The assessment of the risk of fire is part of the overall approach to the assessment of occupational risks.
It consists of :
- eliminate the causes of a fire (actions in particular on combustible products and sources of ignition) by implementing both technical and organizational measures,
- limit the importance of the human and material consequences , in particular by an effective detection allowing to intervene in time to evacuate people and to intervene with the internal means (extinguisher, cocked fire cock - RIA) on the beginning of fire.
- promote the evacuation of people and the intervention of emergency services.
Fire Risk Assessment Approach |
As the elimination of all fuels and / or ignition sources is difficult to implement, it is essential to put in place measures to react quickly and effectively to the start of a fire and to limit its effects. . These measures aim to:
- facilitate the evacuation of those present or bring people with disabilities who require it to safety,
- limit the spread of the fire,
- promote the intervention of the emergency services.
For this, three axes are to be privileged:
- the design and layout of workplaces and situations,
- the risk assessment process,
- technical, organizational and employee information / training assessment measures.
In order to put in place the fire risk assessment approach and to make it sustainable, it is essential to obtain the involvement of all company personnel, from general management to the operator . It is also advisable to:
- define and list internal skills,
- designate the "fire" manager. This must be surrounded by internal skills (maintenance manager, occupational physician, etc.) and external (insurers, departmental fire and rescue service, etc.),
- involve employee representative bodies (CSE, etc.),
- plan the different stages of the chosen approach,
- communicate and inform all staff on actions undertaken and carried out.
Assessment of fire risk / Location and design of premises
The most effective preventive measures are those applied upstream, from the design and construction of the premises . They make it possible to guarantee good evacuation conditions, to take better account of isolation, separation and safety distances to prevent or limit the spread of the fire. Assessment must also apply when choosing materials in order to ensure the stability of the structure and reduce the emission of gases and fumes in the event of a disaster. In addition, it is necessary to take into account the foreseeable evolution of the company.
When designing the premises, it is therefore necessary:
- split the buildings into separate units with separate fire-resistant structures (compartmentalisation),
- isolate the premises at risk from other premises ,
- choose materials according to their fire behavior
- design clearances (exits, doors, corridors, stairs, etc.) whose number and size are sufficient to facilitate evacuation and emergency access,
- set up effective smoke extraction to guarantee smoke-free clearances, to evacuate them to privileged places, thus limiting the spread of the fire and facilitating the evacuation of people and the intervention of emergency services.
Examples of fire risk areas that can be isolated from other rooms
- Storage of finished products
- Storage of chemicals
- Storage of gas cylinders and tanks
- Boiler room
- Waste dumpsters
- Battery charging room
© GJ Plisson for INRS
Behavior in fire risk assessment
The fire behavior of an element in the event of fire is assessed according to its fire resistance but also by the reaction to fire of its constituent materials:
- The reaction to fire of a material is characterized, among other things, by its ability to be combustible and its ease of ignition. 7 criteria (A1, A2, B, C, D, E and F) thus define the European classification (Euroclasses) for construction materials. Indices like "fl" (for "floor") can be added specifically for certain materials (for example, those dedicated to floors).
- Fire resistance corresponds to the time during which the building elements can play the role assigned to them. 3 criteria (Eurocodes) are used in particular to determine it: load-bearing capacity or resistance (R), flame tightness and absence of gas emission (E) and thermal insulation
For each of these criteria, the classification is always associated with a duration (in minutes for Eurocodes, for example "REI 120"; in fraction of hours for the others, for example "firewall 2h").
The materials used for the structures must allow them to remain stable at least during the evacuation of people.
Clearances
A clearance corresponds to all the parts of a construction which allow the evacuation of occupants (door, exit, exit, corridor, horizontal circulation, circulation zone, staircase, ramp, etc.).
Combined with sound and visual alarms carefully installed, the clearances must allow people to be evacuated quickly and in complete safety. They are also used to reach the secure waiting areas .
They are always accessible, free and clearly indicated. Their number, size and location comply with the values set by the regulations (see the legal aid Fire assessment in the workplace - TJ 20 )
Smoke extraction
Smoke extraction allows the evacuation of fumes and hot gases, which facilitates the evacuation of personnel, the intervention of emergency services and limits the risk of the fire spreading.
Smoke extraction devices must be included in the design of an establishment.
These are generally openings in the roofs or in the upper part of the walls in order to evacuate the fumes and hot gases. Their opening can be triggered manually or automatically. Fresh air is brought in through openings in the lower part. Their surface must be in relation to the surface of the room considered.
Fire safety system (SSI)
The fire safety system (SSI) must also be designed from the design of a business or building. It is made up of all the elements used to collect information or all orders related to fire safety alone, to process them and perform the functions necessary to secure a building or an establishment in the event of fire. The SSI consists, for the most complex, of a fire detection system (SDI) and a fire safety system (SMSI).
For more information, see the Fire and Workplace brochure. Assessment and organization in the company
Fire detection system (SDI)
The purpose of this system is to detect and signal the start of a fire at any time. The main objective is to obtain an early and sure detection of the beginning of a fire. The SDI includes in particular automatic detectors and manual call points.
When installing it, care must be taken to choose detectors suited to the types of fires likely to be triggered (predominance of smoke, flames, combustion gases, etc.) and to the activity of the room (pollution present, temperature, ventilation…).
The choice of the location of the detectors depends on:
- the height of the room ,
- the location and configuration of the ceiling ,
- the direction of air currents,
- the location of the air inlets and ventilation ducts,
- accessibility during maintenance operations (cleaning and testing).
