September 2024 | AIChE

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September 2024

Directional Incident Outcome

An incident outcome whose consequences produce an effect zone determined by a given wind direction.

Directional Probability

Probability in a given wind direction.

Dispersion Coefficient

The standard deviation s in a specified direction of the Gaussian distribution model used in atmospheric dispersion. The dispersion coefficient is normally expressed as a function of distance for a given weather stability.

Dispersion Models

Mathematical models that characterize the transport of toxic/flammable materials released to the air and/or the water.

Disproportionation

A chemical reaction in which a single compound serves as both oxidizing and reducing agent and is thereby converted into a more oxidized and a more reduced derivative; e.g., a hypochlorite upon appropriate heating yields a chlorate and a chloride.

Distributed Control System (DCS)

A system which divides process control functions into specific areas interconnected by communications (normally data highways), to form a single entity. It is characterized by digital controllers and typically by central operation interfaces. Distributed control systems consist of subsystems that...

Diversity

The performance of the same overall protective function by a number of independent and different means.

Domino Effects

The triggering of secondary events, such as toxic releases, by a primary event, such as an explosion, such that the result is an increase in consequences or area of an effect zone. Generally only considered when a significant escalation of the original incident results.

Dose

Time-integrated concentration

Dow Chemical Exposure Index (CEI)

A method, developed by The Dow Chemical Company, used to identify and rank the relative acute health hazards associated with potential chemical releases. The CEI is calculated from five factors: a measure of toxicity; the quantity of volatile material available for a release; the distance to each...

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