Nowadays there is a great concern about accidental releases of Toxic Industrial Chemicals (TIC), such as ammonia or chlorine, into the atmosphere. These TIC are often quoted as the most hazardous materials for three main reasons:

1) They cause health effects at relatively low concentrations.

2) They are stored and transported as pressurized liquefied gases in large quantities.

3) They quickly evaporate when released into the atmosphere.

Because of the statements 2 and 3, releases of Toxic Industrial Chemicals into the atmosphere usually lead to the formation of a dense gas cloud containing a mixture of liquid droplets and gas. The complex interactions between the two-phase dense cloud, the atmospheric turbulence and eventual obstacles around the release pose modeling challenges.

This paper describes new models implemented in the CFD tool FLACS for a better prediction of the physics and phenomena in connection with dense aerosol gas clouds around buildings. The dispersed phase and the continuous phase are assumed to be in dynamic and thermodynamic equilibrium. This is a limiting case which could only accurately represent a cloud consisting of small drops. Special emphasis is held on the modeling of the impingement of the two-phase release on obstacles and subsequent pool generation. Some validation against experiments from the FLIE project (Flashing Liquids in Industrial Environments) will also be presented (impinging jets of propane and butane on walls).