The health effects of exposure to VOCs depend on the concentration, the length of exposure, and the VOCs present because some VOCs are more toxic than others. Workplace exposure limits (WEL) therefore exist for each VOC with short-term exposure limits (STEL) typically applying to the maximum concentration over a 15-minute period, and time-weighted average levels (TWA) typically calculated over an 8-hour period.
Most countries set equal or similar WELs for each VOC, however, care should be taken to address any international differences. For example, in the USA and in most European countries, the 8-hour TWA limit for benzene is 1ppm, although lower levels have recently been proposed in Germany. Similarly, the American Conference of Governmental Industrial Hygienists has proposed a lowering of the benzene 15-minute STEL and TWA limits. Currently, the OSHA permissible exposure limit (PEL) is 1 ppm (8-hr TWA), and 5 ppm during any 15-minute work period. The NIOSH recommended airborne exposure limit (REL) is 0.1 ppm (10-hr TWA) and 1 ppm during any 15-minute work period.
Choosing the right VOC sensor technology
PIDs are the most in-demand and appropriate sensors for the measurement of VOCs for health and safety applications. This is because of their fast response (1-3 secs), and because they are the most selective technique to VOCs. In addition, with a choice of PID lamps it is possible to optimise the sensor for different applications, and known response factors enable quantitative analysis of specific VOCs.
For most PID sensor manufacturers, susceptibility to contamination and humidity is a major challenge, but these issues have been resolved within ION’s MiniPID sensor range. This is one of the main reasons behind ION’s position as the largest PID sensor manufacturer in the world. All MiniPID sensors have a patented design with a third electrode that nullifies potential humidity interference, delivering a stable signal from 0 – 99% RH.
Reliability is a critically important feature of sensors that lower health and safety risks. Uniquely, ION’s MiniPIDs incorporate an ASIC chip, which continuously monitors lamp and sensor performance, providing fail-safe assurance of sensor performance. The ASIC also manages the sensor to give exceptional temperature stability from -40 to +65o
C. Conclusion
The cost of designing ION’s world-class VOC sensors into OEM instruments, processes and systems is negligible in comparison with the potential costs and risks incurred by not specifying the best available technology.
Pioneering Gas Sensing Technology.
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