Working with ALOHA

ALOHA is designed to produce results quickly enough to be of use to responders during a chemical emergency response. ALOHA can help responders rapidly assess the scale of a chemical incident--that is, whether the release will travel 10s, 100s, or 1,000s of yards.

To help you get the hazard information you need quickly, ALOHA:

• Minimizes data entry errors by checking the input values and warning you if the value is unlikely or not physically possible. ALOHA also offers default values when possible.
• Contains its own chemical library with physical properties for approximately 1,000 common hazardous chemicals so that you do not have to enter that data.
• Uses calculations that are a compromise between accuracy and speed.

In addition to emergency response, ALOHA's hazard modeling capabilities can also be used for planning, training, and academic purposes.

Using ALOHA to Model a Toxic Gas Cloud, Fire, or Explosion

To model hazards with ALOHA, you must enter the required scenario information (see below). ALOHA's easy-to-use interface guides your through the data entry process using a series of dialog boxes. Detailed help is provided with each dialog box.

Required Inputs

• Enter basic scenario information (such as date, time, and location).
• Choose a chemical from ALOHA's chemical library.
• Enter atmospheric information (such as wind speed and direction, air temperature, and cloud cover) by hand or automatically using a portable station for atmospheric measurements (SAM).
• Choose a source: direct, puddle, gas pipeline, or tank.
• Enter source information (such as release amount, tank dimensions, and whether the chemical is burning).
• Specify the Levels of Concern (LOCs) you want ALOHA to use when estimating the threat zones or use the default LOCs ALOHA offers.
• Choose the type of hazard (such as a toxic vapor cloud or a vapor cloud explosion) you want ALOHA to use when estimating the threat zones.

As you enter information, ALOHA displays key information in a Text Summary screen. Once all of ALOHA's calculations are complete, you can display the results in a variety of graphical outputs (including a threat zone plot).