The concept of “decision fatigue” is a somewhat controversial one among those who study decision-making performance in various circumstances.  The notion that our decision-making capabilities are depleted through repeated use, akin to physical stamina, is anathema to many in the field.
            In order to competently study a phenomenon and its effects on human performance, it must be clearly defined.  A consensus definition of decision fatigue has been elusive, however, and remains a key point of contention in debates on the subject.  Disagreements about decision fatigue are as fundamental as whether or not the phenomenon is “real.”
            In this installment of the “Making Decisions” series, the definition of decision fatigue and the controversy it spurs are explored.  An alternative perspective is also offered, which sidesteps academic debate in favor of practical application of knowledge gained about what we call “decision fatigue” to improve individual and organizational outcomes.

            The Preference Ranking Organization METHods for Enrichment Evaluations (PROMETHEE) resemble previously-presented decision-making tools in some fundamental ways.  For example, it is a set of compensatory assessments employing pairwise comparisons.  However, substantial differences in PROMETHEE provide advantages not offered by other methods and, thus, warrant discussion.
            The use of various preference functions in PROMETHEE enable evaluations of criteria that more-accurately reflect the ways decision-makers think about their choices.  The determination of the “net desirability” of each alternative also differs from other compensatory methods discussed.  PROMETHEE methods are presented in this installment of the “Making Decisions” series, highlighting these key differences.

            ORESTE is a prioritization and decision-making tool that evaluates alternatives according to their deviations from a hypothetical ideal solution.  The acronym, translated from French, stands for “organization, storage, and synthesis of relational data.”  The method establishes a hierarchy of criteria that is then used to determine a hierarchy of alternatives.
            In this installment, a relatively-simple analysis is used to demonstrate the ORESTE method.  The hypothetical machine purchase of previous installments is revisited, maintaining continuity that facilitates comparison of methods.  A potential pitfall of the method and recovery options are also discussed.

            Decision-making tools vary in sophistication and in their applicability to some types of decisions.  The Fuller Triangle (FT) method is relatively simple; however, this comes with a tradeoff.  Similar to Analytic Hierarchy Process (AHP), presented in Vol. III (6May 2020) of this series, but less rigorous, FT may be less suitable to highly consequential or complex decisions.
            Multicriteria analysis (MCA) tools facilitate organization of decision information for several alternatives and attributes.  When the rigor of a complex method is not required and a decision is needed quickly, FT may be an excellent compromise.  In this installment of Making Decisions, the Fuller Triangle is presented, including some comparisons to AHP to facilitate selection of a decision-making aid.

            Assessments of a lighting system installation is necessary to determine its compatibility with shifting or evolving requirements.  A lighting system can be evaluated by direct measurement, calculation of theoretical values, or simulation of the space in software.  Each has its strengths and weaknesses; the choice of method to be employed depends on the status of the installation, objectives of the assessment, and available resources.
            This installment of the series provides an introduction to each type of assessment.  These methods are not mutually exclusive; the most useful evaluation may be obtained by blending methods.  The presentation of concepts is kept brief to maintain a manageable scope in the series.

            Cost is a critical component of any project to be predicted, monitored and controlled.  It is the one metric that everyone understands, at least on a superficial level.  Deeper understanding of project costs requires insight into the sources, benefits, and alternatives available.  Various tools are available to document and compare lighting system designs.
            Basic methods often lack accuracy, but are useful for preliminary screening purposes.  More-sophisticated methods capture greater detail, facilitating assessment of the impacts of design decisions and assumptions on project costs.  In this installment, common cost analysis methods are presented, from the simple to the complex.

