Methods of Complex Estimation of Microclimate

The main goal is a complex estimation of microclimate according to one parameter.

Several methods of microclimate estimation are distinguished.

Catathermometry

This method was offered by American scientist Hill in 1916. It is based on speed of cooling a heated body depending on 3 factors of microclimate. A catathermometer is a model of a human body heated up to 36.6°C. The cooling ability of air (H) is determined by the formula:

 

H = F / t (millicalories/cm2/sec)

 

(F — factor of catathermometer — a specific heat emission, t — time of cooling a catathermometer from 38°C to 35°C in seconds).

The normal H is 5.5-7 mCal/cm2/sec. If this value is less, it is hot and stuffy, if it is higher, then it is cold. This method is now applied for measuring small speeds of air movement by Hill’s formula.

Method of Effective Temperatures (ET)

It was developed for USA Navy (submarines, etc.). The microclimate was estimated by a thermal state of a person at mass examination of seamen in a special chamber with the following parameters of microclimate: Е (humidity) = 100 %; V (speed of air movement) = 0 m/sec; only the parameter of air temperature was variable.

A comfort zone of thermal state of people upon these conditions makes up 17.2-21.7° EТ. A line of comfort is 18.1-18.9° EТ.

The effective temperatures are determined by nomograms or tables with the help of indications of dry and damp thermometers and speed of air movement.

The further modification of this method is the methodof equivalent-effective temperatures (EE Т). Additional chambers were created where Е (humidity) or V (speed of air movement) changed in such a way that the thermal state of a person corresponded to EТ in a comfort zone. As a result tables were developed for automatic air conditioning via computer.

Application of Methods of Complex Estimation of Microclimate

Methodsof complex estimation of microclimate are used in the following situations:

· At conditioning premises while staying indoors for a long time — spacecrafts, planes, submarines.

· In balneology — for dosing air procedures.

· For improvement of hygienic working conditions in hot workshops of industrial enterprises.

Apart from this, microclimate can be estimated by thermal state of people staying in a given premise with the help of:

· a questionnaire technique — interrogation of people in a premise about their thermal state of health — a 7-point scale of heat sensation exists (but many people are required for examination),

· method of skin (dermal) temperatures by means of electrothermometer:

Table 26

Temperature	Temperature of the forehead skin (t1)	Temperature of dorsum of hand (t2)	t1 — t2	Thermal sensation
10	31.2	24.2	> 6	cold
20	33.5	29.1	3 — 4	comfort
30	35.3	33.1	2.2	hot
35	35.8	35.6	< 1.5	very hot

 

· Technique of perspiration measurement — by electroresistibility of skin, by means of special dyes.

Recommendations for Practical Classes on the Theme

Lesson No. 1.

Hygienic Requirements to Factors of Microclimate

Key Questions

1. Concept of climate and microclimate.

2. Hygienic significance of air temperature and rules of its measurement.

3. Hygienic significance of air humidity and methods of its estimation.

4. Hygienic significance of speed of air movement and methods of its estimation.

5. Characteristics of microclimate of hospital wards and operating rooms, and other premises.

6. Concept of “wind rose”, its hygienic estimation.

Learning Objectives and Their Concrete Definition

1. To know devices for estimation of air temperature and humidity. To get acquainted with a technique of estimation of air temperature and humidity in premises.

2. To know the design and rules of work with devices for estimation of temperature in degrees by Celsius: the minimal thermometer; the maximal thermometer; the household thermometer; the electronic thermometer; thermograph (see Appendixes).

3. The estimation of air humidity is carried out with the help of Assman’s and August’s psychrometer with application of formulas and psychrometric tables.

4. Devices for estimation of speed of air movement. A technique for estimation of air movement speed in a lecture-room. Design and rules of work with devices for estimation of air movement speed. Anemometer.

5. Method of construction of “wind rose” and its hygienic estimation.

Concept of "Wind Rose"

Winds blow permanently in atmosphere. The direction of wind may be: northeast, north, north–west, west, south–west, south, south–east, east. The direction of wind is indicated by a point whence the wind blows.

 

Fig. 17. The construction of "Wind Rose"

 

Example:

 

Graphic presentation of the primary direction of air movement in a given area is called a "wind rose". The direction of wind begins in the center of the picture. Points of the wind direction are connected with a line. In this picture the wind blows from the east more often.

Scientists use the "wind rose" at constructing industrial enterprises, hospitals, houses. Industrial enterprises must be constructed in a town zone where winds blow least of all.

Example:

Where must the industrial enterprises, hospitals, apartment houses be constructed?

Solution

Industrial enterprises must not be constructed in the east of town. They must be constructed in other town zones (north-east, west, south). In this case the town will not be polluted with industrial wastes. Hospitals must be constructed in the east of the town (the cleanest zone of the town). Blocks of flats must be constructed in the north, north–west, south–west, south–east, east of the town.

Self Test

1. Which of the following devices are used for estimation of humidity? (More than one answer may be correct)

*A. Psychrometer

B. Thermograph

*C. Hygrometer

D. Anemometer

E. Wind vane

2. The optimal norm of relative humidity for premises is:

*A. 40-60%

B. 30-70%

C. 10-30%

3. In the classroom on the 5th lesson the following parameters of microclimate have been found out: temperature — 25°С, relative humidity — 79 %, speed of air movement — 0.1m/sec. What physiological parameters testify to unfavorable effect of microclimate on a functional condition of the pupils’ nervous system?

*A. parameters of capacity for work and chronoreflexometry

B. pulse, respiratory rate, vital capacity of the lungs

C. parameters of capacity for work

D. body temperature, chronoreflexometry

4. In which operating room is microclimate for the operating surgeons more favorable?

*A. temperature — 23°C; relative humidity — 40 %; speed of air movement — 0.03 m/sec

B. temperature — 25°С; relative humidity — 45 %; speed of air movement — 0.09 m/sec

C. temperature — 23°С; relative humidity — 40 %; speed of air movement — 0.1 m/sec

D. temperature — 24°С; relative humidity — 30 %; speed of air movement — 0.05 m/sec

E. temperature — 25°С; relative humidity — 50 %; speed of air movement — 0.08 m/sec

5. The relative humidity of air in a hospital ward meets the requirements of hygienic norm. Choose the optimal value.

*A. 30 — 60 %

B. 30 — 70 %

C. 30 — 80 %

D. 20 — 40 %

E. 20 — 50 %

Problem Solving

1. On inspection of conditions of patients’ staying in the hospital the following has been established: the area of a single-bed ward is 6 m2, an average air temperature — 18° C, humidity — 60 %, speed of air movement — 0.18 m/sec. Give a hygienic estimation of microclimate in the ward.

2. In city N. the engineering plant is being constructed. According to a long-term observation the recurrence of winds makes up (in percentage): N — 14, NE — 5, E — 2, SE- 6, S- 19, SW — 26, NW — 18. Specify the optimal direction of the engineering plant location in relation to the built-up area of the city.

Standard Answers:

1. The microclimate in the ward is satisfactory; all the parameters correspond to the hygienic norms.

2. East, as the recurrence of winds from the east direction was equal to 2 %, that is the least value.

 

Lesson No 2.