Passive TWA
Sampling occurs by natural diffusion. Position the tube with the appropriate holder; do not connect a pump.
GASTEC · TIME-WEIGHTED EXPOSURE
GASTEC Active and Passive TWA Gas Detector Tubes
Passive diffusion and active pumped sampling. Two methods, separate tube catalogues.
MEASUREMENT SYSTEM
Evaluate gas exposure over the sampling period.
TWA describes time-weighted average exposure over a defined period. GASTEC passive dositubes work by diffusion without a pump; active long-term tubes use a compatible automatic sampling pump. Select these systems separately from short-term measurements made with the GV-100 manual pump.
Request a Quote from NOVELActive TWA
Set the tube-specific flow and duration on a compatible GSP automatic pump. The GV-100 manual pump is not used for this method.
Choose by method
Target gas, duration and measurement objective determine the tube. There is no universal sampling time or flow rate.
TECHNICAL OVERVIEW
Technical Specifications
System, method and configuration
- Passive system
- GASTEC dositube + suitable holder; no pump
- Passive holder
- No. 710
- Active system
- Tube designed for automatic sampling + compatible GSP pump
- Current pump option
- GSP-501FT; verify tube instructions and pump operating mode together
- GSP-501FT flow mode
- Timer mode: 50–500 mL/min. Volume-mode settings of 10–49 mL/min operate intermittently at 50 mL/min.
- Sampling duration
- Tube- and method-specific; consult the instructions
- Result interpretation
- Use the tube scale, actual sampling duration and required corrections together
Tube-specific instructions determine the valid range, sampling procedure and corrections. Confirm the method for your application with NOVEL.
COMPLETE YOUR SYSTEM
Accessories and Consumables
710
Passive dositube holder
For positioning a pumpless dositube during personal sampling.
Request this accessory ↗
730
Personal sampling tube holder
For positioning the tube during active personal sampling; check compatibility with the selected tube.
Request this accessory ↗
GSP500FT-30
Belt-loop pump holder
Helps carry the GSP-501FT during personal exposure sampling.
Request this accessory ↗
GSP300-14
Protective cover for detector tubes
For protecting and securing the tube during active sampling.
Request this accessory ↗Request availability, pack quantity and compatibility by tube or accessory code. No live stock information is displayed.
GSP-501FT
Automatic Sampling for Active Tubes
Select the operating mode and sampling settings for the specific tube. Low volume-mode settings involve intermittent sampling; do not treat them as continuous flow.
NOVEL · VIDEO
GASTEC TWA Exposure Measurement
MEASUREMENT AND SELECTION
Frequently Asked Questions
Does a passive TWA tube need a pump?
No. A passive dositube works by diffusion. Do not substitute forced airflow; follow the positioning and exposure-time instructions for the tube.
Can I use an active TWA tube with the GV-100S?
The GV-100 manual pump is not used for this method. Select the compatible automatic pump, sampling mode, flow and duration specified for the tube.
Should every tube be sampled for eight hours?
No. Valid sampling duration, range and calculation vary by tube. Match the intended assessment period to the tube’s permitted sampling duration.
RELATED SYSTEMS
Other Measurement Options
Manufacturer technical sources: GASTEC TWA ↗ · GSP-501FT ↗
NOVEL