            Light that does not contribute to its intended purpose, i.e. visual performance in a defined area, is wasted.  When it detracts from the experience of surrounding areas, light is obtrusive.  Wasted light is often obtrusive, but need not be to contribute to nuisance.  Systems that produce little wasted light also contribute to nuisance.  The existence of nuisance light is bothersome irrespective of its impact on visual performance, though it can be significant.
            Several aspects of nuisance light, also known as “light pollution,” are considered in this installment of the “Workplace Illumination” series.  Many parallels are evident between light pollution and “noise pollution.”  Review “Occupational Soundscapes – Part 15:  Community Noise” [15May2024] for a presentation of the latter; read on for a discussion of the former.

            Superficially, lighting for safety, security, and emergency situations may seem redundant.  While there is overlap among these lighting scenarios, they are differentiated by their primary purposes, operating conditions, and characteristic requirements.  There is also an interdependence among these lighting scenarios, despite independent operation in the majority of circumstances.
            In this installment of the “Workplace Illumination” series, the characteristics of safety, security, and emergency lighting are explored.  What separates them and what unites them in a cohesive lighting system design is discussed to enhance understanding of each lighting scenario and recognition of their interdependencies to support effective installation and maintenance.

            The importance of customizing lighting for individuals, tasks, and spaces has been conveyed in preceding installments of this series.  That theme continues here, where the unique characteristics of office spaces and their impact on lighting design decisions are explored.
            In most offices, the range of activities, or tasks, is relatively narrow, aiding specification of appropriate lighting parameters.  However, other factors, such as the type of displays in use, the proportion of time spent on each task type, visual capabilities of users, and psychological influences of lighting complicate system design.
            Competing task requirements and varying needs of occupants creates tradeoffs that must be considered.  Where balance cannot be achieved, priorities must be established.  Understanding the characteristics of office spaces and tasks is paramount if one hopes to design a lighting system that suitably balances its objectives.

            A local lighting strategy relies on area lighting (see Part 12) to provide minimum levels of illumination required to maintain safety and task lighting to provide the higher illuminances required for satisfactory performance of demanding visual tasks.  This strategy provides great flexibility in lighting small areas, allowing customization of the visual environment to suit the task and individual performing it.
            Customization of a task-specific area presents its own challenges, in part due to the proximity of luminaires to individuals performing the task.  Maintaining visual performance requires ensuring that sufficient light is provided where it is needed without sacrificing visual comfort.  Balancing these competing objectives requires another level of analysis and planning, which is the subject of this installment of the “Workplace Illumination” series.

            Daylighting is a form of general lighting used to create aesthetically pleasing spaces that maintain visual performance capabilities while reducing energy consumption.  Effective daylighting requires integration of electric lighting and appropriate control strategies to compensate for the variability of daylight and for use of the space during evening, nighttime, or early-morning hours.
            Daylighting provides several advantages; however, the design of daylit spaces is fraught with challenges.  A number of tradeoffs among design parameters must be considered, including room size and orientation, window size and placement, energy consumption, psychological effects, and more.  This installment of the “Workplace Illumination” series explores design tradeoffs and the evaluation of a space’s potential for effective daylighting.

            Area lighting is used to ensure safe navigation throughout a space and to perform simple tasks.  For these purposes, relatively low illuminances are sufficient; visually-demanding tasks require higher illuminances and may also require stricter control of light distribution, color characteristics, or other parameters.
            Area lighting often refers to the illumination of a large, open space, such as a factory or warehouse.  This may also be called general lighting, as it is “all-purpose” illumination; it is not customized for a specific task or area within the larger space.  Here, “general” is also used to denote the relevance of much of the information presented to application-specific lighting systems.  Specialized applications, such as office spaces, and adaptations required are discussed further in future installments of the series.

            Thus far, the “Workplace Illumination” series has presented primarily conceptual information (i.e. physics) and the human side (i.e. physiology) of lighting and vision.  This installment begins an exploration of the hardware (i.e. physical structures) used to bring designed lighting to fruition.  Luminaires are fundamental building blocks of lighting systems and embody a substantial portion of their design specifications.
            Despite their central role, many users of lighting systems fail to appreciate the extent to which the specification of luminaires influences the comfort, safety, and productivity of workspaces.  The functions of a luminaire, how its components serve those functions, and various types of luminaires are presented in this installment.  A basic understanding of luminaire functions is required to optimize lighting system design or even to create functional lighting.

