Special Sale Price!!! - For a limited time, when you purchase a single user license of CHARM, you'll receive a 1 year subscription to WebCHARM and a seat at one of our upcoming CHARM training courses.  All at no additional cost! Modeling The potential for accidental release of hazardous chemicals, fires, and explosions, poses a risk that must be addressed on several levels. The EPA Risk Management Program (Rule 112r) requires hazard assessment and emergency response programs. To assure that you have adequate resources and that plans are well organized for any contingency, you need to plan for emergency response. Should such an accident occur, you need real-time data to guide the response activities. CHARM software helps you meet all of these needs.

Input

Planning Mode
CHARM software can be run in planning mode where the release scenario is described through text input.

In the planning mode, CHARM software guides you through a list of scenarios that describe a particular release and the present meteorological conditions. When you select the Plume display, CHARM software requests a release time to use in the calculations. This enables a simulation of the release. The various graphic displays can be altered with a variety of options, and the release information can be stored in a scenario file for use with CHARM software's emergency response mode.

Emergency Mode
After the Planning Mode is used, the CHARM software produces an emergency response. based on a number of scenarios of potential releases stored earlier. These scenarios are linked with icons on a map. You can define maps with the CHARM Editor for use in CHARM displays. This makes graphical input available.

In the emergency response mode, CHARM software quickly accesses stored input in one or more scenario files. To save time in an emergency situation, CHARM software enables you to define and store a base map that will be displayed automatically whenever the CHARM program is started. The map display has icons that can be selected to show release scenarios and other maps.

CHARM software generates plume displays, radiation and overpressure footprint displays, plots, tables, and site information. Emergency response procedures for a particular chemical release, local sources of help, and important phone numbers stored in the planning mode can be retrieved quickly in the emergency response mode.

Source Term

With the CHARM source term, you can specify the design, control, and mitigation measures applicable to the source. If the initial model results indicate an unacceptably high consequence, you can use CHARM software to hypothesize what the impacts might be with other designs and mitigation measures. This can allow you to better estimate the impact reduction that an investment in risk reduction might achieve.

CHARM software has three selections for source terms

• Container/Surface Description
• Pool/Surface Description
• User Specified

The Container/Surface Description allows for liquid/vapor to escape from a container. The release is assumed to occur over four stages. The liquid which releases can flash, form droplets, or form a pool. The pool can grow over time to a given maximum size or to a size where the evaporation rate is equal to the mass addition rate. You can specify the time that it takes for material to get out of containment (e.g., 10 minutes) and CHARM software calculates a required hole size.

The Pool/Surface Description allows a static pool to evaporate.

In Container/Surface and Pool/Surface Description CHARM software calculates all parameters of the release: emission rate, temperature, phases, etc. The User Specified mode lets the user enter these values directly. Normally, the User Specified entries are variations on the CHARM software results from the Container/Surface or Pool/Surface Description calculation.

A mitigation time can be entered for the release from containment and pool evaporation. The release is assumed to stop after the mitigation time is reached. In the User Specified mode a release duration is input.

The results from the source calculation are available in tabular and graphical form.

Algorithms

For dispersion of a release in the atmosphere there are three algorithms used. The model, using the currently calculated parameters of a release, internally decides on the use of an algorithm. The algorithms cover: the jet phase of the release (all densities), the gravitational spread when a denser-than-air cloud is on the ground, and all other cases (e.g. not denser-than-air on ground and aloft clouds).

The fire algorithms calculate the thermal radiation impact from BLEVEs, Jet Fires or Flares, and Pool Fires. For Jet and Pool Fires effects such as flame tilt are calculated.

Two forms of explosion are allowed: Mechanical Failure and Vapor Cloud Explosions. A Mechanical Failure simulation assumes a pressurized containment vessel fails instantaneously, releasing a pressure wave. The Vapor Cloud Explosion algorithms can handle deflagration and detonation.

Output

You can display a large number of graphs and tables in CHARM software. CHARM software calculates impacts of concentration, thermal radiation, and overpressures. The thermal radiation can be from pool fires, jet fires, or BLEVE/fireballs. The overpressures can be calculated for vessel failures and vapor cloud explosions.

The population impacted by any footprint (concentration, radiation, or overpressures) can be estimated using US Census Bureau data. This feature can meet EPA RMP protocol requirements for population impact estimates.