• One worst case analysis must be conducted for toxic substances and one worst case analysis must be conducted for flammable substances.
• Additional worst case analysis must be conducted if another covered process potentially affects other receptors.

A) Worst Case Release Quantity

• For substances in a vessel, the greatest amount held in a single vessel, taking into consideration administrative controls.
• For substances in a pipe, the greatest amount in a pipe, taking into consideration administrative controls.

B) Worst Case Release Scenario - Toxic Gases

• If the toxic is normally handled as a gas or as an liquid under pressure, assume the release is over a 10 minute period.
• If the toxic is normally handled as a refrigerated liquid, and the release is not contained by any passive mitigation, assume the substance is released as a gas over a 10 minute period.
• If the toxic is normally handled as a refrigerated liquid, and the release is contained by passive mitigation, assume the liquid is spilled instantaneously to form a pool. The release rate must be calculated at the boiling point of the liquid.

C) Worst Case Release Scenario - Toxic Liquids

• Assume liquid is spilled instantaneously to form a pool.
• If no passive mitigation controls are in place, assume liquid spreads to a depth of 1cm. From this you should be able to determine the surface area and the release rate.
• If passive mitigation is in place, use the surface area of the contained liquid to find the release rate.
• If the release is not onto a smooth or paved surface, you can take into account the surface characteristics.
• The release rate must account for the highest daily maximum temperature over the past three years, the temperature of the substance, and if its a mixture, the concentration of the toxic substance.

D) Worst Case Release Scenario - Flammables

• Assume the entire substance vaporizes (explodes) in a vapor cloud explosion.