     All five human senses are used to collect information about our surroundings.  However, far more information is collected and processed by visual means than by any of the other senses.  Visual information is given higher priority than other sensory stimuli by both the structure and function of the brain.  Thus, visual communication is the dominant form of information transfer and a critical consideration in lighting system design.
     The use of color is an important element of visual communication.  As discussed in previous installments of this series, color and illumination choices are interrelated; some combinations are better enablers of effective communication than others.  This installment explores some forms of visual communication and impacts of color and lighting system design choices.

     Like all human capabilities, visual performance is influenced by a number of factors.  Inborn imperfections in the eyes, physical injury, infection, and other ailments can affect visual capabilities.  Changes in visual capabilities are also experienced due to advancing age.  The variety of potential afflictions results in a wide range of severity and compensability.
     Focusing an image on the retina, differentiating colors, and distinguishing between objects or details are functions of the visual system that can be effected by various maladies.  Changes can also occur in the non-visual system, affecting circadian timing and related functions.  These changes may be more difficult to correlate with perceived effects, as links to non-visual system functions are typically less obvious than that of, say, a blurred image to visual system functions.
     An introduction to several light-related maladies, including innate and acquired conditions, is provided in this installment.  Effects on workplace visual performance, potential treatments, and countervailing techniques are presented in brief.  The prevalence and severity of these conditions among the workforce are parameters that must be considered in an analysis of lighting system design requirements.

     All human visual capabilities are, ultimately, matters of perception.  Of course, the specific nature of each input to the visual system – the visual stimuli – is important; however, similar stimuli can result in significantly different visual perceptions.  It is the interpretation of visual stimuli, occurring in the brain, that defines our visual perceptions.
     In addition to wavelength, luminance, and related measures of illumination, the brain uses other information to interpret visual inputs.  Proximity of objects to one another, color variation, brightness, contextual clues, cultural norms, and other factors can influence the perception of, and reaction to, a visual scene.
     This installment explores some of the factors that influence visual perception.  Some factors defy measurement; some are relegated to the subconscious through training, experience, or other influence on an individual’s attentional budget.  Those of which observers are aware may still defy explanation of their impact, for many are unfamiliar with the mechanisms involved.  Nonetheless, all are important contributors to interpretations of our surroundings.

     It is easy to underestimate the importance of color as a distinct component of human visual capability.  Color often plays a significant role in our recognition of objects and perceptions of spaces.
     The perception of color varies among individuals.  Defined systems of identification make it possible to compare colors and to describe them in a way that can be communicated effectively.  Coherent communication of color information is the key to color specifications (e.g. product design) and color matching (e.g. paint mixing).
     This installment of the series explores the production, “measurement,” communication, and human perception of color in our environment.  Concepts introduced in previous installments are also revisited and expanded in the context of color vision.

     Several aspects of vision contribute to a subjective assessment of clarity or visibility of an object.  Though many characteristics of vision are quantifiable, ultimately, subjective assessments often dominate discussions of lighting needs.  The challenge for lighting designers and industrial hygienists is to combine subjective feedback and objective data to extrapolate lighting system requirements.
     In Part 5, objective measures of light were introduced; the discussion involved the source of light (e.g. luminance) and its path (e.g. refraction, reflection).  In this installment, the receiver of light, the human visual system, is once again considered.  Factors contributing to visual capabilities and quantifiable measures are explored.

