. The category of premises and buildings is determined according to several criteria: — classes, quantity and degree of fire hazard of flammable substances and materials in the premises; — volumetric and planning properties of the premises; types of technological work carried out in them.
The fire hazard properties of substances and materials are determined based on the results of tests or calculations using standard methods, taking into account the parameters of pressure, temperature, and others. As a result of the fire risk assessmentThe following categories of premises are distinguished: A, B, B1-B4, G and D. Category A includes premises with an increased level of explosion and fire hazard, which contain: flammable gases, flammable liquids with a flash point of no more than 28 °C in such quantities that they can form explosive vapor-gas-air mixtures, the ignition of which develops a calculated excess explosion pressure in the room exceeding 5 kPa, as well as substances and materials capable of exploding and burning when interacting with water, atmospheric oxygen or with each other, in such quantities that the calculated excess explosion pressure in the room exceeds 5 kPa. Category of premises B — explosion and fire hazard: flammable dusts or fibres, flammable liquids with a flash point above 28 °C, flammable liquids in such quantities that they can form explosive dust-air or vapour-air mixtures, the ignition of which results in the development of a calculated excess explosion pressure in the premises exceeding 5 kPa. B1-B4 characterises the fire hazard of premises containing: flammable and hardly flammable liquids, solid flammable and hardly flammable substances and materials, substances and materials capable of only burning when interacting with water, atmospheric oxygen or with each other. Gradation by categories B1, B2, B3 or B4 is made depending on the quantity and method of placement of the fire load in the specified premises and its space-planning characteristics and on the fire hazardous properties of the substances and materials that make up the fire load. Category G – moderate fire hazard: non-flammable substances and materials in a hot, glowing or molten state, the processing of which is accompanied by the release of radiant heat, sparks and flames, and flammable gases, liquids and solids that are burned or utilized as fuel. Premises with reduced fire hazard are combined under category D: non-flammable substances and materials in a cold state.
Fire risk calculation method
Here we will provide a step-by-step plan demonstrating the fire risk calculation method. This methodology establishes the basic requirements for assessing the fire hazard in terms of fire risk in public buildings and structures, as well as public spaces. The methodology is set out in the Russian Federation State Standard. The calculation is based on the possible impact of fire hazards on people and the measures taken to reduce the frequency of their occurrence and consequences. According to the methodology, the fire safety risk for a person and the general social fire risk for people in the building are calculated. Individual and social fire risk is expressed in the probability of exposure Pb to hazardous fire factors, the list of which is presented in the «General Fire Safety Requirements». The principle of calculating the fire risk for each person — Qv in each building is carried out according to the formula: Qv = Qп Pпp (1 — РЕ) (1 — Pп.з), where Qp is the probability of a fire in a building per year, determined by calculation or on the basis of statistical data, Ppr is the probability of the presence of people in the building, during operation: 0.33 — in one shift; 0.67 — in two shifts; 1.00 — in three shifts; Re — probability of evacuation of people; Rp.z — probability of effective operation of technical fire protection solutions aimed at ensuring safe evacuation of people.Methodology for calculating fire risksincludes calculation of evacuation probability — Pe using the formula: Pe = 1 — (1 — Pe.p)(1 — Pd.v), where Pe.p is the evacuation probability along evacuation routes; Pd.v is the probability of leaving the building through emergency exits or with the help of other rescue means. The evacuation start time ?n.e for buildings (structures) without warning systems is calculated based on the results of a study of human behavior during fires in buildings of a specific purpose. If a fire warning system is available, ?n.e is taken equal to the response time of the system, taking into account its inertia. In some cases, it may be necessary to take measures to ensure additional conditions for the successful evacuation of people: — use of space-planning solutions and means that limit the spread of fire beyond the source; — arrangement of evacuation routes that meet the requirements for the safe evacuation of people during a fire; — installation of automatic fire detection systems (automatic fire alarm systems), notification and control of evacuation of people in case of fire; — application of collective protection systems (including smoke protection) from exposure to hazardous fire factors; — application of personal protective equipment for people from exposure to hazardous fire factors; — limiting the number of people in a building or structure to values that guarantee the safety of their evacuation from the building or structure in case of fire.