MALODORS

The olfactory senses signal the presence of some harmful airborne stimuli, but sometimes they fail to do so, and there are frequent “false alarms.” As mentioned in Chapter IV, people have historically avoided bad-smelling air for fear that it signaled illness-causing conditions. In the nineteenth century, the criteria for ventilation commonly arose from the notion that odorous air contained harmful ingredients known variously as crowd poison, morbific matter, and anthropotoxin.¹⁸ For instance, Russell stated in The Atmosphere in Relation to Human Life and Health:⁵²

Organic matter is given off from the lungs and skin, of which neither the exact amount nor the composition has been hitherto ascertained. Their quantity is very small, but of its importance there can be no doubt…. Since this organic matter has been proved to be highly poisonous, even apart from carbon dioxide and vapor, we may safely infer that much of the mischief resulting from the inspiration of rebreathed air is due to the special poisons exhaled by the body.

In the absence of instrumentation to detect the presence of small amounts of odorous organic vapors, the nose remains a sensitive indicator. Surprisingly, even today there are no good rules for laymen or scientists to relate perceived odor quality to toxicity. Some odorous signals are used to warn about toxic hazards (e.g., mercaptans are used in natural gas to signal leaks). We may know from experience that some foul-smelling living spaces pose no overt danger, but people will still avoid such places. We may argue that this avoidance is derived from mere discomfort, but occupants may fail to see the situation in such benign terms.

In the early twentieth century, the New York State Commission on Ventilation performed a set of experiments regarding the effects of occupancy odor on human comfort and performance.⁴⁶ In a popular synopsis of this 8-yr effort, Winslow⁷⁰ stated:

We may summarize our discussion of the physiology of ventilation as follows: The chemical vitiation of the air of an occupied room (unless poisons or dusts from industrial processes or defective heating appliances are involved) is of relatively slight importance. The organic substances present, manifest as body odors, may exert a depressing effect upon inclination to work and upon appetite; therefore, occupied rooms should be free from body odors which are obvious to anyone entering from without. (Such odors are never perceived by those who have been continuously in the room while they have been accumulating.) Objectionable effects of this sort have only been demonstrated, however, with a carbon dioxide content of over .2 per cent, which would correspond to an air change of less than 6 cubic feet per person per minute.

During the 1930s, Winslow and Herrington⁷¹ demonstrated that “dust odor” similar to that from a heating system could also depress appetite.

Winslow implied that the olfactory sense generally adapts to prevailing odorous stimulation in such a way as to reduce discomfort. Similarly, Cain reported that a temporary reduction in olfactory sensitivity, perhaps in conjunction with affective habituation, presumably explains why workers in some malodorous industries eventually find the odorous atmosphere unobjectionable.¹⁷ In contrast, people who live near malodorous sources of pollution seem to experience adverse olfactory reactions of constant or even increasing severity. For example, residents exposed frequently to malodorous emission of factories complained of chronic headaches, nausea, coughing, disturbance of sleep, and loss of appetite.⁶⁸ Those adverse reactions seem to arise as a consequence of industrial odors that are more or less unremitting and are beyond the residents' control. But when the source is in the occupied space, some control (or avoidance) may well be possible. (Tobacco smoke, traditionally the most bothersome odorant, is a common exception.)

Complaints about irritation of the eyes, throat, and nose are common and increasing among people in newly constructed or newly renovated offices.⁴ These complaints may arise from a confluence of low, energy-conserving rates of ventilation and emission of odorous or irritating substances, such as formaldehyde, from new furnishings. Tobacco smoke may exacerbate the problem. The course of the reaction of the common chemical sense of those exposed may vary considerably.¹⁶ One person may notice irritation immediately; another may notice it only after occupying a space for a few hours, but continue to experience it long after leaving the space and possibly fail to associate the irritation with its source. As a further complication, it has long been suspected that formaldehyde acts as an olfactory anesthetic.⁵⁸

NOISE

Discomfort due to noise has received more attention than that related to any other type of sensory stimulation. Noise-induced discomfort occurs in a great variety of situations, ranging from disturbance of sleep to difficulty in hearing in the workplace. Noise standards and regulations abound: for outdoor noises, for sound insulation in buildings, for controlling the risk of occupation-related deafness, and for guarding against hearing difficulty and annoyance in offices, schools, and hospitals. The context can have a strong bearing on the degree of annoyance. Nemecek and Grandjean⁴⁵ surveyed a large office and found that most of the employees were disturbed by noise that was considered well within professional design standards. The “noise” came from conversations, and it was content, rather than intensity, that was the disturbing attribute.

Experiments in both human beings and animals have shown that stressful effects from nondeafening noise arise without respect to the “meaning” of the auditory stimulation.⁶² Physical attributes that seem particularly relevant to annoyance include intensity, concentration of energy within high frequencies, temporal and spectral complexity, duration, and the suddenness of sounds.³⁴ Table VIII-1 shows results of a survey made to determine the importance of various physical and perceived attributes of annoying sounds.²³ The respondents judged loudness the most important attribute, with suddenness next in line. The next three most important attributes comprised cognitive features (sound is man-made, sound cannot be turned off, sound is unnecessary). The preeminence of loudness in the determination of annoyance has led to recommendations, such as those in Table VIII-2, for tolerable maximal loudness in various types of rooms.³⁴ The loudness values listed here refer to continuous noise in the period between 7 a.m. and 10 p.m.

TABLE VIII-1

Contributions of Various Characteristics of Sound to Annoyance.

TABLE VIII-2

Suggested Maximal Tolerable Intensities in Various Indoor Locations for More or Less Continuous Noise between 7 a.m. and 10 p.m.

