Question 1

What is the SLAB model and why is it important?

Accepted Answer

SLAB (Simulating Large Atmospheric Bodies) is a dense gas dispersion model developed by Lawrence Livermore National Laboratory (Ermak, 1990) and listed among the alternative models of the EPA Guideline on Air Quality Models. Unlike Gaussian models, it accounts for the slumping and entrainment of gases heavier than air, such as LPG, chlorine or ammonia. TekRisk implements SLAB in the browser and draws its results on the map.

Question 2

What's the difference between SLAB and Gaussian dispersion?

Accepted Answer

Gaussian models treat the gas as passive: it moves and spreads with the air. SLAB accounts for dense gas behavior: gases heavier than air slump, spread sideways and travel along the ground, mixing with air more slowly. For releases of heavy gases this changes the shape and reach of the cloud.

Question 3

What source types does TekRisk's SLAB support?

Accepted Answer

TekRisk supports all 4 SLAB source types: (1) Evaporating pool - continuous ground-level release, (2) Horizontal jet - pressurized release, (3) Vertical jet - elevated stack release with plume rise, (4) Instantaneous/puff - short-duration release.

Question 4

How accurate is TekRisk's SLAB implementation?

Accepted Answer

TekRisk implements SLAB as documented by Lawrence Livermore National Laboratory. For a pool evaporation case (GASPRB), its concentrations match the original Fortran program within −0.8 % to +0.2 % and the distances to 100 / 50 / 25 % of the LFL within 2 %. The jet and instantaneous sources have not been benchmarked yet; see the model validation page (tekrisk.com/en/docs/validation).

Feature	TekRisk	SLAB Model	Advantage
Cloud-Based	Included	Not included	TekRisk Advantage
GUI Interface	Included	Not included	TekRisk Advantage
No Command Line	Included	Not included	TekRisk Advantage
Dense Gas Dispersion	Included	Included	Equal
4 Source Types	Included	Included	Equal
Interactive Maps	Included	Not included	TekRisk Advantage
Visual Results	Included	Not included	TekRisk Advantage
Combined Fire/Dispersion	Included	Not included	TekRisk Advantage
QRA Integration	Included	Not included	TekRisk Advantage
Pricing	Free · Pro US$59.99/mo	Free (command line)	Equal
Free Tier Available	Included	Included	Equal
Documentation	Included	Included	Equal

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