Atmospheric Unintended Release Analysis
How far can a release reach?
Describe a leak of flammable or toxic material. AURA works out the release rate, the cloud or pool it forms, and the distances to fire, explosion and toxic effects.
From a leak to a hazard distance
Each step feeds the next, and every page shows the equations it used.
The release
Material, pressure, temperature, hole size or rate, tank and level.
Source term
Release rate, flashing, what stays airborne and what falls to the ground.
Pool and cloud
Pool spread and evaporation; dispersion for 2F, 5D or your own weather.
Fire, blast, toxic
Jet, pool, tank and flash fire; vapour cloud explosion; BLEVE; toxic exposure.
Summary and report
Every hazard distance in one table, cloud outlines, a printable report and CSV.
What it models
Each event has a published screening method and a choice of equation of state for the properties.
Release
- Gas or liquid release
- Orifice flow, choked or sub-sonic, with flash and rain-out.
- Draining tank
- Level, rate and mass against time for vertical, horizontal and spherical vessels.
- Pressure vessel and pipe
- Gas blowdown, pipe flow with friction, pipeline rupture and pumped lines.
- Liquid pool
- Spreading to a minimum depth or a bund; evaporating or boiling.
Cloud
- Vapour cloud
- Gaussian plume and puff; Britter-McQuaid for dense gas. Distances to LFL and UFL.
- Toxic exposure
- Toxic load and probit, indoors and outdoors. Distances to IDLH, ERPG and AEGL.
Fire
- Jet fire
- Flame length and distances to 37.5 down to 1.6 kW/m².
- Pool and tank fire
- Solid flame with tilt. Burn duration, cooling water and boilover time.
- Flash fire
- Reach, width, area and duration of the burning cloud.
Explosion
- Vapour cloud explosion
- TNT equivalence, TNO Multi-Energy and Baker-Strehlow-Tang.
- BLEVE
- Fireball size and dose, blast from the burst, fragment range.
Questions it answers
How far could this leak reach, and does it get to the control room?
Put a number on a hazard raised in a HAZID or HAZOP, so the action can be closed, kept or escalated.
Is this tank far enough from its neighbour, the fence and the muster point?
Radiation and overpressure distances for layout and separation.
Which area do we evacuate for a chlorine leak at night with light wind?
Distances to toxic limits and fatality levels for the weather cases you plan against.
How much cooling water does the next tank need?
Radiation on a neighbouring tank, cooling water flow, burn-out and boilover time.
Can this jet fire cause the LPG bullet beside it to fail?
Link a fire to the vessel it threatens and assess the BLEVE that could follow.
Which of these forty scenarios deserve detailed modelling?
Run them all, rank them by hazard distance, and send only the governing ones for detailed work.
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.
- Some library values and curves are starting values marked "verify". Check them against your own references first.