Gas detector tube systems

A means for measuring the concentration of one or more target gases using a detector tube and a gas sampling pump

Gas sampling pump	A device for aspirating a specific volume of air to be sampled into the detector tube
Vacuum sampling system	By pulling the fully retracted (pushed-in) pump handle, a complete vacuum is created inside the pump cylinder, which in turn aspirates (draws in) the air sample into the attached detector tube
injection	Used for some gas detector tube systems; an air sample is first drawn into a syringe before being injected into the detector tube
Detector tube	Most gas detector tubes are thin glass tubes, with calibration scales printed right on them, so you can directly read concentrations of the target gases and vapours to be measured; each tube contains detection reagents that are especially sensitive to the target substance and quickly produce a distinct layer of colour change
Carrier	The carrier is a matrix in granulated form that preserves the reagent; GASTEC uses silica gel, alumina, celite, silica sand, etc
Filler	This is the general term used to describe a particular chemical (e.g. silica gel, alumina, etc.) in the detector or reaction tube that serves to bind the reagent to the carrier and preserve it; detection reagents, reactants, oxidants, scrubbers, and desiccants, all fall under this category
Detection reagent	This term refers to the chemical within the calibrated portion of the detector tube which reacts with the target gas and discolours, whereby, the existence of the target gas is established
Reactant	A chemical agent that transforms the target gas into a measurable substance
Oxidant	A chemical agent that oxidises the target gas and converts it into a measurable substance
Scrubber	A chemical that removes the effects of any interferents in the gas sample
Desiccant	A chemical additive that removes moisture

Cylinder type	One of the basic types of gas sampling pump
Lip seal	A sealing sleeve that is used on the adhesion surface of a cylinder and piston; it resembles a lip and is extremely airtight (hence, it is called a lip seal)
Rubber inlet flange (the opening for inserting/attaching the detector tube for measuring)	This refers to the rubber flange portion of the sampling pump’s inlet port which holds the detector tube in place
Stuffing	Stuffing material (which is tightly packed into both ends of a detector tube) prevents the content of the tube from becoming loose or dislodged. GASTEC uses polyethylene, glass wool, as well as other material

Calibration range	The calibrated concentration range which is printed on the detector tubes and can be directly read to determine the concentration value of the target gas (after the standard number of sampling strokes has been completed)
Sampling range	The maximum range in which sampling (i.e. measuring) is possible with a certain detector tube; it often involves changing the number of pump (sampling) strokes; by doing so the sampling range can be extended beyond the calibrated scale on the tube
Detection limit	The lowest threshold of target substance concentration that can be detected with the individual detector tube; it is only barely detectable with the naked eye through a slight discolouration (at the entry to the detection agent area)
Sampling time	The time that should be allowed to ensure full completion of one pump stroke (aspiration)
Measuring time	The time required from commencement of sampling time (pulling the handle for the first pump stroke) and attempting to read the calibrated scale: Measuring time = the amount of time (required to complete one pump stroke [aspiration]) x number of pump strokes
Discolouration	The change in colour of the detection agent due to the chemical reaction
Term of validity	The period for which the accuracy of a detector tube is guaranteed, provided that it is stored correctly (in accordance with the storage instructions)
Correction method	A method for correcting any measurement/reading for any accuracy-affecting external factors
Calibration gas	A gas of known concentration level(s) that is used to set (calibrate) or correct (recalibrate) detector tube or sensor based gas measuring systems
Volume (of sampling pump)	The amount of air that can be aspirated (drawn) into the gas sampling pump
Indication accuracy	There are two evaluation methods for indication accuracy: (1) When the spread in indicated values is to be evaluated the coefficient of variance (CV) is used (2) When overall evaluation of both the accuracy of the indicated values is intended, the standard deviation (in %) is used
Slanted tip of discolouration	The tip of the discolouration in a detector tube should be slanted after sampling/measurement is completed
Slanted tip of detection agent	The entry portion (zero point) of the detection agent should be slanting
Deviation (error)	The difference between the indicated value(s) of a detector tube and the true concentration
Spread	When rather than being concentrated within a narrow range, the indicated values (or their mean values) extend across a broad range
Number of pump strokes	The number of times the (fully retracted) gas sampling pump handle is pulled out in order to aspirate (draw) a gas sample into a detector tube
The standard number of pump strokes	Indicated value = This defines the number of pump strokes necessary for direct reading of the value(s) indicated on a detector tube (without any corrections, adjustments or calculations being necessary)

Length of discolouration	The target substance’s concentration is determined by the length of the discoloured layer in the detector tube (the longer the discolouration the higher the concentration); GASTEC detector tubes belong use this principle
Direct reading	Detector tubes with calibrated scales printed right on them allow the target gas concentration(s) to be “read directly”; it was GASTEC who pioneered this type of tube in Japan
Discolouration (layer) length	The length of the reagent layer that discolours when the detection agent in the detector tube reacts with the target substance
Calibration curve	Indicates the relationship between the concentration of target gas and the discolouration (layer) length; it is used to accurately calibrate the detector tube
Zero point	Zero is calibrated (printed) on the detector tube at the point from where the detection agent is filled in
Indicated value(s)	The value indicated by reading the tip of the slanted discolouration in the detector tube