     Photometric measurements quantify the light incident on a workspace, but more information is needed.  Effective lighting system design requires that qualitative parameters also be considered.  A strict technical definition of photometry limits the term’s applicability to measurements of the intensity of light.  Here, use of the term is expanded to refer to more-comprehensive evaluations of lighting.  That is, for purposes of this series, photometry includes both quantitative and qualitative assessments.
     Understanding the terms and quantities associated with photometry is critical to the assessment of the suitability of a lighting system.  It also supports the ability to predict or compare the relative performance of two or more lighting systems.  Providing information needed to develop assessment skills is the primary objective of this installment.  A brief introduction to measurement equipment is also provided.

     The functions of the eye presented in Part 3 often get the most attention.  This is simply because they are closely associated with the most-salient features of our sensory perceptions.  That is to say that the eye’s role as a component of the visual system is most familiar; the previously discussed functions may even be mistakenly conceived as the entirety of the visual system.  The exploration in this installment demonstrates that this is far from the reality.
     In addition, the eye plays an important role in the non-image-forming system; the term non-visual system is used here for brevity and to maintain an obvious contrast between functional attributes.  The non-visual system affects sleep/wake cycles, alertness, and related circadian rhythms.

     The human eye is a complex organ that functions in ways many do not realize.  It uses sophisticated adaptation mechanisms to operate in various “modes” as dictated by environmental conditions.  Coordinated use of two eyes simultaneously provides additional “modes” of functionality.
     The structure of the human eye is explored in this installment of the “Workplace Illumination” series.  Basic functions of the eye, derived directly from its physical structure, are also discussed.  Increasingly complex functions and adaptations are explored further in subsequent installments, building on this foundation of knowledge.

     To maintain a safe, productive workplace, one must understand the physical environment and how humans interact with it.  Providing proper illumination to workspaces requires knowledge of the basic concepts of light transmission and vision.  These topics are undertaken early in the “Workplace Illumination” series to provide this foundation.
     Extensive research has garnered great insight into these topics, such that much of it is beyond the scope of this series.  The presentation in the series provides an introduction to the information available at a depth appropriate for practical application.  It also serves as a refresher for those revisiting the subject matter.

     Light, like heat, noise, and vibration, can seem innocuous at first.  However, the characteristics of light in a workplace, its consistency, and its delivery can profoundly affect the health, safety, and productivity of workers.  Thus, workplace illumination warrants further investigation and, yes, its own series in “The Third Degree.”
     Many similarities exist between the human experiences of light and sound.  It likely comes as no surprise, then, that presentation of fundamental information in this series parallels that in the “Occupational Soundscapes” series.  Links between the two also exist, for example, when used in conjunction to increase the effectiveness of communication.
     These similarities and combined uses are explored, along with physiological and psychological impacts of lighting design choices and related topics.  This introductory installment provides a glossary of terms and, like those before it, a directory of published installments for convenient access to all series content.

     The Safe + Sound program is a joint initiative of several safety-oriented organizations to promote development of and broad participation in workplace safety and health programs.  In August each year, this year-round campaign boosts its outreach and recognition efforts by hosting a week-long event.
     Running from August 12 – 18, Safe + Sound Week 2024 highlights job hazard analysis, providing reference material and guidance to facilitate successful execution.  Nearly 4000 businesses, industry groups, educational institutions, and governmental bodies have registered for participation.  In addition to in-house efforts, some organizations also open events to the public.

     The Occupational Safety and Health Administration (OSHA) has submitted its proposed occupational heat standard to the Office of the Federal Register (OFR) where it is pending official publication.  OSHA has made a draft version publicly available for review; it includes background information and justifications in addition to explanations of the requirements it creates.
     At nearly 1300 pages of “regulese” (a dialect of legalese), OSHA’s Notice of Proposed Rulemaking (NPRM) is a substantial document.  Though it only becomes official when published in the Federal Register, a document of this magnitude, in terms of both physical size and potential consequences, warrants a preview.  Any modifications that occur during OFR review are likely to be more aesthetic than substantive, ensuring the effort is not in vain.  To ease the burden of reviewing the massive NPRM, this installment of the “Thermal Work Environments” series provides an overview and summary of important points.