Both human and animal laboratory experiments have shown hormonal effects of noxious, although nondeafening, noise exposure. Even exposures of about 70 dB can increase the output of adrenal corticosteroids.^{6 26} Sound intensity this low can also cause constriction of peripheral blood vessels.³⁸ Such changes, and other physiologic manifestations, usually fail to outlast the stimulus, but do cause concern that noise might eventually lead to more chronic symptoms of stress or affect sleep. Frequent interruption of sleep or alteration in the normal progression of sleep patterns may be thought to jeopardize physical or mental health eventually. Fortunately, adaptive alterations in the pattern of sleep seem to minimize most short-term consequences of disruption by noise.³²

In addition to physiologic manifestations, noise exposure produces adverse behavioral manifestations. Experimental exposure to noise diminished the quality of interpersonal contact,¹⁵ increased aggressiveness,²⁷ and impaired willingness to help persons in need.⁴¹ Loud noise, particularly intermittent noise, may alter productivity. The effect may be facilitative, rather than inhibitory; that has led to the speculation that noise may interact with other environmental factors and with personal factors to achieve a degree of arousal desirable for work.²⁹

TEMPERATURE

There is little scientific information on the connection between thermal conditions and productivity.⁴² In laboratory experiments at 65–85°F (18–29°C), productivity often reached a peak at nonpreferred temperatures.⁷³ In an apparel factory, productivity (i.e., piecework) varied little, if at all, with thermal conditions (note, however, that workers were paid by the piece).⁴⁸ When given the opportunity to express an opinion, people will be consistent in their preference regarding environmental conditions. The “comfort vote” has literal meaning in research on thermal acceptability. It refers to a subjective rating on a seven-point scale of comfort, on which the midpoint signifies thermal neutrality. A large body of research has made it possible to determine, by means of “comfort equations,” the combinations of several factors—notably air temperature, humidity, radiant temperature, air velocity, degree of activity, and type of clothing—that will minimize discomfort. The range of acceptable combinations of environmental conditions is known as the “comfort zone.”

Figure VIII-1 depicts summer and winter comfort zones adopted in 1981 by The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).^{2 10} The comfort zones show the relationship of comfort to temperature and humidity during “light” activity. At least 80% of occupants should feel comfortable—no more than slightly warm or slightly cool—in these zones. The comfort zone is different between summer and winter, because people wear more clothing during the winter. The thermal resistance of a clothing ensemble can be measured precisely in “clo” units. Table VIII-3 offers an example of how a change in clothing will be reflected quantitatively in clo values and optimal operative temperatures. Operative temperature is determined on the basis of air temperature and average radiant temperature. In an interior zone with only a slight radiant component, the operative temperature approximately equals dry-bulb temperature.

FIGURE VIII-1

Acceptable ranges of operative temperature and humidity for persons wearing typical summer clothing and typical winter clothing. These “comfort zones” assume that occupants are engaged in only light activity. Reprinted with permission (more...)

TABLE VIII-3

Temperatures for Thermal Acceptability (Comfort) of Sedentary or Slightly Active Persons (≤1.2 mets) at 50% Relative Humidity.

Insulation from clothing and degree of activity interact in determining acceptable temperature. The ASHRAE standard therefore offers an equation to convert acceptable operative temperature (°C) for sedentary occupancy (1.2 mets) to that for more active occupancy (e.g., housework at 2 mets, garage work at 3 mets): t_o (active)= t_o (sedentary)−3 (1+clo) (met−1.1), where t_o represents operative temperature. In addition to steady-state features of the thermal environment, the standard considers temporal nonuniformities (e.g., temperature cycling) and spatial nonuniformities (e.g., vertical temperature differences). Some limited nonuniformities, such as monotonic temperature drifts, may prove both economical and acceptable.¹¹

Conditions for thermal comfort seem to vary little, if at all, with such factors as geographic location, sex, body build, ethnic background, and even age.²⁴ The effects of aging seem to merit some special consideration. Basal metabolic rate decreases progressively with age, but, according to Fanger,²⁴ evaporative heat loss does, also. The two changes seem to offset each other, although the elderly spend much more time than the young in sedentary activities. Furthermore, with the lower temperatures now common indoors during winter, the elderly seem to have a narrower temperature range over which they can increase their thermal resistance.⁵³ Because of sensory adaptation, a sedentary old person may fail to notice the symptoms of impending hypothermia until it becomes severe. Adequate clothing is the best precaution against cold distress. In the United States, people were not energy-conscous until rather recently, and both young and elderly seem to need more education regarding the way to match clothing to the thermal load of the environment.

INTERRELATIONSHIPS OF ENVIRONMENTAL FACTORS

Other prominent factors in the indoor environment include lighting, furnishings, and the size and configuration of the space. Control of type and quality of illumination is often an aspect of design. Professional and aesthetic preferences can govern the choice of intensity, placement of sources, hue, and degree of contrast of lighting. These matters often receive much attention in the workplace. The question of whether light, temperature, and sound are optimal should be viewed in terms of such needs as productivity and accident prevention. In the home, the considerations are different from those of the workplace—questions of efficiency and productivity place few constraints on the physical environment at home, and few persons obtain professional advice regarding ways to maximize comfort and minimize hazards in the home.

Proshansky and colleagues⁵⁰ stated that “behavior in relation to a physical setting is dynamically organized: a change in any component of the setting has varying degress of effects on all other components in that setting, thereby changing the characteristic behavior pattern of the setting as a whole.” That conclusion may seem obvious; however, the need to consider it arises in experiments where a source of discomfort is expected to decrease productivity, but increases it instead. Such studies may often fail to give precise answers regarding the importance of one or another environmental factor, but they can help to heighten our awareness. Awareness is a powerful tool in recognizing and dealing with the complex interplay of safety, health, comfort, and productivity indoors.

SUMMARY

A person's perception of discomfort can provide a useful indicator of possible adverse effects of environmental agents. Discomfort gives immediate incentive to avoid or to correct environmental deficiencies. There is little information regarding whether long-term exposure to sources of discomfort will eventually cause adverse health effects. This question has no global answer. The discomfort caused by a thermally variable environment may lead to physiologically useful acclimatization and to behavioral strategies that diminish the impact of environmental challenges. In contrast, exposure to moderately intense noise—e.g., 80 dB(A)—leads to no such physiologic accommodation in the auditory system and may eventually cause hearing loss in susceptible persons. As an added complication, low-intensity sound may cause considerable discomfort and even intense autonomic reactions in persons sensitized to the “meaning” of the sound. The long-term deleterious effects of continuous activation of the autonomic nervous system are not known, and efforts to measure such symptoms as nausea, headaches, and dizziness and learn their clinical significance should be encouraged.

Some airborne chemical contaminants cause discomfort via stimulation of the olfactory sense or the common chemical sense. This probably serves a useful purpose, inasmuch as people will often avoid bad-smelling atmospheres, regardless of any known toxic properties. The discomfort can also lead to closer investigation of the source of malodors.

A generic relationship between discomfort and productivity has eluded specification. It seems possible at best to state only that the point of maximal productivity may not coincide with the point of minimal discomfort, but will hardly fall at the point of maximal discomfort. Comfort is derived from the harmonious interactions of many things, including physical factors, context, motivation, social factors, attitudes, and skill at the task at hand. Therefore, it is related to all aspects of a person's behavior and may prove just as difficult to predict. Nevertheless, appropriate attention to the maintenance of proper lighting, air, and thermal conditions increases the diversity of activities and the numbers of people that can be accommodated in comfort.

