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Gas detection tubes faq

Using colorimetric gas detection tubes and dosimetric detector tubes (dosi-tubes) for detection or gas monitoring is a simple and cost-effective solution. Thanks to these benefits and the wide range of detected gases and substances, they are well known by workers who need more accuracy in their applications.

gas detection tube: colorimetric tubes and dosi-tubes frequently asqued questions


  • what is a gas detection tube?

    Colorimetric gas detector tubes are glass tubes filled with chemical reagents that absorb and react to the measured targeted gas or vapor. A colorimetric stain (color change) appears. The reading of the concentration is made directly on the scale printed on the tube for almost any gas detection tube. This gas detection tube system is composed of an air sampling pump and a detector tube.


  • how does it work?

    Gastec uses a piston pump that injects air through the gas detector tube connected to it. In order to perform gas detection, pull the soft handle located at the end of the sampling pump until the click that indicates the end of the sampling.

  • what is the operation principle?

    Colorimetric and dosimeter gas detection tubes are usually sold in ten unit boxes and are sealed at both ends. During the operation, the ends of the tubes are broken using the built-in tip breaker of the manual sampling pump. Gas detector tubes are designed for use with a portable air-sampling pump. Depending on the manufacturer, these pumps operate through a piston or a bellows system. The tube is connected to the pump and the user samples 50 to 100mL of ambient air.

    Then the sample goes through the gas detection tube and reacts with the chemical reagent. The size of the created stain is proportional to the concentration. The concentration can be instantly read using the scale printed on the tube without the help of a laboratory. The stopping point of a chemical reaction is easily read thanks to the lines printed on the tube.


  • what are the different measuring ranges

    Several measuring ranges are available for numerous gases and vapors (ppm, %, mg/m3, mg/L). This gives the opportunity to measure low and high concentrations with the same accuracy.


  • what are the most popular gas detection tubes?

    The most popular gas detector tubes are for hydrogen sulfide and carbon monoxide. There are 7 tube versions for hydrogen sulfide and 8 for carbon monoxide in the standard tubes classification. Their main difference is the measuring detection range.  All of our standard gas detector tubes are sold at the same price, whatever the measuring range.


  • does colorimetric and dosimeter tubes allow stel and twa readings?

    STEL – Short Term Exposure Limit

    STEL tubes measure gas concentration for hygiene at work and compliance with laws and regulations. These STEL tubes are the most common gas detection tubes (standard tubes).

    TWA – Time Weighted Average

    TWA tubes provide 8 hours samples. The instant reading of the stain size gives the monitored concentration for a day. TWA tubes speed up the laboratory treatment and allow people to quickly get correct exposure measurements. Thus safety matters are resolved faster.

  • are colorimetric tubes and dosi-tubes compliant with standards?

    Yes. The EN1231 European standard details the performance requirements and the test methods in laboratory conditions for gas detection tubes and their associated air sampling pump used for short term concentrations of specific chemical agents in ambient air.


  • what are the main benefits?

    . Gas detector tubes are more accurate for one-off measures

    . This system is cost effective

    . This method is intrinsically safe and can be used for any application, contrary to a gas detector


  • how much does it cost?

    In addition to the acquisition cost of an air sampling pump (less than 400 euros), only the tubes shall be purchased. They are low-cost and are delivered in boxes of 10 units for 59 euros. Make sure to choose a supplier with a unique price in order to facilitate the purchase. Contact GazDetect to know the latest prices and availabilities of gas detection tubes.


  • what are the applications of gas detection tubes?

    Gas detector tubes are used in many fields of activity for many detection operations such as:

    . Spills of hazardous materials interventions

    . Leakage cleaning

    . Wastewater treatment

    . Refineries

    . Leak detection

    . Marine and freight

    . Pharmaceutical industry

    . Fertilizers and chemical industry

    . Fumigation

    . Food industry

    . Power plants

    . Petrochemical industry


  • is it required to perform a leak test of the pump before use and how to do it?

    It is essential to always perform a leak test before each use of an air-sampling pump in order to be sure to get accurate measurements.

    For this purpose, be sure that the tightening nut is fully tightened. Once the pump handle is completely pushed (the lines on the pump shall not be seen), insert an unbroken tube into the pump entry. Align the mark (red line) onto the back and the handle marks (▲100). Pull the handle along the red line on the pump axis until the locking position then wait a minute. Unlock the handle turning it with a quarter turn and guide it gradually. Confirm that the pump is going back to its initial position and that the line on it cannot be seen.

    When the handle is unlocked, slowly and lightly hold it otherwise it could damage internal parts because of the pump vacuum.


  • what if i get a blurred result after a test?

    The discoloration of the reagent can sometimes be blurred on a gas detection tube. If so, take the average between the two ends of the blurred part.

  • is it possible to use gas detector tubes from an other brand than the pump’s?

    Even if it is possible, it is clearly not recommended.


  • how can i store and dispose gas detection tubes?

    It is recommended to store Gastec tubes in a cool (from 0 to 10°C) and dark place to preserve their quality. Any direct contact to sunlight could damage the reagent of the tubes. Always store them in a safe place and keep them away from children.

    As gas detection tubes are filled with sensitive reagents that can be corrosive, they need to be stored and handled safely and carefully.

    Used or expired gas detection tubes – break both ends of expired tubes – have to be submerged in water (no more than 20 tubes in 5 liters of water) during several hours (or all night long). The tubes can then be disposed with other glass garbage. The water can be poured into the sewers. As the quantity of reagents is minimal, there is no risk for people and the environment.

  • what if a gas detection tube breaks and i have reagent powder on the hands?

    Immediately wash your hands and avoid contact with the eyes and mouth.


  • can i use tubes even when they expired?

    No, using an expired gas detection tube can provide false readings. We strongly advise against using expired tubes.


  • what is the gastec tubes lifetime?

    Most of gas detector tubes have a lifetime of 1 to 3 years depending to the reagent and if stored in a cool and dark place. The expiration date is clearly marked on the gas detection tube packaging.


  • What is included in a gas detector tube system purchase?

    A Gastec pump system includes a carrying case, a Gastec pump, an instruction manual and replacement filters.

    Gastec detector tubes packs include an instruction sheet and numbered stickers. The packaging is printed with batch number, number of tubes included and expiration date.


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