INSIGHT INTO REAL-TIME ROOT CAUSES ASSESSMENT
Full-shift exposure sampling (typically using pumps and filter media, see picture at left) is the choice method in establishing compliance with OSHA regulations. Such samples produce a single 8-hour time-weighted average (TWA, see example results below) that is directly comparable to OSHA PELs and Action Levels, which are often full-shift limits.
TWA sampling is of much less use in engineering applications, where companies wish to implement controls that will be effective in reducing exposures. Process changes, elimination/substitution, ventilation, and worker practice modifications are all potentially costly endeavors, and it is highly recommended that companies proceed with care.
Advantages of Real-time Monitoring
An excellent example of the value in real-time monitoring is the differentiating source concentrations from fugitive concentrations. TWA sampling is weak in determining how much the background air impacts employee concentrations.
Source Concentrations – Often short duration, elevated concentration, related to employee activities
Fugitive Concentrations – Often extended duration, lower concentrations, independent of employee activities
The strategy of controlling these concentrations can differ significantly. Real-time monitoring excels at determining both background concentrations and source exposures from employee activities. Concentrations can often be composed of both source concentrations (typically high concentrations for short duration, related to the activities of the employee).
Real-time monitoring also offers a much more detailed view of how worker exposures change during the shift, identifying peaks and valleys that is invaluable in gaining knowledge on the activities which drive exposure.
Instead of one number, real-time monitoring methods can create thousands of measurements, all potentially linked to worker/facility activities through observations, activity logs, production data, and even video/audio recordings.
The collected data can be statistically evaluated in a number of ways to determine correlations that can be targeted for controls. Below are several examples of the root causes that are commonly observed in industrial environments.
A fairly common root cause of indoor air concentrations is the rising background. In this example (shown above), there are multiple factors (improper room air changeovers, insufficient supply, poor source capture) that is leading to a continually building concentration in the background air.
Another root cause is the result of a single large release the both obscures (masks) the actual concentrations, and greatly contributes to the personal exposure. Often these types of measured concentrations are the direct result of malfunctioning equipment, missing covers, or poorly-functioning ventilation. These can have a pronounced effect on full-shift averages, and often can be the source of great frustration, as results from shift-to-shift vary wildly depending on the prevalence of these unwanted indoor air changes.
The elevated background is another root cause, that is particularly difficult to contend with. Because workers will be exposed to elevated concentrations regardless of work activities, it is possible to cause entire departments to approach or exceed exposure limits. This type of root cause also masks information that would help identify other root causes. As such, it is recommended that these issues be remedied prior to detailed investigations. Typically this type of root cause is due to woefully insufficient ventilation (often because a system is inoperable or has been removed) or due to an complete lack of fresh air supply.
This root cause could either be source, fugitive, or both in nature. In this type of exposure, numerous repeated peaks or changes in air concentrations are noted. Often these can be directly correlated to either the monitored employee or a neighboring task utilizing either field observations or production data. This type of cause also identifies an area of inadequate control, as the elevated and repeated concentrations will negatively impact background air.
The repeated source is a common type of root cause, and often a difficult one to correct. This type of exposure, with short duration peaks and a quick return to background concentrations shows evidence of some control, but with contaminants likely passing through the breathing zone during capture. This type of root cause is often found in well-controlled, high energy processes such as welding, grinding, arc-air gouging, and spraying.
In addition to standard time-concentration real-time curves, additional statistical analysis can be performed on the data, as the data set (potentially numbering into the thousands of points) is often significantly large.
An Advanced Method to Determine Root Causes of Exposure to Respirable Crystalline Silica in Foundries, E. Pylkas, B. Scholz, American Foundry Society 118th Metalcasting Congress
Rooting Out Respirable Crystalline Silica. An Advanced Method Helps Metalcasters Determine the Causes of Exposure, E. Pylkas, B. Scholz, Modern Casting December 2014
Real-Time Monitoring for Silica Exposure Analysis, E. Pylkas, B. Scholz, Modern Casting January 2018
Insight IH Consulting has extensive knowledge in performing real-time monitoring. Eric Pylkas is a published (and award-winning, as our work received a Best Paper award from the American Foundry Society) author on the topic.
Call 262-347-6599 for assistance now.
20 February 2019
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