Alarm set point

The selected gas concentration level where an alarm is activated/triggered.

Asphyxiant gases

Gases that are heavier than air and displace it. Asphyxiant gases cause suffocation.

Bump test

Calibration

Exposing and adjusting a sensor to a gas with a known concentration.

Calibration gas

A reference gas or mixture with known or certified content. Used for verification and adjustment of analytical gas sensors.

CBT (Computer Based Training)

Gas safety is part equipment, part training. An onboard computer-based training program allows all crew members to receive proper training, covering operation of instruments, evacuation procedures, and first-aid competence.

Combustible gases (EX gases)

Gases that combust or explode when exposed to heat and oxygen. The fire triangle consists of fuel, oxygen, and heat. The combustible gas represents the fuel.

Consumables

Spares that need to be changed on a regular basis to maintain continuous operation.

Dew point

Hot air can hold more water than cold air. As air cools, its ability to hold water is reduced. When the air is saturated with water vapour at 100 percent relative humidity, dew starts to form.

Diffusion

The flow of a substance, liquid or gas, from a region of high concentration to a region of low concentration, driven by random molecular motion.

Direct indicating tubes

Pre-calibrated detection tubes for gases based on a qualitative colour change and a readout scale for quantification.

EC (Electrochemical sensor)

Primarily used for toxic gases such as H2S and CO in the ppm range.

Enclosed space

Any space that is not open or ventilated to the atmosphere. Even top-open spaces may effectively be enclosed if they contain asphyxiant gases that cannot escape upward.

Explosive gases

See combustible gases. Explosive gases are combustible and highly reactive, producing rapid expansion due to heat generation.

Expiry date

The date when a spare should be replenished.

Gas cylinder

A canister that contains gas.

Gas measuring instruments

Instruments with one or more sensors that detect and quantify gas levels.

Head space (ullage)

The unfilled space between liquid cargo and the roof of a tank. Depending on the cargo, this space may contain explosive or toxic gases.

IGS (Inert Gas System)

A system that fills an enclosed space with an inert gas to prevent explosive atmospheres.

Inert gas

A non-reactive gas that prevents combustion by diluting or removing oxygen from the fire triangle.

Inerting

The introduction of an inert gas to ensure safe, non-reactive conditions.

Instrument report

A vessel’s documented setup of gas detecting instruments and equipment.

IR (Infrared sensor)

Used for combustible gases in the percent volume range, in air and inert gases.

LEL (Catalytic combustion sensor)

Used for detection of combustible gases in the Lower Explosive Limit range in air.

LEL (Lower Explosive Limit)

The lowest gas and air concentration that enables combustion. Below this level, combustion cannot occur.

On-board calibration

Calibration performed onboard the vessel. Eliminates the need for duplicate sensors and off-vessel calibration logistics.

OS (Oxygen sensor)

Galvanic cell sensor used for detecting oxygen levels in percent volume.

Oxygen deficiency

Any oxygen concentration deviating from 20.9 percent by volume. Such environments pose acute or long-term health risks.

Personal gas detector

A portable gas detector carried by individual crew members.

PID (Photo Ionization Detector)

Used for detecting toxic gases in the ppm range, in air and inert gases.

Portable gas detector

A gas detector used to monitor areas beyond the reach of a personal detector, typically equipped with pump and hose for sampling.

ppm (parts per million)

A unit used to denote very small concentrations of a substance.

Purge (gas freeing)

The removal of gas from a confined space using natural or mechanical ventilation.

Regulator

Controls gas flow from a cylinder to a gas detector.

Sampling

The method of bringing a gas sample to the detection device.

Standardised gas detection system

A complete, outsourced gas safety solution including instruments, routines, training, and logistics, ensuring compliance and operational safety.

Support agreement

A vessel’s plan for the delivery of consumables based on the instrument report.

Tank entry

Entry into a tank following a strict safety routine involving gas detection, purging, inerting, ventilation, and continuous monitoring.

TCD (Thermal Conductivity Detector)

Used for detecting combustible gases in the percent volume range, in air and inert gases.

TLV-STEL (Threshold Limit Value, Short-Term Exposure Limit)

A 15-minute exposure limit that should not be exceeded during a workday, even if the 8-hour average is within limits.

TLV-TWA (Threshold Limit Value, Time-Weighted Average)

The average exposure limit over an 8-hour workday and 40-hour workweek believed to be safe over a working lifetime.

Toxic gases

Gases that cause poisoning through inhalation, ingestion, or skin absorption. Toxicity depends on concentration and exposure time.

UEL (Upper Explosive Limit)

The highest gas and air concentration that allows combustion. Above this level, combustion cannot occur.

VOC (Volatile Organic Compounds)

Substances that evaporate rapidly at room temperature. Many VOCs are toxic, such as benzene.