GASTEC gas detector tubes are thin glass tubes with calibration scales printed on them so you can directly read concentrations of the substances (gases and vapours) to be measured. Each tube contains a particulate matrix (e.g. silica gel, alumina) which binds carefully selected and highly stable detection reagents that are especially sensitive to the target substance in order to produce a distinct layer of colour change. The tubes are hermetically sealed at both ends.

Today over 600 types of target gas can be measured.

The handy design GASTEC GV-100 cylinder pump, with an inner capacity of 100mL, weighs only 240g. It is designed for use with almost all GASTEC short-term quick-measuring detector tubes.

In Japan, there initially were no designated industrial standards for detector tubes besides industrial standard JIS M 7605/JIS M 7650 for carbon-monoxide detectors (originally developed to ensure mining safety) and certain other standards pertaining to specific gas analysis (e.g. exhaust gas measurement, or for impurities in compressed air or household gas in pressure cylinders, etc.) that also apply to certain detector tubes. It was not until 1985, that a comprehensive standard that regulates detector tubes was established: JIS K 0804. This standard applies to all concentration (%) based measuring equipment for use in work environments (so it is not limited to detector tubes) and is unprecedented in its comprehensiveness.

Of course, there exist many other standards pertaining to detector tubes, for instance, British standard BS5343, German standard DIN33882 or the international standard of IUPAC (International Union of Pure and Applied Chemistry). However, these all deal primarily with the immediate working environment and do not go so far as the JIS standards in regulating actual process control. The following table provides an overview and comparison of the aforementioned standards.

GASTEC detector tubes satisfy the quality standards and norms in the world.

The SEI certification program is well known as one of the most stringent certification programs. We are proud of having the highest number of SEI certified detector tubes worldwide.
SEI：Safety Equipment Institute(U.S.A)

SEI stands for Safety Equipment Institute, a private nonprofit organization established in 1981 in the USA to administer the first non-government third-party certification program for testing and certification of a broad range of occupational safety and protective products. In 1986, it established a national certification system for detector tubes which succeeded and enhanced the existing NIOSH (National Institute for Occupational Safety and Health) certification program. The SEI certification program is accredited by the American National Standards Institute [ANSI] and utilises the ANSI／ISEA l02 American National Standard for Gas Detector Tubes - Short Term Type for Toxic Gases and vapours in Working Environments.

The certification process is stringent and objective as the examination and auditing process for the products and manufacturing facilities is conducted through independent third-parties who are specialists in the field. Currently SEI certifies 21 detector tubes for 21 types of gases/vapours.

1. Four point indication accuracy of gas concentration is required: +/-35% at 0.5 x the testing standard concentration and +/-25% at 1 x, 2 x, and 5 x respectively. The TLV (Threshold Limit Value) of the American Conference of Governmental Industrial Hygienists (ACGIH) is designated as the testing standard concentration.
2. The length of the discolouration (i.e. colour stain) for the designated concentration should be at least 15mm with a maximum standard deviation of 10% permissible in the values as read by three different individuals.
3. Any slant (inclination) of the discolouration (i.e. colour stain) tip should not exceed 20%.
4. Any void or notch between the detection reagent and the matrix holding it in place should not exceed 2mm.
5. The intake (aspiration) capacity of a gas sampling pump should be within a standard deviation of +/-5% of the requirement. Any leakage should not exceed 3% per minute.
6. In addition, the content of any instruction sheet(s) or label(s) for the product in question are stipulated.

The acronym NIOSH stands for the National Institute for Occupational Safety and Health (of the United States). In 1972, NIOSH established what is widely considered to be the world’s first official national certification system for detector tubes. In fact, this groundbreaking initiative to bring clarity to the disparate maze of certification norms and procedures relating to detector tubes by creating a unified certification basis (including on-site manufacturing facility quality-assurance auditing standards) was the precursor of the SEI certification for detector tube systems.

Both long-term measurement and direct colour-change reading/comparison detector tubes (as well as the ancillary sampling pumps) for a total of 23 types of target gases/vapours were subject to certification/testing after which all approved and certified products were officially publicised. During eight years of certification testing, 63 types of detector tubes successfully passed the NIOSH requirements and were officially certified (NIOSH certification ended in 1983). The effectiveness and efficiency of the NIOSH certification program is evident from the fact that only four (4) of 23 tested detector tube types were actually certified in the pre-NIOSH period.

