On Artificial Lighting in Schools¹

D. D. Bekaryukov and M. I. Korsunskaya (Moscow)

Received 22 August 1932

The question of lighting in schools—or, more precisely, the illumination of classrooms and workrooms—came to occupy a prominent place in school hygiene after the classical studies of Cohn and Erismann, followed by those of a number of other investigators in the second half of the last century, established that a substantial percentage of schoolchildren were nearsighted. It was further observed that this percentage increased with the length of time spent in school and the intensity of schoolwork, from primary through secondary to higher education. Inadequate lighting of classrooms, particularly inadequate artificial lighting, was identified as one of the principal causes of this phenomenon. This is readily understandable when one considers that the artificial lighting technology available to schools serving the general population was then highly unsatisfactory: there were only kerosene lamps with weak flat-wick burners and open gas flames; the only electric devices were arc lamps, which were for practical purposes unusable in schools. Only later, toward the end of the century and at the beginning of the present one, did incandescent mantles for gas and kerosene lighting, and above all electric incandescent bulbs, begin to come into use. These met all hygienic requirements: they provided sufficient luminous intensity, permitted a great variety of arrangements and distributions of light sources, and were entirely harmless to the air quality and temperature of classrooms. In a technically backward country such as the Russian Empire, however, with its paltry appropriations for public education—not to mention the improvement of health conditions in schools—the widespread use of electric lighting was plainly impracticable for most schools. This even led some hygienists working in schools to maintain that schoolwork, particularly in primary schools and for the younger groups, should be confined to the hours of the day when artificial lighting was unnecessary. Such an arrangement is unacceptable in the Soviet school. Faced with the immense task of providing universal advanced education and rapidly training politically educated, technically skilled, and healthy builders of socialist society, the Soviet school cannot exclude from its working hours the times when artificial lighting is required. Nor is there any need to do so: the sweeping electrification of the country makes it possible to use electric lighting not only in cities and large workers’ settlements but, with the development of collective and state farms, in rural schools as well.

¹ This article draws on materials from a research study of artificial lighting in schools in Moscow’s Krasnaya Presnya district, conducted in 1930–31 under the direction of M. I. Korsunskaya, an assistant at the Institute of Social Hygiene, with D. D. Bekaryukov serving as consultant. The study involved physicians of the Krasnaya Presnya OZD; Yu. V. Vadkovskaya and M. Ya. Mirsky, researchers at the Institute of Social Hygiene; I. L. Freidgeim, Yu. I. Grasyuk, and B. O. Aizenshtat of the OZD Institute; and V. K. Varishchev, consultant to the OZD Institute’s hygiene laboratory.

Thus, a real foundation is being laid for a satisfactory solution to the problem of artificial lighting in schools, a problem of particular hygienic importance in Soviet schools. Even now, the number of activities that strain the eyes—reading, writing, drawing, and certain forms of practical work, such as metalworking, cardboard construction, and sewing—remains quite substantial. The content of these activities has changed completely, but the demands they place on vision remain, as does the task of protecting the eyes. We must not overlook the fact that a considerable proportion of visual defects occurs among people in occupations requiring intensive visual work, especially with small objects. According to the figures cited in an article by Dr. Pakhomychev,¹ persistent visual defects are found in 18% of watchmakers, 46% of jewelers, 33% of engravers, 25% of mechanics, and 51% of typesetters, compared with 5% of agricultural workers and 6% of factory workers. All the occupations listed make extensive use of artificial lighting. Although the causal relationship between inadequate lighting and visual defects has not been precisely established, it may nevertheless be regarded as certain that bringing the objects of work too close to the eyes (less than 30 cm), by requiring increased effort from the muscles that converge the eyes and those responsible for accommodation, causes fatigue in these muscles and subsequently various forms of persistent visual defects. Inadequate or improper artificial lighting inevitably leads people to bring their work closer to their eyes, a practice that then becomes habitual.

