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Infrastructure
The basic facilities, services, and installations needed for the functioning of a site such as transportation and communications systems, water and power lines, and public institutions including emergency response organizations.
Ingestion
The taking of a substance through the mouth. Importance: A route of exposure to a hazardous material.
Inhalation
The breathing in of a substance in the form of gas, vapor, fume, mist, or dust. Importance: A route of exposure to a hazardous material.
Inherent Safety
A concept or an approach to safety that focuses on eliminating or reducing the hazards associated with a set of conditions.
Inherently Safer
A condition in which the hazards associated with the materials and operations used in the process have been reduced or eliminated, and this reduction or elimination is permanent and inseparable.
Inherently Safer Design
A way of thinking about the design of chemical processes and plants that focuses on the elimination or reduction of hazards, rather than on their management and control.
Inhibitor
A chemical which is added to another substance to prevent an unwanted chemical change from occurring. Importance: Inhibitors are sometimes listed on a MSDS, along with the expected time period before the inhibitor is used up and will no longer prevent unwanted chemical reaction.
Initiating Cause
In the context of hazard evaluation procedures, the operational error, mechanical failure, or external event or agency that is the first event in an incident sequence and marks the transition from a normal situation to an abnormal situation. Synonymous with initiating event.
Injury
Physical harm or damage to a person resulting from traumatic contact between the body and an outside agency or exposure to environmental factors.
Inspection
A work activity designed to determine if ongoing work activities associated with operating and maintaining a facility comply with an established standard. Inspections normally provide immediate feedback to the persons in charge of the ongoing activities, but normally do not examine the management systems that help ensure that policies and procedures are followed.
Inspection, Testing, and Preventive Maintenance (ITPM)
Scheduled proactive maintenance activities intended to (1) assess the current condition and/or rate of degradation of equipment, (2) test the operation/functionality of equipment, and/or (3) prevent equipment failure by restoring equipment condition.
Instrumented protective system (IPS)
A safety system composed of a separate and independent combination of sensors, logic solvers, final elements, and support systems that are designed and managed to achieve a specified risk reduction.
Integral Model
A dispersion model which averages (or integrates) the concentration in a given dimension or time so that concentrations can be described by solving an ordinary differential equation instead of a partial differential equation.
Intentional chemistry
Processing of substances such that a chemical reaction is intended to take place.
Interlock
A protective response which is initiated by an out-of-limit process condition. Instrument which will not allow one part of a process to function unless another part is functioning. A device such as a switch that prevents a piece of equipment from operating when a hazard exists. To join two parts together in such a way that they remain rigidly attached to each other solely by physical interference. A device to prove the physical state of a required condition and to furnish that proof to the primary safety control circuit.
Interlock System
A system that detects out-of-limits or abnormal conditions or improper sequences and either halts further action or starts corrective action.
Intermediate Event
An event that propagates or mitigates an initiating (basic) event during the accident sequence (e.g., improper operation actions, failure to stop an ammonia leak but an emergency plant mitigates the consequences).
Intermediates
Materials from a process that are not yet completely finished product. They may be a mixture or compound.
Internal Boundary Layer
A transition layer rising downwind of a change of surface roughness, which separates the air below, which has adjusted to the new surface, from the air above, which is still influenced by the old upwind surface. The internal boundary layer has an average slope of about 1/100 to 1/10.
Internal Controls
The various engineering and managerial means, both formal and informal, established within an organization to help the organization direct and regulate its activities in order to achieve desired results; also refers to the general methodology by which specific management processes are carried on within an organization. The requirement for management systems and their formal evaluation during an audit are not currently compliance requirements. The evaluation of the adequacy of the internal controls is accomplished using some of the related audit criteria.
Internal Failure
A failure involving either the hardware or the software of the Process Control System, excluding the Application Program.
Interview
Questioning, both formally and informally, facility personnel or other individuals in order to obtain an understanding of the plant's operations and performance.
Intrinsic Property
In relation to materials, a property of the material itself, regardless of use or environmental conditions.
Inversion
In the air quality literature, the term inversion refers to a situation when the actual temperature gradient is positive (i.e., the temperature increases with height).
Ionization
The dissociation of air into ions by means of electrical energy.
