Ignition Techniques

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There are different ignition techniques that can be used to complete a controlled burn. When and where fires are started in relation to the area to be burned and the direction of the wind, can determine how hot the fire becomes and how fast the fires moves. Ignition techniques allow the person conducting the fire to control the fire to some extent. The two ignition techniques most commonly used are: 1) the back fire, 2)  the flank fire.

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To see a video illustrating a Back Fire and Flank Fire, click here.

 

Back Fire – This ignition technique is the easiest and safest method for completing a prescribed burn, provided wind speed and wind direction remain steady. It is generally used by novices of prescribed burning because the rate of spread is relatively slow compared to other firing techniques and more easily controlled. The back fire is also the most common ignition technique used, and should always be the first line of fire set in any prescribed burning sequence. A back fire is always started along a firebreak or other barrier at the most leeward (downwind) edge of the burn area and allowed to slowly burn back into the wind. This method can be used successfully provided that a wind is consistently blowing in one direction, relative humidity is low, and there is a continuous source of fine dead fuels throughout the area to carry the burn.

Because a back fire burns slowly against the wind, completing the prescribed burn using only a back fire may take several hours.

When used with any ignition technique, the back fire is ALWAYS set first and allowed to burn an area at least 10 m into the block, prior to setting any other fires.

This helps ensure that any fire moving in a windward direction as a result of additional fires ignited upwind will be contained within the blackened area created behind the back fire.

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Flank Fire – The flank fire technique employs the use of fire set in lines parallel (flanking) to the wind. Although flank fires can be ignited within the central portions of the burn area, extensive knowledge of fire behavior and experience is required, and therefore, it is not recommended for use by most landowners.

 

For the purpose of this resource, discussion is limited to the use of flank fires along the outer flanks of the area to be burned, along established firebreaks. Flank fires are typically used along the flanking control lines (firebreaks) to burn vegetation within the burn area away from the control lines, similar to the results obtained by a backing fire.

 

Flank fires should not be ignited until a back fire has burned and blackened a strip wide enough along the baseline to control and contain any upwind fire resulting from the ignition of flanking fires.

The use of flank fires reduces the amount of time necessary to complete a prescribed burn. To properly employ the flank fire technique, at least two persons carrying their own ignition source, are needed to simultaneously set the flanking fires.

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