Main types of detectors as Fire Risk Assessment
- Optical type smoke detectors: detection of combustion aerosols
- Thermostatic or thermovelocimetric heat detectors: detection of an abnormally high temperature or temperature rise
- Flame detectors: detection in the infrared or ultraviolet range
- Special detectors combining several technologies.
Fire safety system (SMSI)
This system includes all the equipment that performs the functions necessary for securing a building or establishment in the event of a fire: compartmentalization, evacuation of people, management of clearances, smoke extraction, etc.
It includes a signaling and manual control unit associated with actuated safety devices (fire doors and dampers, smoke extraction systems, etc.).
Installation of extinguishing equipment
Fire-fighting equipment as well as fixed extinguishing installations must be carefully chosen so that they are suitable for the types of fires likely to break out and be present in sufficient numbers. They must be checked regularly so that they are operational at all times.
Fire risk assessment: identify risky situations
The fire risk assessment involves identifying situations where the three elements of the fire triangle are combined (fuel, oxidizer and ignition source).
The “memory” of the company or the branch of activity (fire experience feedback, experience of dangerous situations) can also help identify risky operations or situations.
The origins of a fire are first of all due to the presence of combustible products . It's a priority :
- establish the list of products present,
- to determine their physical state (liquid, gas, solid, powder, aerosol, etc.),
- to know their physicochemical characteristics (for example, the flash point of a liquid: the lower it is, the more easily flammable the product),
- to identify their conditions of use and storage (quantities, temperature, room or dedicated “EI” cabinet (fire break for a determined time), presence of retention tanks, etc.).
The origins of the fire can also be linked to the processes implemented (temperature and pressure conditions, exothermic reactions, decomposition products, cooling conditions, etc.), or even to their potential malfunctions (cooling system shutdowns, gas leaks. products, foreseeable breakdowns, accidental product supply stoppages, etc.).
The sources of ignition to be identified are of various origins:
- thermal : hot surfaces, heaters, open flames, work in hot spots….
A cigarette lit like an open flame is an active source of ignition. For example, the end of a lit cigarette reaches 1000 ° C during aspiration. Hot spot work (torch welding, flame cutting, etc.) are major sources of claims: they are responsible for around one in three fires;
- electric : sparks, heating….
The obsolescence, improvised nature or overload of certain installations lead to overheating which is the cause of a good number of fires (about one in three fires);
- electrostatic : spark discharges ...
Static electricity can be the source of sufficiently energetic sparks to be a source of ignition;
- mechanical : sparks, heating ...
Heating and sparks of mechanical origin, resulting from friction, shock and abrasion, or failures (bearings, bearings, etc.) can be the cause of very high temperatures and / or projections of incandescent particles;
- climatic : lightning, sun ...
A lightning strike can constitute a direct or remote source of ignition by inducing overvoltages or heating in the equipment;
- chemical : exothermic reactions, self-heating, reaction runaway ...
Chemical reactions can give off enough heat to be a source of ignition;
- bacteriological : self-heating
Bacterial fermentation can cause the release of heat and promote the conditions for initiating self-heating.
It should also be noted that an explosion can be the source of ignition of a fire just as a fire can be the source of ignition of an explosive atmosphere.
The results of the assessment must be reflected in the single document . Beyond strict compliance with the regulatory obligation, this document must enable the employer to draw up an action plan defining the assessment and protection measures appropriate to the fire risk .
The action plan, in particular with regard to the fire risk, will be based on criteria specific to the company (probability of occurrence, feared seriousness, frequency of staff exposure, number of people potentially concerned, etc.). It will make it possible to define priorities and help in the planning of actions to prevent and protect against fire.
Preventative measures to avoid fire risk
At the end of the assessment, the employer puts in place a certain number of preventive measures intended to reduce or even eliminate the risk of fire or the consequences thereof. A coordinated approach with the insurer allows the implementation of a monitoring plan / business continuity plan.
Avoid the risk
To avoid the risk of fire, it is necessary to act, at a minimum, on one of the vertices of the fire triangle:
- fuels,
- oxidizers,
- sources of ignition.
Assessment Actions on fuels
- Replace the combustible product with one that is non-combustible or less combustible
- Intervene on the state of division of matter (the more the state is divided, the easier and faster the combustion)
- Limit the quantities used and stored
- Capture fuel emissions
- Clean frequently by vacuuming and tidy the premises
Assessment Actions on oxidizers
- Reduce the oxygen content, in order to make the atmosphere non-flammable, by introducing an inert gas (nitrogen, argon, helium, etc.). However, be aware of the risk of hypoxia (reduction in the supply of oxygen to the various tissues of the body) in the event of an employee entering the affected area.
- Isolate oxidizing products (oxygen, peroxides, etc.) from combustible products
Assessment Actions on ignition sources
Actions on processes or materials
- Cooling (chemical reaction, heating due to gas compression, etc.)
- Earthing, equipotential bonding
- Electrical equipment and installations compliant with installation standards (for low voltage, NF C 15-100)
- Suitability of electrical and non-electrical devices for the area at risk of explosion
- Decrease in the surface temperature of the heating elements
Implementation of maintenance and regular checks
- Electrical installation
- Detectors of temperature rise, pressure, or degradation products (carbon monoxide detectors)
- Explosimeters to verify that the concentration of gaseous fuels is maintained outside their range of flammability
- Infrared thermography to detect hot spots at insta