Equivalency - Revision history

Emma: Add 3 watermarked SVG illustrations from the Advanced visual plan

2026-11-02T16:12:20Z

Add 3 watermarked SVG illustrations from the Advanced visual plan

← Older revision		Revision as of 17:12, 2 November 2026
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	The IFEG calls for the same assumptions, models, calculations and input data in the trial and reference analyses. This requirement concerns a consistent analytical basis. The explicitly proposed design changes must still be represented, since their performance is the subject of the comparison. Unrelated changes to model assumptions would make the resulting difference harder to attribute.<ref name="I-21" />		The IFEG calls for the same assumptions, models, calculations and input data in the trial and reference analyses. This requirement concerns a consistent analytical basis. The explicitly proposed design changes must still be represented, since their performance is the subject of the comparison. Unrelated changes to model assumptions would make the resulting difference harder to attribute.<ref name="I-21" />
			[[File:fse-equivalency-v1.svg\|thumb\|upright=1.5\|alt=Reference and trial calculations share the analytical basis but contain their explicitly different design features.\|A comparison retains a common analytical basis while representing the proposed design differences. Based on Australian Building Codes Board et al. (2005), pp. 1.2-21–1.2-23.]]

	For example, if an evacuation comparison changes both a building feature and the assumed occupant characteristics, the reported improvement may arise from either change. The ABCB scenario framework identifies occupant characteristics separately from protection features for this reason. The report should distinguish fixed comparison assumptions from those deliberately changed to represent the alternative or a separate sensitivity case.<ref name="I-21" /><ref name="A-59" />		For example, if an evacuation comparison changes both a building feature and the assumed occupant characteristics, the reported improvement may arise from either change. The ABCB scenario framework identifies occupant characteristics separately from protection features for this reason. The report should distinguish fixed comparison assumptions from those deliberately changed to represent the alternative or a separate sensitivity case.<ref name="I-21" /><ref name="A-59" />
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	The IFEG evacuation example compares the margin between available safe evacuation time, ASET, and required safe evacuation time, RSET. For its comparative evaluation, the trial margin should equal or exceed the reference margin. The following calculation uses that principle with hypothetical times and a decision rule applied separately to each scenario.<ref name="I-22">Australian Building Codes Board et al. (2005), p. 1.2-22.</ref>		The IFEG evacuation example compares the margin between available safe evacuation time, ASET, and required safe evacuation time, RSET. For its comparative evaluation, the trial margin should equal or exceed the reference margin. The following calculation uses that principle with hypothetical times and a decision rule applied separately to each scenario.<ref name="I-22">Australian Building Codes Board et al. (2005), p. 1.2-22.</ref>
			[[File:fse-equivalency-v2.svg\|thumb\|upright=1.5\|alt=Bars compare the reference and trial margins in two scenarios, showing a pass in A and a failure in B.\|An improved margin in one scenario does not satisfy a separate failing comparison in another. Based on Australian Building Codes Board et al. (2005), p. 1.2-22, with hypothetical values.]]

	<div class="fse-equation">M = ASET − RSET;   M<sub>trial</sub> ≥ M<sub>reference</sub></div>		<div class="fse-equation">M = ASET − RSET;   M<sub>trial</sub> ≥ M<sub>reference</sub></div>
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	Operational conditions also matter after design. The Handbook connects the fire safety strategy with evacuation arrangements, management and ongoing reliability of protection systems. Where these conditions support the comparison, they need to be communicated through the building lifecycle. The demonstrated performance cannot be interpreted independently of the arrangements assumed to achieve it.<ref name="A-28" /><ref name="A-32" />		Operational conditions also matter after design. The Handbook connects the fire safety strategy with evacuation arrangements, management and ongoing reliability of protection systems. Where these conditions support the comparison, they need to be communicated through the building lifecycle. The demonstrated performance cannot be interpreted independently of the arrangements assumed to achieve it.<ref name="A-28" /><ref name="A-32" />
			[[File:fse-equivalency-v3.svg\|thumb\|upright=1.5\|alt=The equivalency conclusion is connected to evacuation, management and system reliability throughout building use.\|The conclusion remains tied to the operational arrangements and reliability assumed in the comparison. Based on Australian Building Codes Board (2020), pp. 28 and 32.]]