RECOMMENDATIONS

• Subtle forms of discomfort often arise from the use of manufactured products, building materials, and consumer products. Therefore, identification of the products leading to irritation and of its duration can be used by manufacturers in the design of safer products.
• The relationships of subjective complaints of discomfort to associated symptoms—such as headaches, nausea, and other health effects—should be studied in persons of different ages and in different categories of other kinds, such as socioeconomic status. Objective data from these studies could be useful in targeting the design characteristics of buildings.
• For each type of discomfort (e.g., noise-induced discomfort and odor-induced discomfort), there is a need for research on how to relate stimulation to discomfort.

DEFINITION OF “PRODUCTIVITY”

There is national recognition that our resources are not infinite, and this recognition has led to reexamination of the earlier definitions of “productivity.” The demands for increasing productivity have had a serious impact on the physical and mental well-being of both the workforce and the consumers of its production, to say nothing of the impact on “quality of life” in our society. Thus, the measure of productivity was expanded to consider the “efficiency of the output.” Productivity is currently addressed in terms of cost effectiveness— “Does it work?”—with considerations of timeliness, effects obtained or results achieved, and such humanistic elements as manner of performance and methods of achieving the results. The periods of redefinition of “productivity,” at the national level, can be dated by Presidencies. The simple concept that productivity equaled output was displaced, during the Franklin D.Roosevelt era, by consideration of cost per unit of production. This idea was displaced, during and after the Kennedy administration, by consideration of the effectiveness of policies to improve productivity. Over roughly the last 50 yr, the definition of “productivity” has used a complex of interacting entities and characteristics, including quantity and quality of product, monetary cost, timeliness, and human costs. Human costs include those engendered by the manner of performance, the method of achieving the results, and the actual benefits, as compared with the social costs. As long as people are involved in the definition, productivity can be adversely affected by pollution (defined as the presence of any unwanted or unnecessary element in the environment).

PRODUCTIVITY IN INDUSTRIAL ENVIRONMENTS

Pollution will affect productivity at two distinct levels; its physical effects on the means of production, or on the product itself, which are directly related to the quality of the product; and the effects on the health of the worker. Air contaminants can be categorized into particulate and gaseous, organic and inorganic, visible and invisible, submicroscopic and microscopic, or toxic and harmless.

With even “clean,” country air containing particles bigger than 0.3 µm at over 10⁶/ft³ and atmospheric dust loads of 20–200 tons/mi² per month in cities, the physical effects of pollution can be substantial. Solid particulate contaminants accumulate on surfaces, contaminate food products, and discolor walls, ceilings, floors, and furnishings; nonparticulate contaminants (vapors and gases) also affect food products, discolor surfaces and furnishings, and cause deterioration of fabrics and finishes. When one considers that unnecessary cleaning, repairs, and painting and untimely replacement are nonproductive, one can see that the physical effects of pollution are a drain on productivity. The loss of light to dirt on windows, the role of dirty car windows in causing accidents, the inefficiencies of dirty cooling coils or heating elements, the erosion of building structures, and the diversion of resources (both money and time) because of these problems all contribute to a lowering of productivity. Indeed, tobacco smoke and cooking and body odors form the primary requirement for ventilation in nonindustrial occupied spaces. About 17% of the national energy use is devoted to moving, heating, or cooling air for ventilation; such pollutants can be considered a major factor in limiting the energy available for productivity.

Even though many contaminant effects are related to specific products or processes, their effects on the health of workers are not, and they can be dealt with generically. As opposed to the physical classification of contaminants mentioned above, a spectrum of health effects of pollutants can be suggested: lethal-disabling-sickening-irritating-annoying-distracting-discomforting.

Although the lethal end of this spectrum has captured more attention (e.g., consider lead poisoning and asbestos exposure), in the present social climate, where productivity depends more on what people will produce than on what they can produce, the greatest effects on productivity will probably be incurred toward the discomfort end of the spectrum. Obviously, premature death or chronic disability removes the individual producer. But even a slight increase in illness or malaise can reduce productivity by absenteeism or by “taking it easy” for a few days. Indeed, even momentary distraction, discomfort, annoyance, or physical irritation will reduce the quantity or quality of production.

In a 1979 NIOSH pilot study in industrial plants in Oregon and Washington, workers were examined for occupational diseases and other conditions. Hearing loss (noise pollution?) was the most frequent (28%), and skin conditions were next (18%), followed by lower respiratory conditions (14%), toxic and low-grade toxic effects (14%), upper respiratory conditions (11%), and eye conditions (9%).⁶¹ No such data exist for nonindustrial environments, but, if one considers today's nonindustrial and social environments (discos, lounges, rock concerts, radios, and record-players and their sound intensities), it seems probable that decrements in hearing due to “noise pollution” represent one of the leading correlates of productivity losses. Although the incidences of the other health effects mentioned above may differ in a nonindustrial setting, they are all likely to occur.

The impact on productivity from pollutants that are simply annoying, distracting, or discomforting (temperature, odor, and soiling) has been largely ignored until recently. However, insight into their anticipated effects can be gained by examination of the tables of “relaxation allowances” established to develop production standards for jobs or of “environmental differential-pay plans” developed to provide extra compensation for putting up with a variety of undesirable conditions. Allowances of formal rest breaks and pay differentials, based primarily on physical strain, began to be common around 1950. These allowances have expanded; they were based increasingly on psychologic factors in the 1960s and on environmental factors in the 1970s. Some rest allowance seems appropriate to lessen the abuse of the worker, but growing public concern over environmental factors may have led to increases in rest allowances and pay differentials. These provide documentation of the costs of the adverse effects of environmental pollution better than anything else available.

The relaxation allowances consider four elements. A standard 10% time break, 18 min every 3 h, is considered adequate for personal needs, such as a trip to the rest room or a coffee break, although in practice it tends to be more generous in most industrial settings. A second set of relaxation allowances are based on such physiologic factors as energy demands, postures, body motions, and restrictive protective clothing; a third is based on psychologic factors associated with timing, monotony, and the required concentration (diligence). A fourth deals with environmental factors, such as thermal quality, humidity, other air pollution, noise, dirt, and vibration. Williams⁶⁵ suggested that relaxation allowances (i.e., percent of productive time lost) be determined as a function of environmental conditions, as follows:

1.

Thermal and atmospheric conditions: Consider whether, despite or in the absence of protective clothing or equipment, and extractors or air-conditioning equipment, the air conditions in terms of temperature and purity are such that additional demands are made when performing the work; air conditions are defined as:

A.

