Dear All,
Understanding the Difference Between STEL and TWA
What is the difference between STEL and TWA? And what is the application of the same in industrial safety?
Let me explain this by using a real-life example.
The present problem in Mumbai regarding commuting by road is traffic jams. Particularly at signal points, a lot of automobile emissions occur, leading to increased pollutants in the atmosphere.
If we consider this as a workplace and the work of automobile drivers and traffic police as working people, then STEL would be applicable to drivers. However, for police, the TWA would be applicable.
The drivers would pass through the polluted area in less time, but the traffic police would be there for all duty hours.
In most of the plating industries I have seen, the jobs are assembled on fixtures. Assembly is done at a workstation which has a U-type layout or in multiple rows adopting a single-piece flow concept. The assembly workstation is at the center or on one side of the shop. The chemical tanks have fume collection systems as well as scrubbers.
The operator has to go to the tanks for loading and unloading and then return to the assembly station for assembly/disassembly.
Workplace monitoring at the assembly station has to be done for TWA, where the operator works most of the time.
Workplace monitoring at the breathing height of the operator is to be done for STEL, as the operator goes to the tank only for loading and unloading, which takes less than 10 minutes.
The most ideal situation is to limit the concentration of pollutants to even less than TWA limits.
The Factories Act Second Schedule has defined different values for the above two.
I invite all of you to share your views on this matter.
Regards,
Sudhir