Industrial / Gas Detection
User Manual for Gastec 136L Methyl Bromide Detector Tube
Quick guide for the Gastec 136L Methyl Bromide Detector Tube. Includes measurement procedures, technical specifications, correction factors, and safety instructions for accurate gas detection.
Table of contents
Quick Guide for Gastec 136L Detector Tube
The Gastec 136L detector tube is designed for the detection of Methyl Bromide in air or industrial areas. For safe and accurate operation, always use Gastec detector tubes exclusively with Gastec Gas Sampling Pumps. Do not interchange parts with non-Gastec components, as this may cause inaccurate readings, void warranties, or lead to serious injury.
Specifications and Measuring Ranges
The measuring range depends on the number of pump strokes performed:
- 2.5 - 10 ppm: 4 pump strokes (Correction factor 1/4, 1.5 minutes per stroke)
- 10 - 100 ppm: 1 pump stroke (Correction factor 1, 1.5 minutes per stroke)
- 100 - 200 ppm: 1/2 pump stroke (Correction factor 2, 45 seconds)
Operating Conditions: The tube operates within a temperature range of 0 - 40°C (32 - 104°F) and a relative humidity range of 0 - 90%. No correction is required for temperature or humidity within these ranges.
Measurement Procedure
- Perform a leak check on the pump before inserting the tube.
- Break the tips off a fresh primary tube and analyser tube using the pump's tip breaker.
- Connect the marked ends of the tubes with the provided rubber tubing.
- Insert the analyser tube into the pump inlet, ensuring the arrow on the tube points toward the pump.
- Ensure the pump handle is fully pushed in and align the guide marks on the pump body.
- Pull the handle out until it locks at one pump stroke (100 mL). Wait 1.5 minutes to confirm sampling completion.
- For concentrations below 10 ppm, repeat the sampling procedure three more times. For concentrations above 100 ppm, use a fresh tube and perform a half pump stroke.
- Read the concentration level at the interface where the stained reagent meets the unstained reagent.
- If necessary, multiply the reading by the correction factors for pump strokes and atmospheric pressure.
Correction for Pressure
To correct for atmospheric pressure, use the following formula: Tube Reading (ppm) x 1013 (hPa) / Atmospheric Pressure (hPa).
Interferences
The following substances may cause interference and produce a yellow color change, potentially leading to false positive results:
- Chlorine
- Bromine
- NOx
- Saturated Halogenated Hydrocarbons
Safety and Disposal
The reagent in both the primary and analyser tubes contains a small amount of hexavalent chromium. When disposing of used or unused tubes, follow all local government rules and regulations regarding hazardous waste.
Manufacturer information
Gastec Corporation
Practical help
Common problems
False positive readings
Check for interfering gases such as Chlorine, Bromine, NOx, or Saturated Halogenated Hydrocarbons, which can cause a yellow color change.
Inaccurate results
Ensure you are using a genuine Gastec pump and that the tube is inserted with the arrow pointing toward the pump.
Disposal of used tubes
Tubes contain hexavalent chromium; dispose of them according to local environmental regulations.
Before use
- Verify the tube is within its shelf life (check the box label).
- Perform a pump leak check before inserting the tube.
- Ensure the pump handle is fully pushed in before starting.
- Align the guide marks on the pump body.
- Ensure the arrow on the tube points toward the pump inlet.
Specs in practice
- Measuring Range
- 2.5 to 200 ppm, adjusted by the number of pump strokes (4, 1, or 1/2).
- Sampling Time
- 1.5 minutes per full stroke or 45 seconds for a half stroke.
- Reaction Principle
- Chemical reaction with o-Tolidine resulting in a color change from white to yellow.
Model compatibility
- Use only with Gastec Gas Sampling Pumps.
- Do not use non-Gastec parts or components.
Manual page author
Emily Carter
User documentation editor
Prepares concise manual descriptions and highlights the most useful setup, operation, and maintenance information for readers.