Control of Workplace Hazards for the 21st CenturySetting the Research Agenda
White Paper: Engineering Control Technology Research
The purpose of these brief summaries or "white papers" is to outline topics
for discussion of new or enhanced research on control technology and personal protective
equipment. Specifically, the summaries are intended to initiate, not limit, dialog at
specific sessions of the conference "Control of Workplace Hazards for the 21st
Century: Setting the Research Agenda" to be held March 10 12, 1998, in Chicago
The opinions and conclusions expressed are not considered as final statements of NIOSH
policy or of any other organization.
The objective of engineering control technology is to provide pragmatic recommendations
on the prevention and control of worker exposure to hazardous conditions. The purpose of
this paper is to discuss the future direction of research on this topic. First, this paper
reviews the current status of engineering control technology and states a vision for the
future application of engineering control technology. Then, the knowledge gaps and
research needs in the following topics are discussed:
- Control Strategy
- Prevention of exposures.
- Control of exposures.
Current Status of Control Technology Research
Frequently, engineering control technology is frequently focused on the application of
local exhaust and dilution ventilation to reduce worker exposure. For example, in NIOSH's
Engineering Control Technology Branch, nine of ten present research projects are focused
upon ventilation as a control measure. One project is looking at fundamental exposure
causes, in this case material dustiness. This narrow focus is also typical of research
papers published by the industrial hygiene community. In reviewing papers for the American
Industrial Hygiene Association's Best Engineering Paper Award for 1997, the committee only
had nine papers to review, seven of these papers were focused upon ventilation. Only one
paper was focused upon an overall control strategy.
A Vision of Control Technology
While ventilation is an important component of a comprehensive control plan, a more
holistic strategy involving the prevention, minimization and control of exposures can be
used to provide optimum control. The ideal time to prevent or minimize the hazards is
during the initial construction or perhaps during the renovation of a process. In the
industrial hygiene community, the term "substitution" generally refers to the
selection of a material with a lower toxicity to replace a material with higher toxicity.
Exposure prevention can also be accomplished by selecting materials, the material's form,
processes, process equipment, and process configuration to prevent or minimize worker
exposure. In dealing with control technology from a holistic perspective, one makes
process decisions to minimize the contaminant generation and worker exposure before
addressing the control measures. Furthermore, process choices can be made to enhance the
ability of control measures such as local exhaust ventilation to control worker air
contaminant exposures. This generally involves the enclosure of emission sources and the
use of ventilation and air cleaners to capture or contain contaminants.
Control Technology Strategies
Analysis of Research Gaps
In using engineering control technology to control workplace hazards, some private
companies use a comprehensive strategy to protect their workers . In addition, some need
to devise control strategies for the safe use of their products (product stewardship). To
develop control strategies, information is needed on the ability of different control
approaches to protect workers.
Generally, engineering control technology field research addresses the need to look at
different strategies. During applied field studies of control measures, exposure
measurements are made at different operations or plants along with ventilation system
measurements and observations. Types of information collected during such studies include:
air flow patterns, contaminant, temperature, humidity, production rates, generation rates,
and quantitative identification of exposure sources. This information and professional
judgement can be integrated to develop conclusions and recommendations about the control
measures studied. Generally, these studies provide useful insights and control options.
Although field studies do provide useful insights, one can only use professional
judgement to apply empirical findings from one situation to another situation. In
reviewing new processes before construction, one needs to estimate the magnitude of the
resulting exposures. Thus, there is a need to develop an approach to predicting exposure
from a process flow sheet, the manner in which ventilation is applied, and a knowledge of
the material's properties. There is a need for the occupational safety and health
community to work with engineering and manufacturing community to design equipment so that
health and safety concerns are addressed.
Field studies frequently do not consider the applied economics of controlling the
hazard. In the business world, economics is an important consideration in the selection of
process options. Simply stated: Economics determines what actually is done. Concerns about
trade secret information and confidential business information limit the dissemination
about economic impact of control measures. This is especially true when one is considering
actual process options. Certainly, field studies can document factors which drive costs.
Possible Research Topics
These research projects could enhance the development of control technology strategies:
- Quantitative models relating exposure to process parameters which will assist in control
decisions. Research in this area will help evaluate the reliability, and economics of
control decisions and provide guidance on the information necessary for collection in
field studies of exposure.
- Economics and control strategies.
Exposure Prevention and Minimization
Hazard prevention research has received very minimal attention in the industrial
hygiene community. However, this area of research offers great potential for reducing
worker exposures. Successful research will probably require a more fundamental
understanding of the processes involved. For example in order to develop a relevant test
to characterize a powder's ability to generate dust or liquid's tendency to create mist, a
fundamental understanding of the forces causing aerosol generation and particle adhesion
are needed. Presently, there is very little research being published on these topics and
purely empirical efforts have not yielded completely satisfactory results.
Possible research areas
- Fundamentals of dust generation by solids. The physical form of solid (granules, flakes,
slurries, powder, etc) can greatly affect aerosol generation. If one knew more about the
generation of aerosols by powders, it might be possible to devise more appropriate
dedusting treatments and to devise more relevant tests of material dustiness.
- Fundamentals of aerosol generation by mists. In the machining industries, additives to
suppress mist generation provide only a factor of two reduction in mist exposures.
Perhaps, if one understood the details of mist generation, it would be possible to devise
additives which are more successful at suppressing mist generation.
- Performance of seals and fittings on process equipment. The ability of process equipment
to minimize leakage is an important means of controlling emissions from process equipment.
- Application of Process Safety Management review techniques to the control of worker
exposures. In reviewing the design of equipment to prevent catastrophic losses, elaborate
review processes have been devised. Perhaps, the same sort of review can be devised for
contaminant generation so that designers are encouraged to think about process choices
which affect generation rates and occupational exposures.
Generally, occupational safety and health researchers have conducted much research on
the application of local exhaust and dilution ventilation to control worker exposure.
Recommendations on the application of ventilation are a product of practically every
project conducted by the NIOSH Engineering Control Technology Branch. High velocity low
volume (HVLV) ventilation has been studied and is a technique which controls the exposure.
The successful application of local exhaust ventilation is complicated. In order to
address these complications, Computation fluid dynamics (CFD) needs to be incorporated
into applied ventilation related research. Also, the identification of wakes and eddies in
actual operations can be difficult.
In recent years, recirculation has been used to conserve energy in the workplace
including offices and machining operations. Air cleaners are used in cabin filtration on
vehicles such as tractors, airplanes, and forklift trucks. Air cleaners are frequently
discharged back into the workplace because of energy considerations and environmental
rules. Thus, there is a need to study the industrial hygiene implications of air cleaner
performance and reliability. Anecdotal reports indicate that some facilities use
recirculation because the EPA permitting process is too burdensome.
Potential Areas of Research
- Application of computational fluid dynamics to the design of local exhaust ventilation
systems. This could be used as a part of an effort to develop mathematical model of
workplaces. The models are needed to predict the effect of workplace changes upon
- The use of microprocessor-based process controllers that, in principle, could
incorporate sensors and basic decision-making for the operation of ventilation systems and
- Recirculation. Evaluate the safety and health implications of air cleaner performance.
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