Adequate ventilation and circulation with normal climatic humidity.

B.

Inadequate ventilation and circulation with non-standard climatic conditions causing some discomfort.

C.

Very poor ventilation and circulation. Fumes, dust, steam, causing irritation to eyes, skin, nose, throat.

2.

Physical conditions, including noise. Consider the general physical conditions of the environment in relation to the work being performed and the degree of discomfort caused by dirt, oil, grease or water and other liquids, ice, chemicals, etc. Consider also whether noise is irritating by irregularity, or uncomfortable pitch or volume.

In an effort to check the allowances, some 16 establishments and 145 different jobs, including about 6% female workers, were examined. In general, the findings supported the relaxation-allowance approach. The allowances for these environmental factors are obviously only suggestions. Therefore, it is doubtful whether additional research would provide any reliable refinement of the productivity losses due to environmental factors, because such psychologic factors as motivation, leadership, expectation, and need (and their interactions) are as important as the environmental factors in determining productivity.

In the environmental pay-differential approach. Federal Personnel Manual letter 532–17 established specific pay differentials for exposure after November, 1970, to “various degrees of hazards, physical hardships and working conditions of an unusual nature,” as follows:

Dirty Work: Performing work which subjects the employee 4% to soil of body or clothing: a) beyond that normally expected in performing the duties of the classification; and b) where not adequately alleviated by mechanical equipment or protective devices …; or c) when their use results in an unusual degree of discomfort.

Cold or Hot Work: At or below 32°F or above 110°F 4% Working with or near:

Although these pay differentials are not directly relatable to productivity decrements, the increases in direct costs of protection are explicit, and productivity decrements are therefore also explicit; hence productivity losses can be inferred. However, the basis for such pay differentials is at least as much political as factual; additional research along these lines is not likely to be very informative.

Determining productivity losses caused by pollution is extremely complex. Even with careful definitions and measurement, it appears unlikely that any simple cause-effect correlations can be established that would not be destroyed by alterations in motivation, leadership, expectation, and need.

PRODUCTIVITY IN NONINDUSTRIAL ENVIRONMENTS

These very limited considerations of interaction between air quality and productivity can be defined in terms of units of production, percentage of rejects, or costs per unit of salable product. Models have been developed to show the influence of heat exposure on productivity,⁸ but, as with the comfort models, there has not been much work on validating them. Thus, the models provide only a theoretical prediction of reductions in work capacity. Few studies have been carried out on the causes of productivity decreases in industry, and even fewer in institutional settings. The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) has supported studies of the potential benefits of air-conditioning in schools.⁴⁹ Air-conditioned classrooms and libraries were heavily preferred (by about 95%), but it could be inferred that air-conditioned schools attract better teachers and that better teachers get better results. Similarly ambiguous results have attended most of the numerous ASHRAE studies on air-conditioning criteria.¹ The difficulties rest in part with the variability of actual environmental conditions, as distinct from those supposedly maintained by the control systems, and in part with the difficulty (suggested by Wyon⁷⁴ ) of defining the criteria for such environmental qualities as “comfort” and air quality, as distinct from the criteria for performance.

There has been growing recognition of the difficulties in demonstrating linkages between environmental quality and productivity, and the pace of research in this subject appears to have slackened in the last few years. Concerns about productivity have been focused more and more on workplace layout and worker motivation; that is probably appropriate, because they have direct and tangible impacts on productivity. The most tangible effects of air quality on productivity and quality of life are the adverse effects on health and longevity; even so, experimental confounding easily blurs any direct linkages. E.g., when the U.S. Army introduced its “MUST” field hospital, which used air-conditioning, in Vietnam, patient survival and hospitalization time were clearly improved, but argument arose as to whether the improvements were caused by air-conditioning or by staffing.

PARTICLE DEPOSITION

Deposition of dust particles on walls and other surfaces is the most common cause of soiling. The number and surface and mass relationships of particles are important in soiling. A 5-µm-diameter spherical particle has 1,000 times the mass of a 0.5-µm particle of the same material, but only 100 times the surface area. Thus, it is the submicrometer particles that have greater soiling potential, although the relationship between particle size, optical characteristics, and soiling is complex. However, larger particles contribute more to abrasion, and lint can foul equipment. Mechanical heating, cooling, and ventilating systems commonly include air filters to remove lint and larger particles. In some manufacturing operations, such as production of microelectronic circuits,⁷ it is essential to have very-high-efficiency filtration for removal of submicrometer particles. The average home or place of business does not approach these high standards of air cleanliness, although an increasing number of residences are using electronic air-cleaners capable of removing submicrometer particles.

Larger particles settle faster than smaller ones. Gravity sedimentation is an important mode of deposition, but it may be comparatively unimportant in deposition of very small airborne particles. Figure VIII-2 is a plot of Stokes diameter of a particle as a function of time required to settle 1 m in air. Settling times are plotted for particles with densities of 1 and 2 g/cm³. Water and oil droplets have densities of about 1 g/cm³. Figure VIII-2 is a somewhat idealized representation, but it permits a visual estimate of the relative sedimentation rates of large and small particles. Particles larger than 5 µm in Stokes diameter settle in a comparatively short time; particles smaller than 1 µm may remain suspended for hours, unless they become attached to other particles, walls, or surfaces. Davies has reviewed deposition from moving aerosols.²²

FIGURE VIII-2

Particle diameter (d) and density (ρ_p) as a function of time required to settle 1 m in air, according to Stokes's law.

Electrostatic and thermal precipitation are two important mechanisms by which particles are deposited. Penney and Ziesse⁴⁷ have measured the mobilities of airborne dust particles under the influence of thermal and electrostatic gradients and have estimated an average effective thermal mobility of 2.4×10⁻⁸ m²/°C·s and an effective electric mobility of about 11×10⁻⁸ m²/V·s. These values can vary widely for different dust particles, but they are useful approximations for the design of dust-collecting equipment. Penney and Ziesse also noted that an electrostatic precipitator that does not capture all particles causes more soiling than an air-cleaner of the same efficiency that does not charge particles. Apparently, the particles become electrically charged, and that causes them to attach to surfaces more readily. Thus, it is important that the precipitator be designed for maximal capture.

