GAS4M Hydrogen Sulphide Gastec Detector Tubes 12.5 - 500ppm


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Excl. VAT: £28.50 Incl. VAT: £34.20
Excl. VAT: £28.50 Incl. VAT: £34.20

Product Description


GAS4M Hydrogen Sulphide (H2S) Standard Gastec Detector Tubes

Gas detector tubes are glass tubes that are filled with chemical reagent that absorbs and reacts with the target gas or vapour being measured.

A colorimetric stain (a colour change) is created. For most tubes, the concentration is read directly from the pinpoint accurate measurement scale on each tube.

This makes this form of monitoring ideal for spot sampling as it can be more accurate then electronic gas detectors.

The Gastec detector tube system is comprised of a handheld Gastec air sampling pump and Gastec detector tubes.


Measuring Range

12.5 to 25 ppm

25 to 250 ppm

250 to 500 ppm

Number of Pump Strokes




Correction Factor




Sampling Time

30 seconds per pump stroke

Detecting Limit

2.5 ppm (n=2)

Colour Change

White       Brown

Reaction Principle

Hydrogen Sulphide reacts with Lead Acetate to form Lead Sulphide, which colour is brown.

H2S + Pb(CH3COO)2                PbS + 2CH3COOH

Coefficient of Variation

5% (for 25 to 250 ppm)

Shelf Life

3 Years

Corrections for
temperature & humidity


Store the tubes at cool and dark place.


Possible coexisting substances and their interferences





Change colour by itself

Nitrogen Dioxide

1/4 time

Minus error

No discoloration

Sulphur Dioxide

1/1 time

Plus error

No discoloration



No effect

No discoloration

Calibration gas generation

Permeation tube method


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