Identifying the Parameters of Natural and Artificial Illumination

The aim of this work is to identify the parameters of natural illumination in a classroom by students, i.e. to determine CNI (coefficient of natural illumination), light coefficient (LC), light angleand ventiductangle.

For estimation of sufficiency of natural illumination some parameters are applied. At hygienic estimation of illumination as geometrical parameters the following are used:

· light angle

· ventiductangle

· light coefficient

· premise depth

To lighting technology parameters the following refer:

· Coefficient of natural illumination (CNI)

· Illumination in the specified point of a workplace.

The artificial illumination can be estimated in the following way.

At inspection of premises for the purpose of illumination sufficiency it is necessary to follow the scheme of inspection. All students of the group participate in performing the given task. The course of independent work is drawn up by the proper protocols. In the protocol the following should be reflected:

The task, sequence of its performance (scheme of object inspection).

The obtained results.

Conclusion with hygienic estimation of the received data and recommendations.

Estimation of Natural Illumination

Definition of light angle.

Light coefficient (LC) represents the ratio of glassed-in surface of windows (without frames and window sashes) to the floor area. It is expressed by fraction, which numerator is 1, and denominator — a quotient of dividing the area of premise by the area of a glass surface.

Task:

· To measure the area of all windows of a premise (room).

· To calculate the glassed-in surface of windows, subtracting 25 % of window sash area from the found area.

· To measure the area of the floor.

· To divide the area of a glassed-in surface of windows by the floor area.

For example, the glassed-in surface of 3 windows available in the room makes up 3.6 m2; the area of the floor is equal to 30 m2. Hence, light coefficient = 3.6: 30 = 1: 8.

Determination of light angles.

As the light coefficient does not take into account the shading effect of opposite buildings, trees and various architectural elements, the light angles should be determined.

Determination of light angle.

The light angle is formed by two beams, one of which (horizontal) is drawn from the place of estimation (for example, a table surface) to a window frame, and another — from the same point to the top edge of the window.

 

Task:

· To measure distance across from the middle of the table surface up to the window frame (а) and down from the windowsill up to the top edge of the window (b).

· To find tangent of the light angle, having divided value “a” by value “b”.

· According to the table of tangents (see Table below) to determine the value of the light angle (α˚).

Table 33

Table of Natural Trigonometrical Values of Tangents

α˚	tg α	α˚	tg α	α˚	tg α	α˚	tg α	α˚	tg α	α˚	tg α
1.	0.017	16	0.287	31	0.601	46		61		76	4.01
2.	0.035	17	0.306	32	0.625	47		62		77
3.	0.052	18	0.325	33	0.629	48		63		78
4.	0.070	19	0.344	34	0.675	49	1.15	64	2.05	79
5.	0.087	20	0.364	35	0.700	50		65		80	5.67
6.	0.105	21	0.384	36	0.727	51		66		81
7.	0.123	22	0.404	37	0.754	52		67		82
8.	0.149	23	0.424	38	0.781	53	1.39	68	2.47	83
9.	0.158	24	0.455	39	0.810	54		69		84
10.	0.175	25	0.466	40	0.839	55		70		85
11.	0.194	26	0.488	41	0.869	56		71		86
12.	0.213	27	0.510	42	0.900	57		72	3.07	87
13.	0.231	28	0.532	43	0.933	58	1.60	73		88
14.	0.249	29	0.554	44	0.966	59		74		89
15.	0.268	30	0.577	45	1.000	60		75		90

For example, the height of the window is 2 m (а), the distance from the window to workplace (b) is equal to 3.5 m. Identify the value of light angle α ˚. Hence we find tg α  = 2: 3.5 which according to the table of tangents corresponds to angle of 30 ˚.

Definition of ventiduct angle.