	The technical evidence should identify the basis on which relied-upon publications, standards and modelling methods support the claim. The ABCB Handbook includes this information in its description of supporting engineering reports. This enables a reviewer to distinguish a requirement taken from a reference document, a calculated result and an engineering assumption. Each plays a different role in the argument for the proposed solution.<ref name="A-4-6" /><ref name="I-23" />		The technical evidence should identify the basis on which relied-upon publications, standards and modelling methods support the claim. The ABCB Handbook includes this information in its description of supporting engineering reports. This enables a reviewer to distinguish a requirement taken from a reference document, a calculated result and an engineering assumption. Each plays a different role in the argument for the proposed solution.<ref name="A-4-6" /><ref name="I-23" />

Peter: New FSE wiki article: Equivalency (written by GPT-6)

2026-11-01T22:54:49Z

New FSE wiki article: Equivalency (written by GPT-6)

New page

'''Equivalency''' is the demonstration that an alternative fire safety solution achieves at least the safety performance of a defined reference solution. Van Rossum describes the principle as achieving the safety level associated with a prescribed provision through an alternative approach and its measures. The comparison concerns the safety outcome, rather than the physical identity of the measures.<ref name="V-1">Van Rossum (2027), Chapter 1, introductory discussion.</ref>

The International Fire Engineering Guidelines describe comparison at the level of an element, a subsystem or a complete fire safety system. The reference is the same building with the relevant features designed according to the identified prescriptive provisions. Consistent assumptions, models, calculations and inputs provide the basis for evaluating the proposed differences.<ref name="I-21">Australian Building Codes Board et al. (2005), p. 1.2-21.</ref>

Equivalency is therefore a defined assessment, with a specified reference, scope and decision rule. It does not establish that every possible outcome is identical or that fire risk has been eliminated. Its conclusion applies to the objectives, scenarios and conditions actually examined, supported by the agreed treatment of uncertainty and system performance.<ref name="I-21-26">Australian Building Codes Board et al. (2005), pp. 1.2-21–1.2-26.</ref><ref name="A-28">Australian Building Codes Board (2020), p. 28.</ref>

== The role of a reference solution ==

[[Building regulations|Building regulations]] often express fire safety requirements through specified features, dimensions or provisions. Van Rossum explains that these measurable limits do not necessarily identify a quantified acceptable probability of harm. Comparing an alternative with a compliant reference can establish a performance benchmark where the underlying goal has not been expressed as a numerical risk limit.<ref name="V-1-2">Van Rossum (2027), §1.2.</ref>

A reference derived from [[Prescriptive design|prescriptive design]] is consequently more than a label attached to a drawing. The assessment needs to identify the provisions represented and the resulting features relevant to the analysis. Otherwise, the supposed reference performance cannot be reproduced or related to the issue being assessed. The IFEG comparison explicitly refers to identified prescriptive provisions.<ref name="I-21" />

The ABCB Handbook explains this benchmark rationale within the framework developed for the 2019 National Construction Code. It also requires the validity of using that benchmark to be considered in each instance. This historical example supports a general analytical caution: the existence of a prescribed solution does not remove the need to examine its suitability as the chosen comparator.<ref name="A-15">Australian Building Codes Board (2020), p. 15.</ref>

A comparative assessment differs from an absolute assessment. The latter compares the trial design directly with objectives or performance requirements through agreed criteria, without a prescriptive reference design. Both approaches can form part of [[Performance-based design|performance-based design]], but their numerical questions differ. A report should identify which approach supports each part of its conclusion.<ref name="I-21" />

The source of the benchmark also matters when objectives extend beyond regulatory requirements. Van Rossum distinguishes public objectives from private interests such as property preservation and business continuity. A comparison directed at a regulatory objective does not automatically establish that a client's additional objectives are met. Those interests may need separate criteria and evidence.<ref name="V-1" /><ref name="V-1-2" />

== Defining the scope of the comparison ==

The assessment should start from the relevant departure or design question and identify the performance it could affect. The IFEG permits an element, subsystem or whole-system comparison, depending on the issue. That flexibility requires a clear boundary. An analysis of one component cannot automatically justify a conclusion about the complete building fire safety system.<ref name="I-21" />

Interactions can make that boundary wider than the immediately altered provision. The ABCB Handbook's account of the 2019 framework includes requirements from other sections or parts that are affected by a proposed solution. The engineering implication is to identify those connections before fixing the analysis scope. Evaluating only the provision being varied can omit a relevant effect elsewhere.<ref name="A-4-6">Australian Building Codes Board (2020), pp. 4–6.</ref>

The comparison also needs a defined set of fire scenarios. The ABCB Handbook describes selecting design fires, specifying active and passive protection status, identifying occupant characteristics and deriving comparative criteria. These are connected parts of the scenario description. A statement that the alternative is equivalent is difficult to interpret without knowing the conditions under which that statement was tested.<ref name="A-59">Australian Building Codes Board (2020), p. 59.</ref>

Hazard identification helps develop that set. The Handbook describes systematic consideration of different locations, fires, occupant characteristics and combinations of safety measures. Depending on the building, more than one location may require detailed evaluation within a prescribed scenario. A convenient model location is therefore not automatically the only location relevant to the comparison.<ref name="A-59" />

