From Big Medical Encyclopedia

AIR EXCHANGE — deaerating from the enclosed space and introduction instead of its pure fresh air. Disturbance of gas composition of air of rooms or its pollution by harmful substances owing to V.'s insufficiency can cause pathological changes in an organism. Distinguish unorganized V. — by infiltration and organized V. — with the help ventilation (see). It is expressed in cubic meters of the air given or deleted from the room for 1 hour of V. can be considered as an independent gigabyte century. the indicator defining quality of the air environment of rooms. Organized V. in residential, public and production buildings shall promote providing in the enclosed space of optimum indicators of gas structure air (see), a warm and moist condition and the ionic mode of the air environment (see. Ionization of air , Air conditioning ). V.'s intensity of rooms is caused by temperature difference of fresh and internal air, a wind pressure, number of storeys of the building, character of the designs protecting it, an internal design, system of natural or artificial ventilation. An indicator of intensity of V. is frequency rate — the relation of volume of the air coming to the room or deleted from it in 1 hour to the internal volume of the room. At the characteristic of frequency rate of V. on inflow it is designated by a sign +, and on an extract he is familiar —.

The fullest impression about qualitative parameters of the air environment of the enclosed space can be gained by means of complex assessment of the environment for what it is recommended to define the ionic mode, extent of existence of products of metabolism of a human body, harmful chemical substances, dust contents, a bacterial obsemenennost, smells.

V.'s frequency rate necessary for providing indoors an optimum condition of the air environment, depends on a cubic capacity of the room, the number of people, intensity of work and character of the emitted harmful substances.

Basic data for calculation of quantity of a fresh induced air for production rooms are the quantity of the vrednost allocated in 1 hour, admissible quantity of vrednost in 1 m 3 air of the room and quantity of the vrednost which are contained in 1 mg of free air. Determination of size not -

obkhodimy V. is made for rooms different according to the destination on the basis of the corresponding calculations. The necessary volume of the fresh fresh air coming to premises at the rate of carbon dioxide gas is determined by a formula:

L = U/(p-p1) m 3 / hour,

where L — the volume of the air arriving in 1 hour in cubic meters; U — the number of liters of the carbon dioxide gas exhaled by the person in 1 hour; r — the admissible content of carbon dioxide gas in air of the enclosed space (0,1%); r1 — the content of carbon dioxide gas in free air of the cities (0,04%).

Necessary size B. for fight against heat releases is determined at the most admissible temperature (shall not exceed normal more than on 1 — 2 °) by a formula:

where L — the volume of the air arriving in 1 hour in cubic meters; and — an expansion coefficient of air (0,00367); ti — the most admissible air temperature indoors; te — temperature of an incoming air; W — amount of heat generated by people, heating devices and other excess heat releases in kilocalories in 1 hour; 0,306 — the specific heat of air in kilocalories.

Size B. for fight against moisture allocations is determined proceeding from a gigabyte. standards of air humidity for a formula:

L = g/(p2-p1) m 3 / hour,

where L — the volume of the air entered in 1 hour in cubic meters; g — amount of the moisture emitted by various sources in grams; r1 — moisture content of an incoming air in grams on 1 m 3  ; r2 — a gigabyte. standard of air humidity indoors in grams on 1 m 3 .

Bibliography: Bochenkova T. D. and Kokorev N. P. Some aspects of hygienic assessment of working conditions in a demon - lantern and windowless buildings, the Gigabyte. work and the prof. having got sick., No. 11, page 40, 1970; Retter E. I. and Strizhenov of S. I. Aerodinamik of buildings, M., 1968; Firsanov V. M. Architecture of civil buildings in the conditions of hot climate, M., 1971, bibliogr.; Hazanov I. S. and Sokolovsky M. S. Sanitary inspection behind ventilation in industrial, public and utility buildings, M., 1970, bibliogr.

Yu. D. Gubernsky.