Document gbpR94gGMDegwkOwyJ09nkQ5e

'' American Society 0/ Heating a4 Ventilating Engineers Guide `-'I andJ of Atht-e_ dfistrib ut-ion of- th- e air within large rooms. A high id dioxide concentration in parts of an occupied room may indicate air ^ nation which can result in objectionable odors or in failure to ,<>Sta local surplus heat. em' The Petterson-Palmquist apparatus has been generally accepted as standard device for the determination of carbon dioxide in air invest' ^ tions. The principle involved is the measurement of a given volum^3"' air, the absorption of the contained carbon dioxide in a caustic nof solution, and the remeasurement of the volume of air at the orig' ^ Fig. 12. Data Sheet for Synthetic Air Chart Test pressure in a finely, graduated capillary tube, the difference in volume representing the absorbed carbon dioxide. (See Report of Committee on Standard Methods for Examination of Air, American Public Health Asso ciation, Vol. 7, No. 1; American Journal of Public Health, Jan., 1917). Where field, conditions are such that this apparatus may not be con veniently used, as in street cars, air samples may be collected in prepared bottles having rubber stoppers, and these may be subjected to laboratory analysis. Dust The Hill Dust Counter is a simple device with which to measure the number of very large particles of dust in the air, while more exact studies of dust may be. made with the Konimeter, or with the Impinger. (See Public Health Bulletin, No. 144, 1925, U. S. Public Health Service). 416 Chapter 26--`Ventilation Standards her of bacteria which are attached to heavy particles of dust moisture may be determined by the number of colonies that Irbps ot cujture plate which has been exposed for two minutes. A a rr)4-in Petrie dish, with agar-agar for a media, is used for this pndard . teg are jnCubated from 24 to 48 hours at a temperature {uihpse- . the end of this time the separate colonies have de- sjze which are easily counted. If an incubator is not available may be grown at room temperatures (70 deg.) for a period of ffiv|daystrie air measurements must be made with skill and precision great care must be exercised in securing the right conditions under r4> ch such measurements are made. There are two general methods in ' for measuring air volumes, the first, by means of an anemometer, and |fhe second, by means of a Pitot tube. ^Anemometers and Pitot Tubes When it is necessary to employ an anemometer for measuring air flume, the instrument must have been recently calibrated, and the reatest care must be exercised in methods of manipulation. The influence f obstructions at the register face, the distance from the register at which Jie anemometer is held and the great variation in velocities which exists Qover the area of most air discharge openings all combine to make an exact ^quantitative measurement of air by an anemometer a difficult matter. -J For a further discussion of the measurement of air flow by means of fthe anemometer and Pitot tube, see p. 503, Chapter 31. & Movement Determinations fe Air movement is a vital factor in the prevention of stagnant areas and ) bodily discomfort. Where a determination of air movement is desirable i/the Kata-thermometer, as developed by Dr. Leonard Hill, of England, `/may be used. (See Report of Committee on Standard Methods for Exgamination of Air, American Public Health Association, American Journal ibf Public.Health, Vol. 7, No. 1, January, 1917. The wet Kata-thermometer 'gives the rate of cooling by radiation, convection and evaporation. The i^ary Kata-thermometer gives the rate of cooling by radiation and con'4>yection. The difference between the two is the rate of heat loss due solely jRpito evaporation. Air movement is a consideration in the determination - of the effective temperature. Air movement may be determined approximately by observation of the movement of a smoke cloud and the use of a stop watch; the smoke > cloud being formed by means of an ammonium chloride cloud device, or />; ,\-.by a smoke bomb. Carefully balanced gas balloons may also be used. REFERENCES < %. Operondi of the Synthetic Air Chart* by John R. Allen (A.S.H.V.E. Transactions, Vol. 26, ' 'i-y \ -1WUM,opd.e5rn45T).rend in Science of Ventilation, by Perry West (A.S.H.V.E. Journal, June, 1924, p. 421). P l^)fUTKtntS fT lhe Measurement of Air Velocity, by J. H. Parkin (A.S.H.V.E. Journal. June, 1929, 417 iz