Besides its hygienic importance, proper lighting also has industrial significance: it increases labor productivity. To avoid burdening the reader with figures, we shall give only two examples. Dr. Trumpaits’s² observations of the work of draw-in workers in textile production showed that, when the illumination of the workpiece was varied between 45, 75, 100, 500, and 1,000 lux, the time required to perform the work decreased in the following proportion: at 45 lux, 100; then 90.5, 87.3, 85.5, and 83.5. The difference between work performed at 45 and 1,000 lux was 16.5%. An article by Professor Posseck in Weyl’s Handbook of Hygiene gives the following results of experiments on schoolchildren. As a test, the subjects were given a particular text to read, and the time spent reading was recorded in seconds. If the average time required to read the text at an illumination of 30 lux is taken as 100, then the time required was 102 at 10 lux, 108 at 6 lux, and 122.5 at 3 lux. The difference was even more pronounced among those with impaired vision (myopes). In subjects with mild myopia (less than 3 D), the time, taken as 100 at 30 lux, increased to 112 at 10 lux, 127 at 6 lux, and 157 at 3 lux. Among those with moderate myopia (3 D or more), the average time required to read the text, taken as 100 at 30 lux, increased to 111 at 10 lux, 146 at 6 lux, and 171 at 3 lux.

¹ A. I. Pakhomychev, “Lighting and Work,” Theory and Practice of Health Education, issue VI.

² Dr. D. Ya. Trumpaits and Engineer Trukhanov, “On the Methodology for Establishing the Relationship between Illumination and Labor Productivity,” Lighting of Industrial Enterprises, Proceedings of the Leningrad Institute of Occupational Hygiene, vol. IV, issue 5.

Experiments conducted at School No. 61 in Moscow’s Krasnaya Presnya district by the physicians Mirsky, Grisyuk, and Freidheim used the Bourdon test to study the efficiency of children’s work under different levels of illumination at their workstations. They showed that when the average illumination was increased from 26 to 57 lux, work efficiency rose by 22%.

Two findings from these data deserve attention: as illumination decreases, there is not only a general decline in productivity but also, first, a rapid fall in productivity below 10 lux and, second, greater sensitivity to declining illumination among myopic children. There is reason to believe that, despite its importance for hygiene and productivity, artificial lighting in schools is inadequate in the great majority of cases. Thus, in a systematic survey of artificial lighting in 45 schools and 159 classrooms in one district of Moscow, staff members of the Institute of Social Hygiene and the Institute of Maternity and Child Welfare concluded that lighting had been installed without a definite plan or sanitary supervision; that lamps were incorrectly positioned in most cases; that the fixtures were unhygienic; that the number of light points was insufficient in 40% of cases; and that the total luminous intensity of the lamps was below the required level in 38% of cases and substantially below it in 6%. A photometric survey of 934 places conducted by Dr. Yu. V. Vatkovskaya found illumination of 25–50 lux in 34% of cases, 15–25 lux in 29%, 10–15 lux in 18%, less than 10 lux in 9%, and more than 50 lux in 10%. Of the 27 classrooms surveyed, only 11 had semi-indirect lighting fixtures, with devices to protect the eyes from excessive brightness; in the others, the lamps were bare or had wholly unsatisfactory tin reflectors. The result was considerable unevenness in illumination across workstations, reaching ratios of 1:10:12 in individual cases; only in 10 classrooms was the unevenness within the permissible limit of 1:4. Because there were no light-diffusing devices, illumination at the workstations differed greatly between an empty classroom and one occupied by pupils, whose seated bodies cast shadows. Although the survey cited here was conducted in 1929, there is no reason to believe that conditions have improved substantially in this respect. Clearly, school health inspectors newly taking up their duties will have much to do to bring the provision of artificial lighting in schools into order.