Most widely used in the world for gas detector tube systems. Sample air is aspirated (drawn) into the detector tube manually by pulling the handle of the sampling pump (that the detector tube is inserted in). It can be easily and quickly used by anyone anywhere.

Used for some gas detector tube systems. The air sample is first drawn into a syringe before being injected into the detector tube. There are numerous high-concentration measuring applications of this type available for carbon dioxide, propane, etc.

Used for both gas detector tube systems and sensor systems. Sample air is automatically aspirated by the motor driven pump at a prescribed rate for a prescribed time. The GASTEC GSP series automatic gas samplers use this method.

This system is used to measure compressed air/gas from a compressor or other pressurised vessel. The compressed air is sampled by attaching a pressure reducing valve with flowmetre (between the vessel and the detector tube) in order to enable the pressurised air/gas inside the vessel to flow via the flowmetre into the detector tube at a fixed rate of flow for a predetermined time. It can be used to check for impurities in scuba-diving tanks or pressurised gas containers.

This method is used for some gas detector tube systems as well as sensor systems. Air is not aspirated by sampling pump but allowed to diffuse into a sensor or detector tube placed in a factory or laboratory environment . A diffuser accelerates the gas diffusion rate to produce a longer colour change layer and the mean value for a 1-10 hour period is obtained. GASTEC passive dosimeter tubes utilise this principle.

When a solution is put in a sealed container, any substances dissolved in it vapourise and diffuse until the concentration remaining in solution and the vapour equilibrate at a specific ratio that is unique to that substance: its specific vapour-liquid equilibrium.

To obtain the true concentration of the target substance in solution, simply draw the air into an appropriate detector tube with the GV-100 Gas Sampling Pump and read, and then either:

a.) multiply the reading by the correction factor unique to the specific target substance

 or

b.) correct the reading by using the correction graph for the target substance.

A specific reagent is added to the sample to change the target substance into a gas that is easy to measure. A sample of generated gas is aspirated into an appropriate detector tube with the Model GV-100 Gas Sampling Pump. Tube readings should be corrected by multiplying by prescribed factors that are in a known proportionate ratio to one gram of said reagent.

This method utilises capillary action which causes a sample liquid to rise up a narrow detector tube. With this method, measurements are quite simple.

The detector tube end is merely immersed vertically in the liquid sample (directional arrow pointing upward) and a reading is taken after the prescribed sampling time has elapsed. The GASTEC lineup includes a dissolved sulphide detector tube which can be used to detect sulphur ion (S^2-) in water.

This method entails the forced sampling of a liquid using a strong aspiration (suction) via a syringe with a filter and then extracting it with a dropper pipette through a detector tube. Using the indicated value (that is read) and a prescribed calculation factor the volume of the target substance contained (in the liquid sample) can then be extrapolated. This method is useful, for instance, when measuring the salinity of raw concrete or bulk aggregate.

As the emphasis shifts from mere detection to precise measurement on the ppb (parts per billion) or 1/1000ppm scale, the users demand even better performance and the highest quality from their detector tube systems.

To satisfy these demands, GASTEC utilises a strict and comprehensive quality assurance program that involves all corporate levels from the planning and development to the production and inspection departments. Each department has its specific and stringent standard, and only products that have met all these standards are shipped.

The four essential features of GASTEC’s program are:

A precise standard calibration gas ensures precise measurements

Precise calibration is the lifeline of a detector tube. GASTEC takes particular pride in the painstaking care it takes to keep any concentration fluctuations due to possible adherence of gas molecules to the inside of the storage or transfer vessels to an absolutely insignificant minimum. GASTEC is always on the cutting edge of new developments and technologies as it was quick to adopt innovative and accurate calibration gas generating methods such as the permeation tube or the gas diffusion tube principles. GASTEC is highly regarded also as a pioneer of calibration gas technology.

