Sub Systems as defined by the International Fire Engineering Guidelines. (IFEG)


When considering fire safety within a building there are a set of 6 Sub Systems that assist in analyzing the best fire safety system. These six Sub Systems are represented as SSA to SSF and they in some shape interact with each other.


SSA.  Fire Initiation and Development and Control.

SSB.  Smoke Development and Control.

SSC.  Fire Spread and Impact and Control.

SSD.  Fire Detection, Warning and Suppression.

SSE.  Occupant Evacuation and Control.

SSF.   Fire Service Intervention.



The relationship between each sub System is explained below.



SSA has a relationship with SSB and SSC as lots of smoke and heat are produced, during a fire.


SSB deals with Smoke Management which has an impact on the development of a fire with flashover and back draft.


SSC also interacts with SSB because this could have an impact with the amount of smoke and temperatures that are produced so leading to flashover and back draft.


SSD also has an impact on SSA because this will determine the fire spread to any adjoining compartments or buildings. SSD provides a warning of a fire and engages any suppression systems fitted. This can also have a major impact on SSB by initating any smoke management systems. SSD also interacts with SSC controlling any spread of a fire with any of the suppression systems that are in place.


SSE has a marriage with SSD which also has very strong links to SSA SSB, SSC and SSD control the tenable conditions of the building providing time for Available Safe egress  Time (ASET) and Required Safe Egress Time)  (RSET).


If the Subsystems did not interact this would affect and possibly delay SSF. All of the Sub Systems need to be effective so that SSF comes into play. SSA linking to SSD has a crucial role in notifying the Fire service and warning the occupants of the building SSB and SSC are also critical Sub systems linked to SSF as Smoke development and spread would have a major impact on control and extinguishment.


To summarize the International Fire Engineering Guidelines says there are interactions between all six Sub systems evidenced by the inputs and outputs of each sub System. Many different analysis metrologies could be used for each sub system. If for example using a Probilistic or Quantitative approach in SSA this would have a huge impact on all other Sub Systems in terms of Heat Release rates, Smoke yields fire Spread, ASET , RSET times and Fire service intervention.



This photo shows a simple door wedged open.  This door is in fact a fire door with an FRL 0f  -/120/60.  You will also notice that there is an electronic holding open device fitted to the door which was perfectly serviceable.  However because the crates are in the way, this is preventing the door from opening fully affecting evacuation.  The crates in the fire rated corridor are reducing the egress width to less than a metre.  more importantly the fire resistance has been breached.

Below I have explained in very broad terms, how many sub systems are affected by a simple wooden wedge and discarded crates.  These items have very little monetary value but do have very serious life safety issues.



SSA.   Fire Initiation and Development and control?    Yes the door being wedged open has breached the fire compartmentation not containing the fire in the fire rated compartment.

SSB.  Smoke development and spread and control?   Yes again the door remaining open has a serious impact on smoke spread into the adjoining compartments.

SSC.  Fire Spread and Impact and Control?  Yes the fire could spread beyond the compartment that it started in due to barrier failure.

 SSD.  Fire Detection Warning and Suspression.  Yes the susspression system could activate, however with the door being open the  smoke would spread to the ajoinging compartment

SSE.  Occupant Evacuation and Control?   Yes occupant evacuation is severely jeopardized as the door cannot be fully opened.  Having an effect on ASET.  Further to this occupant evacuation would be severly jepordized with the smoke entering the compartment.

SSF.  Fire Services Intervention?   Yes this impacts the search, rescue, attack, control and extinguishment of the fire.