Artificial lighting must satisfy three principal hygienic requirements: (a) provide sufficient illumination; (b) eliminate sharp shadows cast by pupils’ bodies, arms, and heads; and (c) protect the eyes from the direct entry of excessively bright light, such as that from the incandescent filaments of electric lamps and certain other light sources. The first objective is achieved by using lamps of sufficient power, in numbers adequate for the size of the room. Sharp shadows are prevented by diffusing the light through the use of lamps made of frosted or opal glass, or suitable fixtures fitted with such glass; shading of the work surface is addressed by properly directing the light, that is, by correctly distributing the lamps; and, finally, protection of the eyes from bright—

…rays—with counter-shades or counter-reflectors made of frosted or opal glass.

The illuminance standards required for ordinary schoolwork (black on a white background) were proposed as early as the last century by Erismann and Cohn: in view of the limited lighting technology then available, they specified 10 to 25 meter-candles (the same as lux); for very demanding work, 50 lux (sewing black on black, drafting, etc.). With the development of lighting technology, these standards have now been raised considerably. In general, one may follow the standards adopted by the Second Lighting Engineering Congress in 1931, namely: in classrooms, 75 lux on table surfaces, 75 lux on blackboards, and 50 lux on pictures, diagrams, etc. hung on the walls; in reading rooms, 50 lux on tables and 100 lux on drawing boards; in gymnasiums, 30 lux on the floor; in rooms for recreation and meetings, 20 lux on the floor; in passageways, corridors, and on stairs, 15 lux on the floor; the same 15 lux at a height of 1.5 m above the floor in cloakrooms; and 50 lux on the floor in lavatories, as required for the careful maintenance of cleanliness. No standards are specified for the illuminance of workpieces in practical workshop work; reference is made only to the relevant provisional regulations for industrial establishments. As a guide, the standards proposed by the research section of the former Leningrad Provincial Labor Department may be cited: for very fine work—including, among activities practiced at school, fine drafting, embroidery, sewing black on black, etc.—60–100 lux; for fine work—typesetting and drafting, precision mechanics, and weaving with dark fabrics—30–60 lux; for work requiring only the differentiation of large details—fitting and lathe work, joinery, etc.—30 lux. The first figures are the minimum permissible values, the second those recommended. If lamps are in short supply and it is absolutely necessary to limit expenditure on energy, the standard proposed by the commission attached to the Leningrad branch of the Central Electrotechnical Council may be adopted as a temporary illuminance standard, with a view to increasing it at the first opportunity: at least 30 lux for classrooms, specialized rooms, laboratories, and reading rooms; 50 lux for drafting rooms; and 15 lux for recreation and assembly halls. In practice, it is much more convenient to determine the required luminous intensity in candles or watts per square meter of room area, reckoning 1 watt as 1.75 candles. The standards of the lighting engineering commission attached to the Leningrad branch of the Central Lighting Council state that, to obtain an illuminance of 1 lux at a height of 1 m above the floor, 0.32 candle per square meter of floor area is required when lamps are suspended at a height of about 3.5 m. Thus, to obtain the illuminance levels given above, 25 to 35 candles per square meter of floor area will be required. This figure can be reduced somewhat by lowering the lamps to 2.25 m above the tables and distributing them unevenly across the room, concentrating them over the area occupied by worktables. Such a reduction is highly desirable, since economic considerations make it unlikely that more than 15 candles per square meter can be demanded.

The illumination of workstations on table surfaces comes not only from rays directed onto those surfaces through the lower segment of the lamp, but also from rays traveling horizontally and upward. After reflection from the ceiling and the upper part of the walls, these rays considerably increase the illuminance of the work surface. Since reflected rays do not cast sharp shadows, there is no need to pass them through diffusing frosted glass, which in this case needlessly absorbs some of the light. Lamps with a frosted lower segment and a transparent upper segment may therefore be used, or frosted-glass counter-reflectors may be placed beneath the lamp. These counter-reflectors should be broadly flared, with a large radius, because counter-reflectors shaped as substantial segments of spheres with a small radius—such as the very common opal-glass globes—illuminate the ceiling in patches and are of little use. In the common type of fixture known as the “Lucette,” the upward light is also passed through specially curved frosted glass. This produces more uniform illumination in all directions, both horizontal and vertical, but some of the light is absorbed, making it necessary to increase…

