Graphical Presentation of Measured Parameters in a Video
One of rhe most important goals for designers of industrial ventilation is to reduce the concentration of an air contaminant in the breathing zone of the workers. Smoke, dust lamps, and graphical presentations of area measurements are very important tools for the studies of airflow in the workplace and how the contaminant is dispersed out of the workplace. Those methods will, however, only give good indications of how much of the contaminant reaches the breathing zone. Strategies to visualize the concentration at the breathing zone may therefore serve as an important tool for the industrial ventilation expert.
One method for the visualization of workers’ exposure to air contaminants is the PIMEX method.1,14 The method is based on the simultaneous use of real-time monitoring instruments for the contaminant in question and video recording. The instrument is placed so that it samples in the breathing zone of the worker. The work is videotaped with the help of a video camera. The results from the measurements are presented as a graph, which is superimposed on the video picture. Many different technical solutions for this have been presented. Equipment that is available on the market uses telemetry to transfer the signal from the instrument to a laptop computer equipped with needed hardware and software for the task. The software makes it possible to present data as a bar graph or as a time-concentration graph, in both cases continuously updated. The software also facilitates a detailed analysis regarding the variation of concentrations in the breathing zone and their dependence on the situation in che workplace.15,16 Figure 12.9 shows two examples of how data is presented in the video picture.
Tary contaminant, exposure To the right, a moving graph and digits showing the same
This method has been used for a variety of applications to visualize the concentration of different air contaminants in the breathing zone and how it relates to factors like design of local ventilation, etc. Typical situations where it has been used are when the contaminant source is close to or handled by the worker, e. g., welding, painting, and woodworking.
The most important advantage with this visualization method is that it highlights the object of design effort, the concentration in the breathing zone of the exposed worker. There are many reasons to do so. One is that the presence and motions of the worker near the source or the ventilation units will have a considerable influence on the flow field around him or her and thus on the dispersion of the contaminant from the source to the breathing zone. If the designer of the ventilation system does not take this into consideration, there could be a big risk of failure in many situations. Another reason is that good communication between the expert, the industrial ventilation designer, and the subject of the work will facilitate solutions that not only function in technical terms, but also are accepted and in the best case also understood by the worker. A method that visualizes the concentration of the contaminant in the breathing zone is then an important pedagogic tool.
A disadvantage of this method, as with some of the methods described above, is that it presumes access to relatively complicated equipment that also implies basic training of the user.
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