Irritant
A substance which, by contact in sufficient concentration for a sufficient period of time, will cause an inflammatory response or reaction of the eye, skin, or respiratory system. The contact may be a single exposure or multiple exposures. Some primary irritant: chronic acid, nitric acid, sodium hydroxide, calcium chloride, amines, chlorinated hydrocarbons, ketones, alcohols. Importance: Knowing that a substance is an irritant allows you to be aware of the signs and symptoms of overexposure.
Isolated (Devices, Circuits)
Devices, Circuits are said to be isolated where there is not galvanic connection between them.
Isomerization
The conversion of a chemical with a given molecular formula to another compound with the same molecular formula but a different molecular structure, such as from a straight-chain to a branched-chain hydrocarbon or an alicyclic to an aromatic hydrocarbon. Examples include the isomerization of ethylene oxide to acetaldehyde (both C2H4O) and butane to isobutane (both C4H10).
Isopleth
A plot of specific locations (in the three spatial coordinates: x, y, z) downwind from the release source that is corresponding to a concentration of interest (e.g., fixed by toxic load or flammable concentration).
Isothermal
A system condition in which the temperature remains constant. This implies that temperature increases and decreases are compensated by sufficient heat exchange with the environment of the system.
Jet Discharge
A release of vapor or aerosol at sufficient pressure that the momentum of the release provides the dominating mechanism for air entrainment and for the centerline trajectory of the release.
Jet Fire
A fire type resulting from the discharge of liquid, vapor, or gas into free space from an orifice, the momentum of which induces the surrounding atmosphere to mix with the discharged material
Job Safety Analysis (JSA)
A procedure that systematically identifies: 1) job steps, 2) specific hazards associated with each job step, and 3) safe job procedures associated with each step to minimize accident potential. Also called job hazard analysis
Job Task Analysis
the analysis phase of the instructional systems design (ISD) model consists of a job task analysis based on the equipment, operations, tools, and materials to be used as well as the knowledge and skills and attitudes required for each job position.
Knockout Pot
A vessel used to separate liquids from vapors.
Knowledge (or Process Safety Knowledge)
Knowledge is related to information, which is often associated with policies, and other rule-based facts. It includes work activities to gather, organize, maintain, and provide information to other process safety elements. Process safety knowledge primarily consists of written documents such as hazard information, process technology information, and equipment-specific information.
Knowledge, Skills, and Abilities (KSAs)
Knowledge is related to information, which is often associated with policies, procedures, and other rule-based facts. Skills are related to the ability to perform a well-defined task with little or no guidance or thought. Abilities concern the quality of decision making and execution when faced with an ill-defined task (e.g., applying knowledge to troubleshooting).
Lagging Indicators
Outcome-oriented metrics, such as incident rates, downtime, quality defects, or other measures of past performance.
Lagging Metric
A retrospective set of metrics based on incidents that meet an established threshold of severity.
Laminar Burning Velocity
See Burning Velocity
Land Use Planning
The control of developments around hazardous installations based upon consideration of the risks posed by the installations, and the nature of the developments and the populations they might contain.
Lap Joint
See "Slip Flange".
Latent Failure
Failure in a component as a result of a hidden flaw.
Law of "Conservation of Energy"
Second law of thermodynamics that states that energy can only change in form, but can never be "lost" or "created".
Layer Ignition Temperature (LIT)
The minimum temperature at which a dust layer will self-heat.
Layer of Protection Analysis (LOPA)
An approach that analyzes one incident scenario (cause-consequence pair) at a time, using predefined values for the initiating event frequency, independent protection layer failure probabilities, and consequence severity, in order to compare a scenario risk estimate to risk criteria for determining where additional risk reduction or more detailed analysis is needed. Scenarios are identified elsewhere, typically using a scenario-based hazard evaluation procedure such as a HAZOP Study.
Layers of Protection
A concept whereby several independent devices, systems, or actions are provided to reduce the likelihood and severity of an undesired event.
Layout
The relative location of equipment or buildings within a given site.
Leading Indicator
Process-oriented metrics, such as the degree of implementation or conformance to policies and procedures, that support the PSM program management system and has the capability of predicting performance.
Leading Metric
A forward-looking set of metrics that indicate the performance of the key work processes, operating discipline, or layers of protection that prevent incidents.