Control measure Understand signs and symptoms of flashover
Control measure knowledge
The previous section provides a scientific description of events that firefighters may encounter but most importantly firefighters should be able recognise and understand the following signs.
Signs of room flashover include:
- High heat conditions or flaming combustion overhead
- The existence of ghosting tongues of flame
- A lack of water droplets falling back to the floor following a short burst fog pattern being directed at the ceiling
- A sudden lowering of the smoke layer (previously referred to as the neutral plane)
- The sound of breaking glass as windows or glazing begin to fail from exposure to heat, possibly causing a visible rise in the smoke layer (previously referred to as the neutral plane)
- A change in smoke issuing from a window (seen from the exterior), with increasing velocity, as if issuing under pressure, and a darkening of smoke colour towards black
- The sudden appearance of light-coloured smoke (pyrolysis) from low-level items being subjected to high heat flux from the hot gas layer
This video demonstrates the phenomenon of flashover.
Where it is necessary to use a combination of direct and indirect firefighting techniques and gas cooling, firefighters should take care at all times to ensure that direct firefighting jets/sprays do not impact negatively on the conditions or on firefighting teams as they move through a structure when deployed for internal firefighting operations.
Summary of key fire behaviour indicators
Fire behaviour indicator | Hazard information | |
1 | Slow-moving light-coloured smoke issuing from an opening | Early-stage fire development or smoke issuing some distance from the fire compartment |
2 | Fast-moving darkening smoke issuing from an opening | Impending flashover |
3 | Heavily darkened or heat-crazed windows | Under-ventilated fire conditions threatening backdraught or smoke explosion |
4 | Pulsing (in and out) darkened smoke movements around closed doors and windows | Fire development heading towards backdraught |
5 | Very hot doors or windows (feel with back of the hand) | Under-ventilated fire conditions threatening backdraught, smoke explosion or thermal runaway (flashover) |
6 | Sudden reversal of smoke issuing from an opening, causing smoke to head back into the compartment/building | The fire is rapidly developing and in need of more oxygen (impending flashover or backdraught), or a gusting wind-driven fire event is occurring |
7 | A rapid lowering of the smoke layer (previously referred to as the neutral plane) | Impending flashover |
8 | A rising of the smoke layer (previously referred to as the neutral plane) | A vent opening may have occurred at another location in the compartment/building |
9 | Turbulence or rising and falling (bouncing) in the smoke layer (previously referred to as the neutral plane) | Rapid fire development may be occurring |
10 | Heat radiating down from the smoke layer (previously referred to as the neutral plane) | Impending flashover |
11 | Detached 'ghosting' tongues of flame moving around the fire compartment | Impending flashover |
12 | Flaming combustion seen near the ceiling or at the smoke interface | Impending flashover |
13 | Smoke seen issuing from closed windows, doors or roof eaves, as if under pressure | Under-ventilated fire and impending backdraught |
Strategic actions
Fire and rescue services should:
- Provide information, instruction and training to ensure all personnel are aware of the indications, safety measures and actions to take for potential flashover events
- Develop tactical guidance and support arrangements to ensure the safety of personnel when dealing with potential flashover events
- Maintain systems and processes to acquire and act on operational information on the occurrence of flashover events at operational incidents
- Share operational information and organisational learning on flashover events with relevant stakeholders
Tactical actions
Incident commanders should:
Where flashover conditions are suspected, consider direct firefighting techniques
- Consider employing a combination of direct firefighting and gas cooling to control conditions
Brief crews to carry out self-protection, door entry and compartment firefighting techniques
TRAINING SPECIFICATION
Knowledge and understanding
| Control measure element | Learning outcome |
|---|---|
Identify and react to signs and symptoms of flashover |
Understand the following:
|
Practical application
| Control measure element | Learning outcome |
|---|---|
Understand signs and symptoms of flashover |
Demonstrate the ability to:
|