The chosen scenarios should also retain relevant differences between the reference and alternative. The Handbook notes that occurrence frequencies may require estimation when they vary between the two designs. A comparison of consequences alone would not capture such a change. The analyst needs to identify whether a design difference affects the outcome, its likelihood or both.<ref name="A-59" />

Scope should be agreed through the design brief, together with the methods, inputs and criteria. The IFEG process allows preliminary calculations to test the plausibility of a trial design before the full analysis. If the trial proves unacceptable, the brief can be revisited through the consultative process and another design developed.<ref name="I-2">Australian Building Codes Board et al. (2005), p. 1.2-2.</ref>

== Making the comparison consistent ==

The IFEG calls for the same assumptions, models, calculations and input data in the trial and reference analyses. This requirement concerns a consistent analytical basis. The explicitly proposed design changes must still be represented, since their performance is the subject of the comparison. Unrelated changes to model assumptions would make the resulting difference harder to attribute.<ref name="I-21" />

For example, if an evacuation comparison changes both a building feature and the assumed occupant characteristics, the reported improvement may arise from either change. The ABCB scenario framework identifies occupant characteristics separately from protection features for this reason. The report should distinguish fixed comparison assumptions from those deliberately changed to represent the alternative or a separate sensitivity case.<ref name="I-21" /><ref name="A-59" />

Consistent use of a method does not establish that the method is suitable. The IFEG asks for validation, fitness for the application and outputs that can be compared with the criteria. If a method cannot represent the effect of the proposed change, applying it twice does not demonstrate equivalence. The evidence must be capable of resolving the relevant performance question.<ref name="I-23">Australian Building Codes Board et al. (2005), p. 1.2-23.</ref>

A qualitative comparison may be appropriate for a limited issue where the agreed reasoning is sufficient. The IFEG requires the logic and supporting references to be documented. More complex issues generally require quantitative analysis, which can still be supported by qualitative arguments. The distinction concerns the evidence needed for the issue, rather than the length or appearance of the report.<ref name="I-21" />

Quantitative comparisons can be deterministic or probabilistic. A deterministic model predicts an outcome for stated conditions but does not provide the probability of that outcome. A probabilistic [[Fire risk assessment|fire risk assessment]] additionally needs information about events, frequencies or system reliability. Its conclusion depends on how scenarios and their consequences are combined.<ref name="I-22-23">Australian Building Codes Board et al. (2005), pp. 1.2-22–1.2-23.</ref>

The two approaches should not be confused in reporting. A trial that gives a longer evacuation margin in one deterministic scenario has improved that calculated result. It has not thereby demonstrated a specified percentage reduction in total fire risk. Such a claim would require the additional probabilistic structure and evidence appropriate to the risk measure being used.<ref name="I-22-23" />

For a risk comparison, the selected measure also needs to be stated. The ABCB Handbook distinguishes individual risk from societal risk and calls for both to be considered in its comparative strategy. A change that affects the number of people exposed may therefore require attention beyond the risk at one location. Matching a single aggregate number does not explain every relevant distribution of harm.<ref name="A-22">Australian Building Codes Board (2020), p. 22.</ref>

== Criteria and a worked comparison ==

[[Acceptance criteria|Acceptance criteria]] state how the comparison will be judged. The IFEG requires the same criteria for the reference and trial, with trial performance no worse than reference performance. The direction of improvement depends on the quantity: more time available for evacuation and less harmful exposure are different forms of favourable outcome.<ref name="I-25-26">Australian Building Codes Board et al. (2005), pp. 1.2-25–1.2-26.</ref>

The IFEG evacuation example compares the margin between available safe evacuation time, ASET, and required safe evacuation time, RSET. For its comparative evaluation, the trial margin should equal or exceed the reference margin. The following calculation uses that principle with hypothetical times and a decision rule applied separately to each scenario.<ref name="I-22">Australian Building Codes Board et al. (2005), p. 1.2-22.</ref>

<div class="fse-equation">M = ASET − RSET;   M<sub>trial</sub> ≥ M<sub>reference</sub></div>

{| class="wikitable"
! Quantity !! Meaning !! Unit
|-
| ASET || Available safe evacuation time for the selected scenario and tenability criteria || s
|-
| RSET || Required safe evacuation time for the assumed occupants and evacuation strategy || s
|-
| M || Additive evacuation time margin || s
|}

{| class="wikitable"
! Hypothetical scenario !! Design !! ASET (s) !! RSET (s) !! Margin (s)
|-
| A || Reference || 480 || 360 || 120
|-
| A || Trial || 510 || 360 || 150
|-
| B || Reference || 390 || 360 || 30
|-
| B || Trial || 380 || 360 || 20
|}