This angleis formed by two lines, the upper one (the same as with the light angle) goes from the place of illumination estimation to the top edge of the window, and the lower one is directed to the highest point of shading object (for example, opposite house). Ventiduct angleis determined by two students. First the angle adjacent to ventiduct angle (b) is defined. The first student, having bent his head to the level of the table, imaginary draws a direct line from the middle of the table surface to the highest point of the opposite building. The second student standing at the window by instructions of the first student fixes by a hand the point of crossing this line with the window glass and measures its distance from the windowsill (а1). Having divided the received value (а1) by distance from the window up to the middle of the table surface (b), they receive tangent of angle b.

For definition of ventiduct angle value (g) it is necessary to find the difference between the light angle (a) and ventiduct angle (b).

For example: a — distance between the windowsill and the point of crossing of imaginary line with a window frame equal to 1.5 m., b — distance from the window to the workplace equal to 3.5 m. Hence: 1.5: 3.5 = 0.428. According to the table of tangents we find angle β = 23˚. Angle γ = 30˚- 23˚ = 7˚.

Estimation of workplace illumination.

The estimation of workplace illumination is carried out by luxmeter (see above).

Determination of premise depth

To determine this coefficient it is necessary to know the height of window from the upper edge to the floor and distance between the external and internal walls (depth of a room). Estimating these parameters, we get the required coefficient, which value in a workplace should be 1: 2.

Determinationof coefficient of natural illumination (CNI)

CNI is the ratio of illumination at a given point of premise (room) to simultaneous external illumination under the conditions of scattered light, expressed in percentage. CNI can be determined experimentally with the help of luxmeter.

CNI = I in. x 100% / I ex., where:

I in.— illumination in the given point of premise (room)

Iex.— illumination outside the premise (room).

Estimation of Artificial Illumination

It is necessary to determine type of sources (character of lamps: incandescent, luminescent; type of lighting fixtures — lamps of direct, scattered, reflected light), amount of lamps and their capacity. The latter should be divided by the area of premise, thus specific capacity of lamps in watt per m2 is received.

Protocol of Independent Student Work

on the topic “Hygienic Estimation of Natural and Artificial Illumination”

I. Hygienic estimation of natural illumination

1. In classroom No___ there are______ windows, colour of walls is ______________, colour of the ceiling is_____________, cleanliness of window glasses is______________, size of piers between windows is _______.

2. Determination of CNI:

External horizontal illumination is _________ lux;

Illumination in a workplace is _________ lux.

CNI is ____________ %.

3. Determination of LC:

The area of glassed-in windows is __________ m2, area of floor is_____ m2. LC = _______.

4. Determination of light angle (drawing and calculations) ___________________.

5. Determination of ventiduct angle (drawing and calculations) ___________________.

II. Hygienic estimation of artificial illumination.

1. In classroom № ____ there is a ________________________ system of illumination, the lamps of a ___________________________type are fixed.

2. Estimation of uniformity of artificial illumination:

Illumination in lux in points cornerwise _______________________.

Ratio of maximal and minimal illumination at a distance of 0.75 m _________, 5 m_______.

3. Estimation of illumination by a calculation method:

Number of lamps is__________, the floor area is_____________ m2.

Specific capacity of lighting fixture is_________ W/m2.

4. Conclusion (to give a hygienic estimation and recommendations on natural and artificial illumination):

Variant 1. The natural illumination of workplace is sufficient (for a classroom the LC is 1:4-1:6, light angle is not less than 27˚, ventiduct angle is not less than 5˚, illumination of workplace is not lower than 150 lux, CNI is not less than 1.5 %).

The artificial illumination is sufficient (not less than 150 lux at incandescent lamps or 300 lux at luminescent illumination).

Variant 2. Natural and artificial illumination of workplace is insufficient (at lower values of such parameters).

Self Test

1. Identify the light coefficient which should be in operating room:

A. 1:10

*B. 1:4

C. 1:8

D. 1:6

E. 1: 9

 

2. Which parameter reflects the value of natural illumination in a workplace?

A. light angle

B. premise depth

C. light coefficient

D. ventiduct angle

*E. CNI

 

3. How many times is the intensity of artificial illumination higher at application of daylight (luminescent) lamps than at use of incandescent lamps?