The force of attraction between two molecules (London-Van der Waals force) varies as the inverse of the 7th power of the distance between them³⁹ and plays a role in interparticle adhesion or adhesion to surfaces. The electrostatic attraction of particles to surfaces is very strong at distances of a few angstroms, but diminishes rapidly with increasing distance. From the standpoint of soiling, London-Van der Waals forces are probably important in particle retention after a particle contacts a surface. Corn¹⁹ calculated the electrostatic attraction between a charged particle 1 µm in diameter and an adhering particle or surface in which it induces an equal and opposite charge. Assuming a particle charge of 15 electrostatic units (e.s.u.)—i.e., 15×10⁻⁹ coulombs—and a separation of 1 nm (10 ), he estimated a force of 5.2×10⁻³ dynes, which is about 10⁷ times the gravitational force, assuming a density of 1 g/cm³. However, this is only one one-thousandth of the estimated Van der Waals force.

Capillary attraction is a mechanism of particle retention due to adsorbed liquid films. Capillary attraction is probably more important in fouling (where air comes into contact with damp coils or pipes) or in particle filtration (where adhesive liquids are applied to the filter) than in most everyday soiling of walls and surfaces. When the radius of the liquid film at the point of contact is small, compared with the radius of the particle, the force of attraction between a sphere and a plane surface, with a film of liquid interposed, may be expressed by the relationship F=4πγr, where F is the capillary force, γ is the surface tension of the liquid, and r is the particle radius.²⁵ Corn¹⁹ has suggested that that equation is approached only at relative humidities near 100%, where water is in the liquid phase. At lower vapor pressures, the force is less.

The surface-to-volume relationship of particles increases dramatically as particles become very small, and this relationship is important in soiling. Surface forces have a much greater role in determining soiling properties of small particles than of larger particles. Very fine particles cling to a glass slide when the slide is inverted. Walker and Fish⁶⁴ demonstrated that removing small particles by either liquids, airstreams, brushing, or gravity was more difficult than removing large particles.

Human activities can cause agitation that resuspends deposited particles. Primarily, it is the larger particles that are more readily redispersed by this means. Hunt,³¹ in experiments using a light-scattering-particle counter, showed that vacuum-cleaning a rug or operating an electric fan caused a severalfold increase in the number of particles larger than 3 µm, but only a slight perturbation in the number of smaller particles. But other activities—such as smoking, heating, or cooking—produced primarily submicrometer particles. Also, aerosols in this size range are probably produced by condensation from the vapor phase, rather than by dispersing preexisting particles from surfaces or from a powder.

MOISTURE AND FUNGAL GROWTH

Fungal growth is another cause of soiling and deterioration that generally occurs in areas with high humidity and low ventilation. Microbial slimes in air-cooling and -humidifying units, plumbing fixtures, condensation trays, and drains cause serious and often costly mechanical problems. These and other airborne organisms can discolor paint, weaken fabrics, and degrade foodstuffs. Microorganisms can also lead to odors, such as the musty smell of a damp basement. Schaffer⁵⁵ has reviewed many of the effects of moisture in buildings, including the promotion of fungal growth. Moisture can be generated internally from combustion during heating and cooking, drying clothes, bathing, and even breathing, and it can come from the outside during periods of high humidity. Moisture generated indoors can result in high humidities when there is no dehumidification, when ventilation rates are low, or when a structure has tight vapor barriers in walls and partitions. Fungal growth in ducts or on walls and surfaces has been observed after the use of large amounts of outside air for ventilation during damp periods.

Water vapor is not ordinarily regarded as a pollutant. Not only is it essential to support the growth of microorganisms, but, if it is present in excessive amounts, it can cause more visible effects, such as peeling of paint and wallpaper. It also has an effect on comfort (as discussed earlier), and it can enhance the effect of other pollutants. Hermance et al.,³⁰ for example, have noted this in studying damage to telephone contacts by airborne nitrates.

GASEOUS POLLUTANTS

The important gaseous pollutants—such as ozone, sulfur dioxide, oxides of nitrogen, and carbon monoxide—affect the corrosion and deterioration of materials. Ozone can cause cracking of rubber and some other elastomers. The amount or rate of cracking of stretched rubber bands has been used as a method for determining low concentrations of ozone.^{14 63} Not only does ozone occur in the outdoor air, but trace amounts can be produced indoors by arcing of electric motors in tools and appliances and by corona discharges of electrostatic air-cleaners. Sulfur dioxide and oxides of nitrogen may also contribute to corrosion and deterioration, but they are more often considered as potential health hazards. Carbon monoxide is comparatively inert and does not react on surfaces; although it is a hazard to health and safety, it does not normally cause soiling or deterioration.

EFFECTS OF TIGHT CONSTRUCTION

Reduction of infiltration resulting from tighter construction decreases the amounts of pollutants coming from outside, but can cause increases in the concentrations of those generated indoors, unless there is a change in ventilation rate. To achieve the full benefit of tight construction without increasing soiling, corrosion, and deterioration, provision must be made to abate or eliminate indoor-generated moisture and the indoor pollutants at their source. Particles and moisture are probably the most important agents that affect the rates of soiling, corrosion, and deterioration. Particle counts are usually lower indoors,⁹ but not always. Cooking, cleaning, and other indoor activities intermittently distribute particles, as well as moisture. Sources of many other pollutants are discussed in Chapter IV.

As mentioned earlier, increased tightness of buildings can result in increased moisture indoors. Previously, moisture generated indoors has leaked out through the building structure, but, as these paths of elimination are reduced, it may be necessary to use dehumidifiers.

EFFECTS ON MAINTENANCE FOR CORROSION AND DETERIORATION

Andrews⁵ estimated that the cost of corrosion in the United States exceeds $25 billion per year. This expense is reported to be due to additional fuel, maintenance, or replacement costs. Although the fraction of these costs caused by indoor pollution was not reported, it can be assumed that even a small percentage could represent a great financial impact over the lifetime of a building. Four types of corrosion, which must be controlled in building environmental control systems, are shown in Table VIII-4, with some methods of prevention.

TABLE VIII-4

Types of Corrosion and Methods of Environmental Control in Buildings.

If the quality of the indoor air is degraded, the increased concentration of contaminants can aggravate scaling of heat-exchanger surfaces.⁵ For example, the air in a space with relatively high moisture content often is recirculated across a cooling coil for dehumidification. Increased carbon dioxide and sulfur dioxide of the indoor air may react with the condensed water and accelerate corrosion on the cooling coil.

Reports of increased maintenance of heat-exchangers or rotating equipment necessitated by degradation of indoor air quality were not found in the literature, but the appropriate conditions for increased corrosion have been reported.^{5 19 25 31 47 55} For example, Hermance et al.³⁰ reported that telephone switching equipment required increased maintenance because of nitrates.

Inasmuch as nitrogen oxides and sulfur oxides can be present in indoor environments, either from indoor sources or from outdoors, the potential exists for corrosion of electric components in most indoor environments.

