Industrial / Gas Detection
Instruction Manual for Gastec Benzene Detector Tube No. 121SP
Quick guide for the Gastec Benzene Detector Tube No. 121SP. Includes technical specifications, measuring ranges, pump stroke requirements, reaction principles, and interference handling information.
Table of contents
Important Information
This document provides technical specifications and usage guidelines for the Gastec No. 121SP Benzene Detector Tube. These tubes are designed for the detection of benzene and must be connected as a pair (pretreatment tube and detector tube) before use. Ensure the pretreatment reagent is not fully consumed during sampling to maintain accuracy.
Performance Specifications
- Measuring range: 0.2 to 20 ppm (requires 3 pump strokes) or 20 to 66 ppm (requires 1 pump stroke).
- Sampling time: 6 minutes for 3 pump strokes; 2 minutes for 1 pump stroke.
- Detecting limit: 0.1 ppm (with 3 pump strokes).
- Color change: White to Brown.
- Corrections for temperature & humidity: Unnecessary.
- Relative standard deviation: 10% (for 0.2 to 5 ppm), 5% (for 5 to 20 ppm).
- Shelf life: 2 years.
Interference and Coexisting Substances
Aromatic hydrocarbons other than benzene are trapped in the white layer of the pretreatment tube. Note that if the pretreatment reagent is entirely consumed (the whole white layer turns brown), a higher reading will be given.
Coexisting Substances
- Hexane (<= 500 ppm): No interference.
- Toluene (<= 300 ppm): No interference.
- Xylene (<= 350 ppm): No interference.
Reaction Principle
The detection process involves the following chemical reactions:
Pretreatment tube: Interference gas removing.
Detector tube: 2C6H6 + HCHO -> C6H5CH2C6H5 + H2O; C6H5CH2C6H5 + H2S2O7 -> Condensation polymer.
Calibration
Calibration is performed using the diffusion tube method.
Manufacturer information
Gastec Corporation
Practical help
Common problems
Pretreatment reagent consumed
If the whole white layer in the pretreatment tube turns brown, the reagent is exhausted, which will result in a higher reading.
Interference from other hydrocarbons
Aromatic hydrocarbons other than benzene are trapped in the pretreatment layer; ensure the pretreatment tube is connected correctly.
Before use
- Ensure the pretreatment tube and detector tube are connected before use.
- Verify the number of pump strokes required for the target concentration range (3 strokes for 0.2-20 ppm, 1 stroke for 20-66 ppm).
- Check that the pretreatment layer is white before starting.
Specs in practice
- Measuring range
- 0.2 to 20 ppm (3 pump strokes) or 20 to 66 ppm (1 pump stroke).
- Sampling time
- 6 minutes for 3 strokes, 2 minutes for 1 stroke.
- Detecting limit
- 0.1 ppm with 3 pump strokes.
Model compatibility
- Hexane (<= 500 ppm), Toluene (<= 300 ppm), and Xylene (<= 350 ppm) do not cause interference.
Manual page author
Michael Turner
Technical manual editor
Reviews PDF manuals for structure, safety notes, and practical product details so readers can find the right information quickly.