*A. 2 times

B. 1 time

C. 10 times

D. 3 times

E. 5 times

4. The light coefficient is:

A. the ratio of illumination in the open air to illumination indoors

B. the ratio of light angle to ventiduct angle

*C. the ratio of floor area to the area of windows

D. the ratio of window area to tangent of ventiduct angle

 

5. The total artificial illumination of a school classroom is planned to provide with lamps of a uniformly dispersing type and incandescent lamps. Identify the least value of illumination in lux, which meets the hygienic requirements of artificial illumination for the given type of premises.

A. 200

B. 250

C. 300

*D. 150

E. 350

 

6. Identify the range of ultraviolet radiation which has a bactericidal effect (in nanometers):

A. 315-265

*B. 280-10

C. 380-300

D. 400-315

E. 320-280

Problem Solving

1. The glassed-in surface of 3 windows available in the room makes up 3.6 m2; the area of the floor is equal to 30 m2. Identify the light coefficient.

2. The light exposure in the open air is 40,000 lux, CNI is 2 %. What is the illumination in a workplace?

3. The depth of hospital ward is 5 m, its length is 6 m. In the ward there are 2 windows, which glassed-in area makes up 2.7 m. The height of the top edge of the window is 2.8 m above floor level. Orientation of windows is SE, the walls are of light warm colours. The light angle is equal to 35˚, ventiduct angle — 10˚. Give a complex hygienic estimation of natural illumination in the hospital ward.

Standard Answers:

1. Light factor = 3.6: 30 = 1: 8. It corresponds to norm for the given room.

2. The illumination in a workplace is equal to 40,000:2х100=800 lux.

3. LC = 30:2.7 = 1:10. All other parameters correspond to norm.

 

Theme No 6.

Hygienic Requirements to Drinking Water Quality

Significance of Water for Man

Water is of great physiological, hygienic and economic significancefor man.

Thefollowing types of water consumption are distinguished:

· drinking — this type of water consumption is the most important for the health of population; the most rigid requirements to its quality are established. According to the WHO data 80 % of all diseases on Earth are connected with poor-quality water or with bad sanitary conditions of life caused by deficiency of clear water.

· household — for providing normal sanitary conditions of life of population and prevention of infections. The requirements to its quality are the same as to drinking water.

· recreational — these are reservoirs and water areas used for rest, water sports, etc. The requirements to its quality are rigid.

· balneologic water use includes baths, showers, inhalations, etc. Very high requirements are set to quality of this water.

· industrial — use of water in technological processes in manufacture. There are special requirements to its quality.

· meliorative — irrigation of soils in agriculture, etc. There are special requirements to quality of this water.

· fish-breeding — for cultivation of fish. The requirements here are sometimes even higher than to drinking water because some kinds of fish are very sensitive. On pollution of reservoirs toxicants can accumulate in fish and cause diseases in people.

· transport — water transport, ports, etc.

Problems of Fresh Water on Earth

Only 3 % of water-supply on our planet are fresh water (the rest is seawater) intensively used for the above-stated purposes of water consumption. Thus, resources of fresh waters are located non-uniformly and are sufficient only for 20 % of densely populated areas, in other places there is deficiency of water.

In addition to deficiency, fresh-water reservoirs have the greatest anthropogenic pollution that frequently makes them useless for water consumption.

UNESCO makes prognoses about real threat of water famine for mankind. A cardinal way of solving water problem is desalination of seawater, but this method is very expensive; besides seas and oceans are considerably polluted and on desalination toxic and carcinogenic substances can form.

Physiological Significance of Water

A daily need for water in adult person in normal conditions makes up 2.5-3 l, in a hot climate or on physical exertion — up to 10-12 l/day.

Water performs a structural role — the organism of the adult consists of water for 51-66%, and organism of a child — for 80-90 %.

Besides, water is a weak electrolyte dissociating into ions of Н+ and OH- which are catalysts of biochemical reactions and water is the medium of these reactions.

Hygienic Requirements to Drinking Water