EFFECTS ON HOUSEKEEPING

Cleaning and care of materials and properties in institutional spaces represent approximately 15–20% of the total annual operating costs of these facilities (W.W.Whitman, personal communication). In turn, annual operating costs can be approximately 50–75% of the annualized initial investment of buildings.^⋆ Thus, any degradation of the indoor air quality that causes an increase in housekeeping can seriously affect the life-cycle cost of a building.

As buildings have become more energy-efficient, the moisture content has been generally reported to have increased, owing to decreased infiltration.⁵⁵ Additionally, the concentrations of smoke particles and other contaminants from smoking and other indoor activities have increased (see Chapter IV). Thus, the rates of soiling and deterioration of exposed surfaces may be accelerated, as a result of degradation of indoor air quality.

Windows are a primary site for accelerated soiling, especially during the heating season. Because resistance to heat transfer through windows is usually one-tenth to one-third that of adjacent walls, the inside surface temperatures of the windows will be much lower than those of the walls. If the inside surface temperatures of the windows are lower than the dewpoint temperature of the occupied space, condensation will occur at these surfaces. Particles and gaseous contaminants in equilibrium with the water vapor will be deposited on the window surfaces with the condensate. As the condensate leaves the windows by evaporation or draining, the other contaminants will be left on the surfaces as residue, thus increasing the required frequency of cleaning. Boyce¹³ reported that, when windows are not thoroughly cleaned periodically, a cloudy film builds up that can be removed only with muriatic acid. To combat pollution in Los Angeles, Boyce stated, aluminum mullions and transoms on the CNA park Plaza Building must be cleaned annually with mild steel wool and oil must then be applied to protect the metal. If outdoor pollutants are transported indoors, or if similar pollutants are generated indoors, the interior surfaces of windows might require similar treatment.

Indoor lighting efficiency is also affected by indoor air quality. Williams⁶⁶ reported that dirt accumulations on lamps and fixtures can reduce light output by 10–50% over the rated “end-of-life” of the lamps. Thus, as dirt and film accumulate on fixtures and lamps, cleaning and relamping frequencies must be increased to maintain proper illumination.

Another major category of housekeeping expense is related to the care of floors and carpeting. Darling²¹ reported that, on a national average, 40–60% of the working hours of cleaning crews is required for floors and carpeting and that carpeting soils more quickly in industrial centers than in suburban areas, where air pollution is less severe.

Furniture, paintings, sculptures, and musical instruments are also affected by indoor air quality. The special requirements for environmental control in museums, art galleries, and auditoriums are indicative of the care that is required to protect these properties.³

METHOD OF TREATMENT

There are ways to reduce the indoor pollution that causes soiling and deterioration. For example, air filtration reduces the amount of airborne dust. Most central heating and air-conditioning systems contain air filters. Although these are usually not of high efficiency, they do reduce dust. An electronic air-cleaner designed for a specific system can remove still more particles.

The visible effects of undesirable thermal precipitation of dust on walls near grilles and radiators may be reduced by shields that direct air away from walls.

Dehumidifiers remove excessive moisture. However, during the heating season, humidity is often low indoors, and it may be necessary to add moisture to the air, to prevent stress cracking in furniture and other wood products due to excessive drying. (The relationship between human comfort and humidity and temperature is discussed earlier in this chapter and in Chapter IV.) Tobacco-smoking places an added burden on air-cleaning and ventilation systems. In public buildings, smoking is often prohibited or restricted to specified areas.

Particles and other airborne materials generated in cooking may be largely removed by exhaust systems near the point of generation.

Activated carbon and other adsorbent air-cleaners are sometimes used in buildings in high-pollution areas to remove gaseous pollutants. However, these are not in general use, and they present some special problems. For example, it is harder to determine when an adsorbent filter needs to be changed than a particulate filter (see also Chapter IX).

RECOMMENDATIONS

Some of the commonly recognized agents that produce soiling and deterioration have been discussed in the foregoing paragraphs, but additional questions need investigation. With regard to removal of indoor particles, where is the point of diminishing returns in improving the efficiency of particulate filters? Likewise, where is the point of diminishing returns reached in increasing the rate at which air is removed from an occupied space and filtered? Dust composition may also be important. There have been a few analyses of indoor dust,^{28 43} but much less work that has tried to relate soiling, corrosion, or other deleterious effects to dust composition and particle size. Thus, the effectiveness of dust removal technology and the specific nature of the dust, as they relate to soiling and deterioration, need further investigation.

Information on the role of gaseous pollutants in soiling or corrosion is lacking.

REFERENCES

1.

American Society of Heating, Refrigerating and Air-Conditioning Engineers. Symposium Bulletin. Air Conditioning Criteria for Man's Living Environment, Louisville, Kentucky, June 24–28, 1973. New York: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1973. 33 pp.

2.

American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASHRAE Draft Standard 55–74R. Thermal Environmental Conditions for Human Occupancy. New York: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., April 1980.

3.

American Society of Heating, Refrigerating and Air-Conditioning Engineers. Commercial and public buildings, pp. 3 .1–3.16. In ASHRAE Handbook and Product Directory. 1978 Applications. New York: American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc., 1978.

4.

Andersen, I. Formaldehyde in the indoor environment—Health implications and the setting of standards, pp. 65–77, and discussion, pp. 77–87. In P.O.Fanger, editor; and O.Va̸lbjorn, editor. , Eds. Indoor Climate. Effects on Human Comfort, Performance, and Health in Residential, Commercial, and Light-Industry Buildings. Proceedings of the First International Indoor Climate Symposium, Copenhagen, August 30–September 1, 1978. Copenhagen: Danish Building Research Institute, 1979.

5.

Andrews, F.T. Building Mechanical Systems, pp.117–124. New York: McGraw-Hill Book Company, 1977.

6.

Arguelles, A.E., D.Ibeas, J.P.Ottone, and M.Chekherdemian. Pituitary-adrenal stimulation by sound of different frequencies. J. Clin. Endocrinol. Metab. 22:846–852,1962. [PubMed: 13862213]

7.

Austin, P.R., and S.W.Timmerman. Design and Operation of Clean Rooms 1965, pp.96–135. Birmingham, Mich.: Business News Publishing Company, 1965.

8.

Axelsen, O. Influence of heat exposure on productivity. Work Environ. Health 11:94–99,1974. [PubMed: 4456895]

9.

