Gastec 4HM Hydrogen Sulphide Detector Tube

 4HM Tube is a gas detector which performing measurements using a gas sampling pump

Feature

• On-site measurements can be performed easily by anybody, anytime and anywhere, in a short time
• Easy-to-check direct reading possible due to the calibrated scale directly printed on the tube
• An extensive measuring range can be obtained by adjusting the sampling volume
• In order to assure high precision, each production lot is tested and calibrated independently, Each detector tube has its own quality control number printed on the tube
• Long shelf-life with excellent long-term stability

Performance

Measuring range	25 to 50 ppm	50 to 800 ppm	800 to 1600 ppm
Number of pump strokes	2（200 ml）	1（100 ml）	1/2（50 ml）
Correction factor	1/2	1	2
Sampling time	1.5 min	45 sec	30 sec

Detecting limit : 5 ppm (2 pump strokes)
Colour change : White → Brown
Corrections for temperature & humidity: Unnecessary
Relative standard deviation: 5 %(for 50 to 800 ppm)
Shelf life : 3 years

Reaction principle

H₂S ＋ Pb(CH₃COO)₂ → PbS ＋ 2CH₃COOH

Possible coexisting substances and their interferences

Substance	Concentration	Interference	Changes colour by itself to
Nitrogen dioxide Sulphur dioxide Ammonia Carbon dioxide Carbon monoxide Mercaptans Organic gases & vapours	≧ 1/4 ≧ 1/1	－ ＋ No No No No No	No No No No No No No

Calibration gas generation

Permeation tube method