Matter	Anything of finite mass that occupies space is called “matter"; and any such substance can be found in any of three basic states: gas, liquid, and solid; depending on such factors as chemical composition, temperature, pressure
Gas	A gas is a phase of matter which expands indefinitely to fill any containment vessel; it is characterized as having a low density
Liquid	A liquid is a phase of matter which at standard temperature is free to conform to any shape of vessel but has a fixed volume as well as a greater density than a gas
Solid	A solid is a phase of matter characterized by a definite volume and shape, for instance: a metal, or quartz; moreover, a solid resists external forces to change its shape
Air (gas) Sample	This refers to the “air” that is extracted, or “sampled” in order to determine the target gas(es)’ concentration in it during environmental measurement of gas (usually, for specific chemical experimentation, examination or analysis)
Target gas	The gas whose concentration is to be measured/determined
Corrosive substance	A substance which has the characteristic of substantively deteriorating (transforming) any other substance it comes into contact with
odourous substance	Any substance which which gives off an odour that is generally considered to be unpleasant
Organic solvent	Primarily carbon or hydrogen based organic compounds (frequently having oxygen or halogen atoms as well) which have the ability to dissolve (break down) other substances
Inorganic gas	The term generally refers to gaseous inorganic compounds, which usually have their counterpart of the same name in the organic compounds
Oil mist	Very fine oil particles or droplets that are airborne

Interferent (or interference gas)	An interferent is any gas that will cause a similar chemical reaction in a detector tube than the target gas. This affects the accuracy of the reading
Coexisting gas	A gas, other than the target gas, that is also present in an air/gas sample
Applicable temperature range	This refers to the temperature range in which a gas measuring instrument (e.g. detector tube system) can be operated; it is NOT the ambient temperature of the air sample , but, the temperature of the detector tube and the gas sampling pump, precise, accurate measurements can only be ensured within this range
Temperature compensation/adjustment	Some detector tubes are susceptible to the effects of temperature, in which case the values read off the detector tube, need to be adjusted or corrected accordingly
Humidity compensation/adjustment	Some detector tubes are susceptible to the effects of humidity, in which case the values read off the detector tube, need to be adjusted or corrected accordingly
Atmospheric pressure compensation	Drastic changes in atmospheric pressure, can also affect the accuracy of detector tube readings, so that they need to be adjusted or corrected accordingly

Reaction rate	The rate (speed) at which the quantity of each component substance changes during the course of a chemical reaction
Chemical reaction	The phenomenon in which one substance is transformed into another due to environmental change or interaction(s) with other substances
Deacidification / neutralization	When an acid reacts with a base
Oxidization	In its most basic form oxidation is a chemical reaction with oxygen;essentially, oxidation is a reciprocal process in which one agent is reduced and one oxidised as well as a transfer of electrons occurs.
Generated substance	Any substance that is given off when a substance changes in a chemical reaction with with itself or other substances
Thermal decomposition	When a compound is broken down (decomposed) due to the effects of heat

Short-term measurement	The type of measurement with detector tubes that is conducted according to a fixed volume of sampling (rather than over a certain period of time)
Long- term measurement	The type of measurement with detector tubes that is conducted over a certain amount of time (rather than with a fixed volume of sampling)
Conversion coefficient / Conversion scale / Graph	Additional gases, other than the target gas(es) that the detector tube was designed and calibrated for, can also be measured by the detector tube scale to be multiplied by a conversion coefficient to obtain a value indicative for the alternate gas in question.
Aspiration type sampling	This sampling process entails the use of a pump with which the sample is extracted and aspirated (drawn) into the detector tube
Diffusion type	The system utilising natural gaseous diffusion as the extraction method for the gas sample

QC No.	The GASTEC quality control number printed on every detector tube which is affixed to all products (of the same lot) manufactured under identical (or equivalent) strictly controlled conditions
Filling	The degree of filling in a detector tube (how tightly the reagents are packed into the tube)
Chemical compounding/preparation	The procedure (within the manufacturing process of chemicals including detection reagents, fillers, etc.) for compounding the chemicals to adhere to the carrier
Final inspection	The final inspection phase in which it is assessed and recorded whether the completed detector tube fulfills its stipulated requirements as a product
Periodic inspection	Performance inspection periodically conducted during the term of validity of the detector tube products

Airtightness test	Investigates the airtightness of a gas sampling pump
Storage method	In order to ensure the accuracy of GASTEC products should always be stored as per their enclosed instructions

NIOSH	Acronym of the National Institute for Occupational Safety and Health (USA)
SEI	Acronym for the Safety Equipment Institute (USA), currently the only institute in the world that certifies detector tubes
Quality control system	Any company-wide program or system for quality assurance
Performance requirements	The requirements placed on the performance of a specific product
TLV-TWA	Threshold Limit Value / Time Weighted Average TLV stands for Threshold Limit Value which is the maximum permissible concentration of a substance (usually expressed in parts per million in air) for some defined period of time (usually 8 hours, but sometimes for 40 hours per week over an assumed working lifetime). These values, vary somewhat from country to country, and are contained in laws and regulations to varying extents as well TWA stands for Time Weighted Average which is the common term used in the specification of Occupational Exposure Limits (OELs) to define the average concentration of a chemical to which it is permissible to expose a worker to over a period of time, usually 8 hours
TLV-STEL	Threshold Limit Value/Time Weighted Average TLV-STEL stands for Threshold Limit Value, Short Term Exposure Limit, which is the maximum concentration permitted for a continuous 15-minutes exposure period.

JIS K 0804	Japanese industrial standard (JIS) for gas measuring systems utilizing detector tubes.
JIS M 7650	Japanese industrial standard (JIS) for long-term measurement carbon monoxide detectors.
BSI	Abbreviation for British Standards Institution
DIN	Abbreviation for Deutsches Institut fuer Normung (German Standards Institution)
IUPAC	Abbreviation for International Union of Pure and Applied Chemistry
ANSI	Abbreviation for American National Standards Institute