In scenario A, the trial increases the margin by 30 s and satisfies the chosen comparative criterion. In scenario B, it reduces the margin by 10 s and fails that criterion. Both trial cases still have ASET greater than RSET. That observation alone would miss the poorer performance relative to the reference in scenario B.<ref name="I-22" />

The example therefore does not support equivalency across the stated scenario set. The improvement in A cannot simply be used to cancel the shortfall in B under the adopted per-scenario rule. No occurrence frequencies have been assigned, so the table also provides no basis for calculating or comparing expected risk. It illustrates a decision rule, not a validated building analysis.<ref name="I-22-23" /><ref name="I-25-26" />

Several criteria may be used together where the objectives require them. The IFEG lists evacuation, exposure, structural and other outcome parameters, depending on the objective. A satisfactory time comparison therefore answers only its defined question. It does not automatically demonstrate equivalent protection of adjacent property or satisfy another separately agreed performance criterion.<ref name="I-25-26" />

The reference result has its own scope of meaning. It is the performance calculated for the selected compliant arrangement under the stated conditions, rather than an independently established universal level of safety. The Handbook's requirement to consider benchmark validity is relevant here. A defensible conclusion explains why the reference represents the issue being assessed and why the selected comparison is informative.<ref name="A-15" /><ref name="I-21" />

== Uncertainty, reliability and sensitivity ==

A comparative result remains conditional on its inputs and methods. The IFEG distinguishes sensitivity studies, uncertainty studies and examinations of redundancy. Sensitivity studies vary inputs to investigate their influence; uncertainty studies examine uncertain information; redundancy studies consider alternative means of achieving a safety function. These approaches help reveal limitations that a single nominal comparison can conceal.<ref name="I-24">Australian Building Codes Board et al. (2005), p. 1.2-24.</ref>

Relevant sensitivity changes can include fire growth, partial smoke extraction failure, slower movement or exit availability. The IFEG identifies these as examples to be considered in the brief. The selected cases should relate to the mechanism supporting the proposed equivalency. The applicable criteria and extent of the studies need agreement alongside the principal analysis.<ref name="I-24" />

System reliability becomes particularly important where the comparison depends on a protection measure operating as intended. The ABCB Handbook requires both the status and impact of active and passive features to be defined for reference scenarios. Its life safety strategy also connects the assumed performance with management arrangements and maintaining system reliability throughout building use.<ref name="A-59" /><ref name="A-28" />

The IFEG notes that explicit safety factors may be unnecessary in a comparative evaluation using the same methods and assumptions for both designs. This does not establish that every uncertainty disappears. The same guidance requires consideration of uncertainty, reliability, redundancy and consequences. A comparison should expose its uncertainty treatment rather than merely describe both calculations as equally conservative.<ref name="I-24" /><ref name="I-26">Australian Building Codes Board et al. (2005), p. 1.2-26.</ref>

Sensitivity cases can have different criteria or factors where this has been agreed and justified. The IFEG discusses this possibility to avoid excessive conservatism. The report must distinguish such cases from the principal comparison. Changing the criterion only after an unfavourable calculation would obscure the basis on which equivalency was originally being assessed.<ref name="I-26" />

== Documentation and continuing conditions ==

The conclusion should identify the reference, alternative, objectives, scenarios, methods and criteria that support it. The ABCB design brief process records the proposed strategy and the inputs to the analysis so stakeholders understand the expected performance. These records make the equivalency claim assessable and preserve the conditions on which it depends.<ref name="A-32">Australian Building Codes Board (2020), p. 32.</ref>

Agreement is sought during that process, but unresolved views should remain visible. The ABCB Handbook calls for dissenting views to be recorded and carried forward for consideration by the appropriate authority. Technical disagreement is therefore part of the assessment record. Removing it would make the final conclusion appear more settled than the documented process supports.<ref name="A-32" />

Operational conditions also matter after design. The Handbook connects the fire safety strategy with evacuation arrangements, management and ongoing reliability of protection systems. Where these conditions support the comparison, they need to be communicated through the building lifecycle. The demonstrated performance cannot be interpreted independently of the arrangements assumed to achieve it.<ref name="A-28" /><ref name="A-32" />

The technical evidence should identify the basis on which relied-upon publications, standards and modelling methods support the claim. The ABCB Handbook includes this information in its description of supporting engineering reports. This enables a reviewer to distinguish a requirement taken from a reference document, a calculated result and an engineering assumption. Each plays a different role in the argument for the proposed solution.<ref name="A-4-6" /><ref name="I-23" />

== Notes ==
<references />

== References ==
* Australian Building Codes Board. (2020). ''Fire safety verification method handbook'' (Version 1.1).
* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing. (2005). ''International fire engineering guidelines''.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Fire Safety Design & Regulation]]