total luminous intensity of the lamps. The rays from the upper segment of a lamp can also be reflected onto the working surfaces of desks by fitting the lamps with broadly flared shades, 70 to 80 cm in diameter at the bottom, with a white reflective surface. Such shades considerably increase the illumination of the working surfaces, but the upper part of the room remains in shadow; if shades of opal glass are used, however, this shading is less pronounced. Besides sufficiently strong illumination of the working surfaces, a more or less uniform distribution of light is also required. It is considered proper for the difference in illumination between locations not to exceed a ratio of \(1:4\); that is, the best-lit places should receive no more than four times the illumination of the poorly lit places. Uneven illumination between different places in a room, however, is not a serious hygienic defect if the illumination at the least-lit places is not below the standard. A serious defect is uneven illumination within a single workplace, which readily occurs when the hands and body of the seated person cast a sharp shadow. According to the lighting congress rules cited above, the illumination of the shaded part of a workplace should not be less than \(0.5\) times that of the unshaded part. Experience shows that, when lamps are improperly positioned, fittings are poorly designed, or no fittings are used, the shading may be much greater.

Since the illumination of the working surfaces of desks is considerably increased by rays reflected from the ceiling and upper walls, their color is important. The ceiling should be white, and the walls should be painted a color that absorbs as little light as possible—preferably light yellow, or white. The ceiling and walls must be kept completely free of dust. The fittings must be kept equally clean, especially their light-transmitting and reflecting surfaces. Likewise, lamps should not be left in use until they burn out, but should be replaced with new ones when they become visibly darkened.

The next hygienic requirement is the elimination of sharp shadows cast on the work by the worker’s hand or body, as occurs in ordinary right-handed work when light comes from the right and behind. As noted above, sharp shadows are softened by the use of diffusing glass—frosted or opal glass; frosted glass is preferable because it obstructs less light. The desired direction of the shadow is obtained when the light comes from the left and front. When several lamps are present, light comes from all sides, but noticeable shadows are cast by the nearest ones. Suitable placement of the lamps can therefore considerably soften shadows falling in unfavorable directions. For hygienic reasons, a room should not be illuminated by one or two lamps, however powerful, since this makes it impossible to avoid shading at places to the left and in front of the source.

The most rational arrangement is to distribute the light among several sources, using four or five lamps with a total luminous intensity of 600–700 candles¹ in a room of 50–40 m², with their placement

¹ When selecting lamps for a classroom, one must of course take into account the availability of the various types of lamps; the figures given should therefore be regarded as approximate guidelines.

…with the desks arranged in three columns facing the teacher’s desk, two lamps may be placed along the center line of the left-hand column, with the front lamp projecting somewhat beyond the front edge of the first desk; a second line may be placed along the longitudinal axis of the room, above the aisle between the second and third columns of desks. A fifth lamp may be placed in the middle of the room.

The simplest way to prevent shadows from falling improperly on the object or work area is, of course, to arrange the worktables not in rows facing forward but in groups—in a circle—with everyone facing the lamp. With modern teaching methods and easily movable furniture, this presents no particular difficulty.

The third requirement—protecting the eyes from the direct effect of excessively bright rays, such as those from the incandescent filaments of electric lamps—is met by using suitable frosted or opal glass, or counter-reflectors made of the same glass. As a general guiding rule, the bright filament or its reflection should not be visible to pupils in any direction of gaze. As an acceptable compromise, when suitable devices and materials are unavailable, clear-glass lamps not shielded by any diffusing glass may be placed high beneath the ceiling (3.0 m), where pupils do not direct their gaze.

Partly to illustrate and partly to substantiate the foregoing, we may cite the results of one part of an experimental study conducted by staff of the Institute of Social Hygiene and the Institute for the Protection of the Health of Children and Adolescents (see above) in a classroom at a Moscow school.