1. fluctuations in the inner diameters of detector tubes, densities of filling reagents, or sensitivities of reagents
2. the operators who read the tubes

1. leakage of sampling pump
2. incorrectly calibrated detector tubes
3. incorrect sampling time, inappropriate storage or usage of detector tubes
4. presence of interferents

1. Direct reaction
   The target substance (to be measured) directly reacts with a detecting reagent
2. Compound reaction
   The target substance instantaneously reacts with several detecting reagents within the detector tube
3. Two-step reaction
   The substance is oxidised in the pretreatment layer before reacting with the detecting reagent itself

1. Effects on reaction rate:
   Generally chemical reaction rates are proportional to the temperature.
   As a rule of thumb: the lower the temperature falls, the slower the reaction rate becomes; and the higher the temperature, the quicker the reaction rate. Therefore, the occurrence of phenomenon (I.) (II.), can exert quite the opposite effect on the values indicated by the same detector tube type. Some of the GASTEC tube types susceptible to such influences are 6L, 13, 132M, 141.

   (1)	When the temperature is lower than 20ºC (68ºF): Reaction will be slower and part of the sample will not react in the zone where reaction usually occurs at 20ºC (68ºF); but, a slight reaction may instead occur deeper in the tube. As a result, a longer stain of pale colour change is produced, giving a higher indication (i.e. reading).
   (2)	When the temperature is higher than 20ºC (68ºF): Reaction will be quicker and accelerated so the sample may react ahead of the zone where reaction usually occurs at 20ºC (68ºF) in the tube. As a result, a shorter, albeit more intense, stain of distinct colour change is produced, giving a lower indication (i.e. reading).

2. Effects on physical adsorption:
   Generally the quantity of physical adsorption of a certain substance to its reagent is inversely proportional to the temperature. At lower temperatures, some quantity of the substance will be physically adsorbed to the reagent that has already reacted with the preceding substance, and will not reach the usual reaction zone. As a result, only a short stain of colour change is produced, giving a lower indication. On the contrary, at higher temperatures, higher indications will be obtained. Some of the GASTEC tubes thus affected are 1La, 100B, 171.

1. When the detector tube uses a water-based reactant
   The reactant in the reagent matrix in the detecting tube is generally in the form of a water-based solution. In this case, the target gas and the reactant interact in an "air-liquid reaction" and although the resultant water vapour may dilute the concentration of the reagent, there is no adverse effect by humidity on the value indicated by the detector tube because the reactant remains in its liquid state and the absolute mass is not affected either.
   Typical water-based reactant detector tubes are 1LA, 2L, 4LL, 5LB, 8LA, 9LA.
2. 2 When the detector tube uses concentrated sulphuric acid or a desiccant
   When the detector tube uses concentrated sulphuric acid as an oxidant, or when it contains a desiccant, water vapour tends to be absorbed so there is no adverse effect by humidity on the value indicated by the detector tube.
   Some of these detector tubes are 1H, 13, 14M, 71, 91, 122, 132L.

1. The reagent(s) will also react to interferents, giving a higher indication. An example of such an interferent is Hydrogen Sulphide to the Hydrogen Cyanide detector tube (No.12L).
2. If a pH indicator is contained in the tube, acids and bases will react as interferents, giving a higher indication. An example of such an interferent is Hydrogen chloride to the Hydrogen cyanide detector tube (No.12L).

1. When the substances that result from the chemical reaction are identical to the target gas, a higher value (than the actual concentration) will be indicated.
   An example of such an interferent is tetrachloroethylene to detector tube 132L.
2. Because the oxidant reacts with the interferent, the inherent oxidation rate is insufficient, and the indicated value will be lower.
   An example of such an interferent is aromatic hydrocarbons to detector tube 132L.

In principle, the accuracy of detector tubes can be maintained for a longer time in low temperatures; we recommend dark refrigerated storage at 0 to 10゜C (32 to 50゜F) and direct sunlight should be avoided at all times. Be sure to always keep them in a safe place out of the reach of children's eyes and hands.

Detector tubes contain chemical reagents that may include substances subject to laws and regulations requiring specific disposal procedures.

Therefore, a detector tube that has been used (or whose expiration date has passed) should be disposed of in accordance with the relevant disposal regulations valid in your area or jurisdiction. For further information contact your local distributor or GASTEC representative.