Name Acronym Description

An inverter (or power inverter) is an electronic device or circuitry that changes direct current (DC) to alternating current (AC) or vice versa


The process by which a neutral atom or molecule acquires or loses an electric charge. The production of ions.

Ionising radiation

Radiation that produces ionisation in matter.


An event where matter has been externally subjected to ionising radiation.

Jaw thrust

A professional technique used on a casualty, especially if there is suspected spinal injury, to open their airway

Joint Decision Model JDM

A decision model presented within the JESIP joint Doctrine and used to make analytical decisions

Joint Dynamic Hazard Assessment JDHA

An assessment of risk taking into account the requirements of all emergency response organisations present at an incident

Joint Service Co-ordination Group

Military body responsible for formal liaison (civil-military and tri-Service) within an Army Regional Brigade’s area

Ladder fuel

Fuels that provide vertical continuity that allow fire to move through the vertical fuel arrangement

Laminar flow

The fastest water travelling with no restrictions in a straight line down a river

Last known position LKP

During a search, clues will be gathered about the person. Occasionally, the clue will be solid enough to be reasonably certain the search subject left it. Since the LKP is more recent than the PLS, this provides a new starting point for the search.


This is any liquid that, in the course of passing through matter, extracts soluble or suspended solids or any other material through which it has passed.

Lifeboat Operations Manager

Person with overall responsibility for a RNLI lifeboat station

Line blocked

This is a rail term for the line being blocked and is a stronger term than requesting trains to be stopped.


Member of the aircrew (civilian or military) who is in charge of planning and distributing cargo and passengers on an aircraft

Local emergency planning groups

Known as:
Local resilience forums (England and Wales)
Regional or local resilience partnerships (Scotland)
Emergency preparedness groups (Northern Ireland)

Lower explosive limit LEL

Lower explosive limit is the lowest concentration of vapour/gas in air at a given pressure and temperature that will propagate a flame when exposed to an ignition source.

Major Accident Hazard Pipeline(s) MAH
pipelines; MAHP(s)

Supply systems for dangerous fluids as defined in schedule 2 of Pipeline Safety Regulations, which include high pressure natural gas, other gases, oils and chemicals

Machine-made mineral fibres MMMF

A wide range of materials that use the inherent strength and durability of woven fibres bonded together with resins. Previously known as Man-made mineral fibres

Manual in-line stabilisation

Maintaining the head and neck of an unconscious casualty in neutral alignment

Marine Response Centre MRC

Maritime and Coastguard Agency co-ordination centre for oil pollution incidents at sea that require a national response

Maritime Incident Response Group MIRG

Specialist fire and rescue service teams strategically located around the country, for response to emergencies at sea

Maritime Patrol Aircraft MPA

Long range military aircraft for detecting, locating, tracking, observing and, if necessary, attacking surface vessels and submarines

Maritime Rescue Co- ordination Centre MRCC

Her Majesty’s Coastguard regional centre overseeing and co-ordinating the search and rescue operations within a region

Maritime Rescue Sub Centre

Her Majesty’s Coastguard unit subordinate to a Maritime Rescue Coordination Centre