Benson, F.B., J.J.Henderson, and D.E.Caldwell. Indoor-Outdoor Pollutant Relationships: A Literature Review. U.S. Environmental Protection Agency (National Environmental Research Center) Publication No. AP-112. Washington, D.C.: U.S. Government Printing Office, 1972. 73 pp.

10.

Berglund, L.G. New horizons for 55–74: Implications for energy conservation and comfort. ASHRAE Trans. 86 (Pt. 1):507–515,1980.

11.

Berglund, L.G., and R.R.Gonzalez. Application of acceptable temperature drifts to built environments as a mode of energy conservation. ASHRAE Trans. 84 (Pt. 1):110–121,1978.

12.

Binder, R.E., C.A.Mitchell, H.R.Hosein, and A.Bouhuys. Importance of the indoor environment in air pollution exposure. Arch. Environ. Health 31:277–279,1976. [PubMed: 999338]

13.

Boyce, S. Reflections on a clean glass building, pp. 36–37. In Maintenance Guide for Commercial Buildings. Cedar Rapids: Stamats Publishing Co., 1975.

14.

Bradley, E.C., and A.J.Haagen-Smit. The application of rubber in the quantitative determination of ozone. Rubber Chem. Technol. 24:750–755,1951.

15.

Broadbent, D.E. Noise in relation to annoyance, performance, and mental health. J. Acoustical Soc. America 68:15–17,1980. [PubMed: 7391357]

16.

Cain, W.S. Contribution of the trigeminal nerve to perceived odor magnitude. Ann. N.Y. Acad. Sci. 237:28–34,1974. [PubMed: 4529464]

17.

Cain, W.S. Lability of odor pleasantness, pp. 303–315. In J.H.A. Kroeze, editor. , Ed. Preference Behaviour and Chemoreception. London: Information Retrieval Ltd., 1979.

18.

Cain, W.S., L.G.Berglund, R.A.Duffee, and A.Turk. Ventilation and odor control: Prospects for energy efficiency. Lawrence Berkeley Laboratory Report LBL-9578. Berkeley, Cal.: Lawrence Berkeley Laboratory, Energy and Environment Division, 1979. 61 pp.

19.

Corn, M. Adhesion of particles, pp. 359–392. In C.N.Davies, editor. , Ed. Aerosol Science. New York: Academic Press, Inc., 1966.

20.

Daines, R.H., D.W.Smith, A.Feliciano, and J.R.Trout. Air levels of lead inside and outside of homes. Ind. Med. 41(10):26–28,1972. [PubMed: 4508864]

21.

Darling, W.E. A lot more of what you're looking for on carpet care, pp. 22–25. In Maintenance Guide for Commercial Buildings. Cedar Rapids, Iowa: Stamats Publishing Company, 1975.

22.

Davies, C.N. Deposition from moving aerosols, pp. 393–446. In C. N.Davies, editor. , Ed. Aerosol Science. New York: Academic Press, Inc., 1966.

23.

Dunn, B.E. The noise environment of man, pp. 193–257. In H.W. Jones, editor. , Ed. Noise in the Human Environment. Vol. 2. Edmonton, Alberta: Environment Council of Alberta, 1979.

24.

Fanger, P.O. Thermal Comfort. Analysis and Applications in Environmental Engineering. Copenhagen: Danish Technical Press, 1972. 244 pp.

25.

Fuchs, N.A. The Mechanics of Aerosols, p. 362. New York: Pergamon Press, 1964.

26.

Geber, W.F., T.A.Anderson, and B.Van Dyne. Physiologic responses of the albino rat to chronic noise stress. Arch. Environ. Health 12:751–754,1966. [PubMed: 5938577]

27.

Geen, R.G., and E.C.O'Neal. Activation of cue-elicited aggression by general arousal. J. Personality Soc. Psychol. 11:289–292,1969. [PubMed: 5784269]

28.

Gieseke, J.A., E.R.Blosser, and R.B.Reif. Collection and characterization of airborne participate matter in buildings. ASHRAE Trans. 84(Pt. 1):572–589,1978.

29.

Glass, D.C., and J.E.Singer. Urban Stress. Experiments on Noise and Social Stressors. New York: Academic Press, Inc., 1972. 182 pp.

30.

Hermance, H.W., C.A.Russell, E.J.Bauer, T.F.Egan, and H.V. Wadlow. Relation of airborne nitrate to telephone equipment damage. Environ. Sci. Technol. 5:781–785,1971.

31.

Hunt, C.M. Simple Observations of Some Common Indoor Activities as Producers of Airborne Particulates. Paper presented at ASHRAE Symposium on Cleaner Indoor Air—Progress and problems C1–72–1, Cincinnati, Ohio, October 19–22, 1972.

32.

Jovanović, U.J. Normal Sleep in Man. An Experimental Contribution to Our Knowledge of the Phenomenology of Sleep. Stuttgart: Hippokrates Verlag Gmblt., 1971. 327 pp.

33.

Kasl, S.V. The effects of the residential environment on health and behavior: A review, pp. 65–127. In L.E.Hinkle, Jr., editor; , and W.C. Loring, editor. , Eds. The Effect of the Man-Made Environment on Health and Behavior. DHEW Publication No. (CDC) 77–8318. U.S. Department of Health, Education, and Welfare, Center for Disease Control. Washington, D.C.: U.S. Government Printing Office, 1977.

34.

Kryter, K.D. The Effects of Noise on Man. New York: Academic Press, Inc., 1970. 633 pp.

35.

Lebowitz, M.D. A critical examination of factorial ecology and social area analysis for epidemiological research. Ariz. Acad. Sci. 12(2):86–90,1977.

36.

Lebowitz, [M.] D. Social environment and health. Public Health Rev. 4:327–351,1975. [PubMed: 10297832]

37.

Lebowitz, M.D. The relationship of socio-environmental factors to the prevalence of obstructive lung diseases and other chronic conditions. J. Chron. Dis. 30:599–611,1977. [PubMed: 903391]

38.

Lehmann, G., and J.Tamm. Über Veränderungen der Kreislaufdynamik des ruhenden Menschen unter Einwirkung von Geräuschen. Int. Z. Angew. Physiol. einschl. Arbeitsphysiol. 16:217–227,1956. (in German: ) [PubMed: 13376178]

39.

Lennard-Jones, J.E.Cohesion. Proc. Physical Soc. ( London: ) 43:461–482,1931.

40.

Lin-Fu, J.S. Vulnerability of children to lead exposure and toxicity (First of two parts). N. Engl. J. Med. 289:1229–1233,1973, [PubMed: 4784897]

41.

