What AURA is used for
AURA estimates how far the effects of an accidental release of a flammable or toxic material can reach. It is a screening tool: quick, transparent calculations that show which scenarios matter and how large their hazard zones are.
You describe a leak. AURA works out the release rate, the cloud or pool it forms, and the distances to fire, explosion and toxic effects, then puts them in one report.
From a leak to a hazard distance
Purposes it serves
Following up HAZID and HAZOP actions
"How far could this leak reach, and does it get to the control room?"
Put a number on a hazard raised in a study, so the action can be closed, kept or escalated.
Source term · Dispersion · Summary
Layout and separation distances
"Is this tank far enough from its neighbour, the fence and the muster point?"
Distances to 37.5, 12.5, 6.3, 4.7 and 1.6 kW/m² for each fire, and to 70 down to 2 kPa for an explosion.
Jet fire · Pool fire · Tank fire · Explosion
Emergency response planning
"Which area do we evacuate for a chlorine leak at night with light wind?"
Distances to IDLH, ERPG and AEGL limits and to 1, 10 and 50 % fatality, for the weather cases you plan against.
Weather · Dispersion · Toxic effects
Shelter in place or evacuate
"Are people safer indoors while the cloud passes?"
Indoor and outdoor concentration against time and the fatality estimate for each, for a building's air-change rate.
Toxic effects
Fire protection basis for tank farms
"How much cooling water does the next tank need, and for how long will this one burn?"
Radiation on a neighbouring tank, cooling water flow, level regression, burn-out time and time to boilover.
Tank fire · Pool fire
Escalation and knock-on events
"Can this jet fire cause the LPG bullet beside it to fail?"
Link the fire to the vessel it threatens. The radiation on the vessel is compared with the escalation limit and the BLEVE is assessed.
Scenario links · BLEVE and fireball
Basis for gas and fire detection
"How big is the flammable cloud from a 10 mm leak, and how wide?"
Reach and width of the cloud at the LFL and at a part of it, the flammable mass, and the outline drawn in plan.
Dispersion · Flash fire · Summary
Screening before detailed modelling
"Which of these forty scenarios deserve a detailed integral or CFD study?"
Run all of them quickly, rank them by hazard distance in the project report, and send only the governing ones for detailed work.
Projects · Project report · CSV
Management of change and what-if studies
"What changes if we raise the operating pressure or enlarge the bund?"
Copy a scenario or open a new revision, change one input and compare. Earlier revisions stay on record.
Scenarios · Revisions
Supporting safety documentation
"Where did this distance in the safety report come from?"
Each report lists the inputs, the model, its notes, the material data with sources, and who calculated and issued it.
Reports · Audit log
Reviewing an incident or near miss
"What could that release have done on a worse day?"
Rebuild the release from what is known and look at the outcomes it did not have, under other weather or ignition.
Source term · all outcome pages
Training and awareness
"Why does stability class F give such long toxic distances?"
Every page shows its equations and states its assumptions, so the effect of wind, hole size or inventory can be shown live.
Method panels · Verification
What it can model
| Event | Method | What you get |
|---|---|---|
| Gas or liquid release | Orifice flow, choked or sub-sonic, gas discharge coefficient by Bragg's method; flash and rain-out; choice of equation of state | Release rate, airborne and liquid parts, duration |
| Pressure vessel | Gas blowdown through a hole, adiabatic or isothermal; liquid drainage under pressure | Inventory, rate, pressure and mass against time |
| Pipe | Flow with friction to a break (Fanno for gas); Wilson model for a long gas pipeline; pumped liquid line | Release rate, mass and duration |
| Draining tank | Level integration for vertical, horizontal and spherical vessels | Level, rate and mass against time |
| Liquid pool | Spreading to the minimum depth of the ground or a bund; evaporating or boiling, with heat from the ground, the air and the sun | Pool size and evaporation rate |
| Vapour cloud | Gaussian plume (McMullen / Hosker coefficients with the surface roughness, or Briggs) and puff; Britter-McQuaid for dense gas | Concentration, distances to LFL and UFL, flammable mass |
| Toxic exposure | Toxic load and probit; indoor concentration | Distances to IDLH, ERPG, AEGL and fatality levels |
| Jet fire | Chamberlain conical flame (Cook for two-phase jets), Johnson for horizontal gas jets, or point source with API 521 flame length | Flame length and radiation distances |
| Pool and tank fire | Solid flame: Thomas, AGA tilt, Mudan emissive power | Radiation distances, burn duration, cooling water, boilover time |
| Flash fire | Cloud envelope to a part of the LFL | Reach, width, area and duration |
| Vapour cloud explosion | TNT equivalence (Kingery-Bulmash curve), TNO Multi-Energy (strength chosen or by GAMES), Baker-Strehlow-Tang | Overpressure against distance |
| BLEVE | CCPS fireball, Eisenberg or TNO probit, burst energy of the vapour (Brode) and the flashing liquid (CCPS) | Fireball size, fatality distances, blast and fragment range |
Examples of the answers it gives
These figures are from the reference cases used to check the application. They show the kind of result, not a result for your site.
| Case | Question | Result |
|---|---|---|
| Methane leak, 100 kg/h, 5 m/s class D | How far is the gas still flammable? | LFL at 3.4 m · 5,660 ppm at 10 m |
| The same leak, ignited | How long is the jet flame, and where is 4.7 kW/m²? | 2.8 m flame · 2.2 m from its middle |
| Gasoline pool fire, 10 m across | How tall is the flame and how hard does it radiate? | 15.8 m · 56 kW/m² at the surface |
| Chlorine, 100 ppm for 30 min | What share of people exposed would not survive? | probit 3.31 · about 4.6 % |
| Propane vessel BLEVE, 10 t | How big is the fireball, and how long does it last? | 125 m across · 9.7 s · 292 kW/m² |
| 1 t of propane, TNT equivalence | What is the equivalent charge? | 297 kg TNT · Z = 15 at 100 m |
What it is not for
- Use it to screen and to check, not as the final basis for design, siting or emergency plans.
- It gives consequences, not risk. It has no leak frequencies, ignition probabilities or population data.
- It assumes flat, open ground. Buildings, terrain and congestion are not modelled, except as a class or a flame speed in the explosion methods.
- Dense-gas results give distances but no cloud width.
- Some library values and curves are supplied as starting values and are marked "verify". Check them against your own references first.