Glossary of terms used on this site

A procedure to ensure that a gas detection instrument responds correctly to gas hazards.

A quantity of gas that is designed to calibrate a gas detector instrument. Calibration gas contains a precise and guaranteed concentration of one or more compounds. There are instruments to automatically calibrate one or more gas detectors, registering every bump test and calibration action to rigorously monitor the state of the gas detection equipment in use.

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CO2 is a gas that occurs naturally in Earth's atmosphere. It is a product of the burning or corrosion of any carbonic compound. It is 60% heavier than dry air, making it an asphyxiant in confined spaces. It has a distinct odour that is only apparent at hazardous concentrations of over 3.9% by volume. CO2 is absorbed by plants to form carbohydrates through photosynthesis, releasing oxygen into the atmosphere. It is one of the greenhouse gases. CO2, although not toxic per se, is still considered a hazardous substance because of its propensity to replace ambient air, lowering oxygen levels. Lower oxygen levels are associated with concentration problems, headaches and general feelings of discomfort, even at concentrations below 1% by volume. This makes it important to monitor CO2 levels in places where people gather in poorly ventilated rooms, such as class rooms. CO2 is measurable through colorimetric detection tubes and specialized infrared sensors. Special models for class room use exist to alert occupants of the need to ventilate the room.

A highly toxic, flammable, colourless, odorless gas that is predominantly a product of incomplete combustion, and produced on a large scale as a precursor for the production of many other compounds. Carbon monoxide is detectable with colorimetric detection tubes and dedicated electrochemical cells. It is not detectable using a PID instrument. A carbon monoxide sensor is optional in almost all gas detectors with space for electrochemical sensors. Care should be taking with the carbon monoxide electrochemical sensor, as it is generally very cross-sensitive to most carbohydrates. An activated carbon filter is used to circumvent this cross-sensitivity, but that filter wears out even when not in use, by which time the instrument will report false-positives on carbon monoxide.

A material that increases the rate of a chemical reaction while not being consumed by that reaction.

A sensor that contains two heated coils, connected by a Wheatstone bridge. One of the coils is treated with a catalyst to aid combustion. When a combustible gas passes through, the temperature increases at the catalyst-treated coil, changing the conductivity of that coil, causing a potential difference at the Wheatstone bridge. Measuring the change in potential difference enables the instrument to indicate the risk of explosion. A mesh filter is used to protect hazardous atmospheres from ignition. Gas has to permeate this mesh filter. Larger molecules have greater difficulty passing through the mesh filter, increasing the response time. Also, some gases burn hotter than others. LEL sensors are typically calibrated for methane, correction factors have to be applied for other gases.

Upper limit of an employee

Scale for measuring temperature that originated with Anders Celsius in the 1700s. Defined by the temperature at which water freezes (0

A printed certificate that shows a quantity of gas with a precisely specified mixture to conform to the stated mixing ratio.

A highly toxic, flammable, pale yellow gas with a sharp pungent smell. Chlorine attacks the respiratory system, eyes and skin. Denser than air, it tends to accumulate at the bottom of poorly verntilated spaces. Chlorine gas is a strong oxidizer, making it an essential compound in many industries. Chlorine is detectable with colorimetric detection tubes and dedicated electrochemical cells.

Glass tubes through which a gas sample is drawn to allow the user to measure various types of gas found in the atmosphere. The tubes contain reagents that filter or bond to non-target gases and reagents that change hue when they come in contact with their target gas. The concentration is given by the length of the color change, as indicated by a printed scale on the outside of the glass tube.

A gas that is held under greater than atmospheric pressure.

Generally defined as an enclosed or partially enclosed environment, with or without restricted access, not designed for the stay of persons. They generally offer limited freedom of movement, limited accessibility and limited escape routes. Confined spaces are generally poorly ventilated and are susceptible to the accumulation of toxic, flammable, asphyxiant or otherwise hazardous compounds. Laws, regulations and best practices demand the confined space to be tested for various hazards before persons may enter, sometimes under the condition of further personal protection equipment. Gas detectors, often fitted with a pump, probe, a length of hose and ball floats, are used to check confined spaces for the presence of oxygen, combustibles and toxic compounds. Also, when working in a confined space, gas detection equipment is used to alarm workers of deteriorating conditions.

An exchange during which a client and an expert engage in a process to find the best solutions for a problem held by the client. 7Solutions is an independent supplier. We work with all manufacturers and we know the market like the back of our hand. Which means we can provide you with the exact quality and characteristics, even the exact brand, you are looking for. Whether you require the technologically advanced or the dependable work horse. Knowing the market like we do enables us to give great advice of which instrument is suitable for any given set of circumstances.

In fixed gas detection, a device to monitor multiple sensors at once and switching alarms or processes as programmed.

Term describing a substance