Mathews, K.E., Jr., and L.K.Canon. Environmental noise level as a determinant of helping behavior. J. Personality Soc. Psychol. 32:571–577,1975.

42.

McNall, P.E., Jr. The relation of thermal comfort to learning and performance: A state-of-the-art report. ASHRAE Trans. 85 (Pt. 1), 759–767,1979.

43.

Moschandreas, D.J., J.W.Winchester, J.W.Nelson, and R.M. Burton. Fine particle residential indoor air pollution. Atmos. Environ. 13:1413–1418,1979.

44.

National Center for Health Statistics. Medical Care, Health Status and Family Income. Series 10, No. 9. Washington, D.C.: U.S. Government Printing Office, 1964.

45.

Nemecek, J., and E.Grandjean. Results of an ergonomic investigation of large-space offices. Human Factors 15:111–124,1973.

46.

New York State Commission on Ventilation. Ventilation. New York: Dutton, 1923.

47.

Penney, G.W., and N.G.Ziesse. Soiling of surfaces by fine particles. ASHRAE Trans. 74(Pt. 1):VI.3.1–VI.3.13 , 1968.

48.

Pepler, R.D. A study of productivity and absenteeism in an apparel factory with and without air conditioning. ASHRAE Trans. 79(Pt. 2) : 81–86,1973.

49.

Pepler, R.D., and R.E.Wamer. Temperature and learning: An experimental study. ASHRAE Trans. 74(Pt. 2):211,1968.

50.

Proshansky, H.M., W.H.Ittelson, and L.G.Rivlin. The influence of the physical environment on behavior: Some basic assumptions, pp. 27–37. In H.M.Proshansky, editor; , W.H.Ittelson, editor; , and L.G.Rivlin, editor. , Eds. Environmental Psychology: Man and His Physical Setting. New York: Holt, Rinehart and Winston, Inc., 1970.

51.

Radford, E.P. Health aspects of housing. J. Occup. Med. 18:105–108,1976. [PubMed: 1249663]

52.

Russell, F.A.R. The Atmosphere in Relation to Human Life and Health. Publication No. 1072. Washington, D.C.: Smithsonian Institution, 1896. Compiled in Smithsonian Misc. Collections 39:Article III, 1899. 148 pp.

53.

Sacher, G.A. Energy metabolism and thermoregulation in old age. ASHRAE Trans. 85(Pt. 1):775–783,1979.

54.

Schaefer, V.J., V.A.Mohnen, and V.R.Veirs. Air quality of American homes. Science 175:173–175,1972. [PubMed: 5008435]

55.

Schaffer, E.L. A survey of some moisture and other problems influenced by building tightness. ASTM-DOE Symposium on Air Infiltration and Air Change Rate Measurement, Washington, D.C., March 16, 1978 (in press).

56.

Schaplowsky, A.F., L.G.Polk, F.B.Oglesbay, J.H.Morrison, R. E.Gallagher, and W.Berman. Carbon monoxide contamination of the living environment: A national survey of home air specimens and children's blood samples. Presented at American Public Health Association Meeting, November 7, 1973. U.S. Department of Health, Education, and Welfare, Center for Disease Control.

57.

Selye, H. The Stress of Life. rev. ed. New York: McGraw-Hill Book Company, Inc., 1976. 516 pp.

58.

Spealman, C.R. Odors, odorants, and deodorants in aviation. Ann. N.Y. Acad. Sci. 58:40–43,1954. [PubMed: 13139333]

59.

Spivey, G.H., and E.P.Radford. Inner-city housing and respiratory disease in children: A pilot study. Arch. Environ. Health 34:23–29,1979. [PubMed: 434922]

60.

Sterling, T.D., and D.M.Kobayashi. Exposure to pollutants in enclosed “living spaces.” Environ. Res. 13:1–35,1977. [PubMed: 66143]

61.

U.S. Department of Health, Education, and Welfare, National Institute for Occupational Safety and Health. National Occupational Hazard Survey. Pilot Study. DHEW (NIOSH) Publication No. 75–162. Washington, D.C.: U.S. Department of Health, Education, and Welfare, May 1975.

62.

U.S. Environmental Protection Agency, Office of Noise Abatement and Control. Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. U.S. Environmental Protection Agency Report No. 550/9–74–004. Washington, D.C.: U.S. Environmental Protection Agency, 1974. 46 pp. + appendices.

63.

Vega, T., and C.J.Seymour. A simplified method for determining ozone levels in community air pollution surveys. J. Air Pollut. Control Assoc. 11: 28–33, 44, 1961. [PubMed: 13780582]

64.

Walker, R.L., and B.R.Fish. Adhesion of Particles to Surfaces in Liquid and Gaseous Environments. Paper presented at 4th Annual Meeting of the American Association for Contamination Control, Miami, Fla., May 25–28, 1965.

65.

Williams, H. Developing a table of relaxation allowances. Ind. Eng. 5(12):18–22,1973.

66.

Williams, H.G. More light with less manpower, pp. 56–68. In Maintenance Guide for Commercial Buildings. Cedar Rapids: Stamats Publishing Co;, 1975.

67.

Wilner, R., R.Walkey, T.Pinkerton, and M.Tayback. The Housing Environment and Family Life. Baltimore: The Johns Hopkins Press, 1962. 338 pp.

68.

Winneke, G., and J.Kastka. Odor pollution and odor annoyance reactions in industrial areas of the Rhine-Ruhr region, pp. 471–479. In J.Le Magnen, editor; and P.MacLeod, editor. , Eds. Proceedings of the Sixth International Symposium on Olfaction and Taste. London: Information Retrieval Ltd., 1977.

69.

Winnick, L. American Housing and Its Use: The Demand for Shelter Space. Census Monograph Series. New York: John Wiley & Sons, Inc., 1957. 143 pp.

70.

Winslow, C.-E.A. Fresh Air and Ventilation. New York: E.P.Dutton & Company, 1926. 182 pp.

71.

Winslow, C.-E.A., and L.P.Herrington. The influence of odor upon appetite. Am. J. Hyg. 23:143–156,1936.

72.

World Health Organization. Health Hazards of the Human Environment. Geneva: World Health Organization, 1972. 387 pp.

73.

Wyon, D.P. Human productivity in thermal environments between 65F and 85F (18–30C), pp. 192–216. In J.A.J.Stolwijk, editor. , Ed. Energy Conservation Strategies in Buildings. New Haven: John B.Pierce Foundation of Connecticut, Inc., 1978.

74.

Wyon, D.P. The role of the environment in buildings today: Thermal aspects. Factors affecting the choice of a suitable room temperature. Build Int. 6:39–54,1973.