For the experiments, the room, with an area of 44 m² (7 × 3 m) and a height of 3.4 m, was renovated and painted: the ceiling white, the walls light yellow, and the lower wall paneling light gray. A special wire grid was installed beneath the ceiling, enabling various lighting fixtures with lamps of constant wattage to be positioned at specified points and at different heights according to the plan being tested. The school desks, whose working surfaces were used for photometric measurements of illuminance, were arranged in three columns along the long axis of the room, with four intervening spaces—the middle ones 1 m wide and the outer ones 40 cm wide. The arrangement of the desks remained unchanged throughout the experiments. The plan called for a series of tests with different combinations of lamp placement, intensity, suspension height, and fixtures; in practice, only two series could be carried out: one with “Lucette” fixtures,¹ commonly used in new schools under the Moscow Department of Public Education, and one with large lampshades proposed by the author of this note.² Illuminance measurements with luxmeters were made by staff of the hygiene laboratory of the Institute of Health Protection, under the direction of Dr. V. K. Varishchev.

In the test of the “Lucette” fixtures, four fixtures were arranged more or less evenly in a square at a height of 2.65 m above the floor. In one series of experiments, four 50-watt lamps were used (total luminous intensity 350 candles, or 8 candles per m² of floor area); the resulting average illuminance was 25.7 lux, with a maximum of 36 lux and a minimum of 16 lux. The minimum occurred in the corners of the room, especially near the windows. Places with an illuminance of 16 to 25 lux accounted for 40%, and those with 25–36 lux for 60%. With 100-watt lamps, giving a total luminous intensity of 700 candles (15.0 candles per m² of room area), the average illuminance was 39.5 lux, with a minimum of 30 lux and a maximum of 56 lux.

In all cases there were no sharp shadows, and the room was evenly illuminated in all parts and at the workstations (a ratio of 1:2). These results show that the hygiene requirements concerning the absence of sharp shadows, uniformity of illumination, and protection of the eyes from excessive brightness were met; unmet…

¹ The Lucette fixture consists of a completely enclosed cavity of distinctive shape, containing the lamps. The walls of the cavity are made of frosted glass; the lower surface is a segment of a sphere.

² Handbook for Physicians on the Protection of the Health of Children and Adolescents, Bekaryukov’s article “The School Building,” p. 86.

… remains the principal requirement: adequate illumination, which even in the second series of experiments does not reach the standards cited by the Second Congress.

In the second series of experiments, widely flared cardboard shades with a white reflecting surface and a lower opening 80 cm in diameter were used to increase illumination. Clear lamps were used in one set of trials and semi-frosted lamps in another. The lamps were placed in the center of the shade, 10–15 cm above its rim. Only 50-watt lamps were tested. Five 50-watt lamps with a combined luminous intensity of 350 candlepower (8 candlepower per m² of floor area), arranged in a square with the fifth lamp in the center, produced strong but harsh and uneven illumination: 30 lux in the corners and 200 lux in the center of the room. With five semi-frosted lamps of a combined luminous intensity of 437 candlepower (10 candlepower per m²), suspended at a height of 2.15 m, the average illumination was 80 lux, ranging from 35 to 180 lux.

In the latter case there were no harsh shadows, but the upper part of the walls and the ceiling remained in shadow. It may be expected that certain changes in the arrangement of the lamps—for example, moving the outer lamps of the square closer to the walls and replacing the central 50-watt lamp with a 75-watt lamp—would provide more uniform illumination of the workstations without reducing average illumination. Unfortunately, the experiments were not continued. If the difference between the cost of the Lucette fixtures and that of the shades when mass-produced is taken into account (probably no less than 10 rubles per fixture), the economic advantage of using simpler fixtures becomes apparent. Only the shadowing of the ceiling remains unavoidable, but this drawback is of little hygienic significance and can be tolerated, especially in view of the higher illumination achieved with lower energy expenditure: 8 and 10 candlepower per m² instead of 15.1.

The research methodology may be regarded as sound, and it is desirable that the experiments be continued, since only experimentation can determine the most rational combinations of light-source placement, lamp type, and fixture type, without which standardization and mass production are impossible.