Easy operation:
Step 1: Record Start Time
Step 2: Break tube end
Step 3: Place in tube holder
Step 4: When measurement is finished, write down finishing time
Step 5: Find the TWA using the formula; TWA (ppm) = Dositube reading (ppm=hr) / Actual sampling time (hr)
| Gas or Vapour to be Measured | Measuring Range (ppm) | Gastec Tube No. |
|---|---|---|
| Acetaldehyde | 0.1-20 | 91D |
| Acetaldehyde | 4-1,200 | 151D |
| Acetaldehyde | 1.2-360 | 152D |
| Acetic Acid | 0.5-100 | 81D |
| Acetic Anhydride | 0.45-90 | 81D |
| Acetone | 5-1500 | 151D |
| Acetone | 1.4-420 | 152D |
| Ammonia | 2.5-1,000 | 3D |
| Ammonia (Low) | 0.1-10 | 3DL |
| Benzene | 2.4-600 | 122DL |
| 1,3-Butadiene | 1.3-200 | 174D |
| Carbon Dioxide | 0.02-12% | 2D |
| Carbon Monoxide | 1.04-2,000 | 1D |
| Carbon Monoxide (Low) | 0.4-400 | 1DL |
| Chlorine | 0.08-100 | 8D |
| Chlorine | 2.4-240 | 132D |
| Cumene | 3.4-850 | 122DL |
| trans-1,2-Dichloroethylene | 3.9-600 | 174D |
| trans-1,2-Dichloroethylene | 6-600 | 132D |
| Dimethylamine | 1.9-750 | 3D |
| N,N-Dimethylethylamine | 4-1,600 | 3D |
| Ethanol | 100-25,000 | 112D |
| Ethyl Benzene | 2.8-700 | 122DL |
| Ethylene | 1.56-240 | 174D |
| Ethylene dichloride | 3.9-600 | 174D |
| Formaldehyde | 0.1-20 | 91D |
| Formic Acid | 0.55-110 | 81D |
| Furfural | 0.3-60 | 91D |
| Hydrazine | 1.6-650 | 3D |
| Hydrogen Chloride | 1-100 | 14D |
| Hydrogen Chloride | 1.8-180 | 132D |
| Hydrogen Cyanide | 1-200 | 12D |
| Hydrogen Fluoride | 1-100 | 17D |
| Hydrogen Fluoride | 2.5-250 | 14D |
| Hydrogen Peroxide | 0.5-40 | 32D |
| Hydrogen Sulphide | 0.2-200 | 4D |
| Isoprene | 2.6-400 | 174D |
| Methylamine | 0.19-19 | 3DL |
| Methyl Ethyl Ketone (MEK) | 2-600 | 152D |
| Methyl Ethyl Ketone (MEK) | 0.125-25 | 91D |
| Methyl Ethyl Ketone (MEK) | 6.5-1,950 | 151D |
| Methyl Isobutyl Ketone | 11.5-3,450 | 151D |
| Methyl Isobutyl Ketone | 4-1,200 | 152D |
| Ntric Acid | 0.8-80 | 14D |
| Nitric Acid | 0.32-32 | 17D |
| Nitrogen Dioxide | 0.1-30 | 9D |
| Nitrogen Dioxide (Low) | 0.01-3.0 | 9DL |
| Styrene | 26-6,500 | 122DL |
| Sulphur Dioxide | 10-600 | 5DH |
| Sulphur Dioxide | 0.2-100 | 5D |
| Tetrachloroethylene | 3-150 | 133D |
| Tetrachloroethylene | 1.5-150 | 132D |
| Toluene | 2-500 | 122DL |
| Trichloroethylene | 3-300 | 132D |
| Triethylamine | 5.3-2,100 | 3D |
| Trimethylamine | 0.23-23 | 3DL |
| Vinyl Chloride | 1.56-240 | 174D |
| Xylene | 3.4-850 | 122DL |
Gastec Passive Dosi-Tubes are used to measure time weighted average (TWA) gas concentrations over several hours. The Dositubes do not require the use of a sampling pump as ambient air diffuses through the tube.
Each tube is filled with a diffuser and chemical reagent in parallel that allows the gas to disperse at a constant flow. This provides longer discolouration and better demarcation. The tubes are normally attached to the worker’s collar or clothing in the breathing zone with the holder and collar clip.
- Uses gas diffusion method
- Tube holder clips onto workers collar for breathing zone measurements or can be used as an area monitor
- Measures time weighted averages (TWA) for numerous gases (See Dositubes List)
- Direct measurement can be made from the calibration lines printed on each tube