Initial Key parameter Egress Assessment

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Welcome to the Initial Key parameter Egress Assessment tool

This tool is designed to estimate evacuation conditions for shared evacuation situations, for example shopping malls and multi‑storey buildings. The key figure assessment is based on the number of occupants, available egress width, and ceiling height. In general, the more people or floors depend on the same exit, the more critical the evacuation conditions become. To get started:

Add floors – Use the menu bar to set the number of floors in your building.

Add exits – For each floor, add all available exits. Choose between Door directly to outside, Internal stair and Emergency stair

View results – When all exits are defined, click Result to evaluate evacuation conditions for each floor.

Contact Fire Engineer – If results show that detailed evaluation should be undertaken, contact a Fire Expert for assistance. Fire Engineers at Bengt Dahlgren, creaters of this tool, is available for further assistance if needed.

Floor	Effective width	MOC design objective	State of conditions	Actions required

This appendix describes the methods used to assess evacuation widths, providing an understanding of the tool and how to input values correctly.

Required material

Floor plans detailed enough to identify:
- Staircase widths (narrowest point)
- Evacuation flow directions and connected floors
- Routes leading directly outside
Gross and/or customer area for IKEA
Ceiling height (concrete to concrete)

Early-stage assumptions:

Stair and door widths do not reduce staircase capacity
Stair pinch points do not restrict flow
Evacuation routes to the outside are unobstructed
Evacuation route widths are assumed constant on all floors

Input Steps

Define number of floors: Determines how flows are merged. Tool is valid for IKEA areas up to 3 floors above discharge level; basements can be assessed inversely.
Identify areas (m²):
- If customer area is known: 1 person per 4 m².
- If not: gross area × 0.7, then 1 person per 4 m².
- If maximum occupant capacity (MOC) is known, it can be entered directly.
Define exits and openings: Mark stairs, exits, and openings on plans. Assign each a unique name/number and width.
Define accessibility and discharge: Identify type of exit (emergency stair, internal stair, or exit door). Mark whether it leads to outside or common area, and if shared with other tenants.
Define calculation boundary: Openings to common areas should be regarded as exits only when the calculation boundary is defined at the storefront. Where common areas are included within the calculation boundary, only final exits to the exterior should be considered.

Tool Function

The tool compares evacuation widths per floor against the maximum occupant capacity (MOC) and accounts for shared and merging flows. Results are categorized by preset width per person levels.

Calculation assumptions:

Merging flows: Staircases follow the “zipper principle” where effective width decreases per added floor:
- Floor 1: 50%
- Floor 2: 25%
- Floor 3: 12.5%
- Floor 4–5: 6.25%
Shared routes: If IKEA shares an emergancy stair with another tenant, the effective width is reduced by 50%.
Internal stairs: Internal egress from served floors but do not increase evacuation width to the outside. Internal stair width exceeding 50 % of the total floor width is ignored.
Common area: Common areas are considered semi-safe. As such, common area width exceeding 50 % of the total floor width is ignored.
Performance benchmarks: The method uses thresholds (e.g. 1 m width per 150–350 people) as experience-based indicators, similar to simulation outcomes. High ceiling heights are known to reduce width demand.