Document MMYjkXm7p2dVDyjmzndXprQ5j

Heating Ventilating Air Conditioning Guide 1939 open. However, the A.S.H.V.E. Code for Heating and Ventilating Garages, adopted in 1929 and revised in 1935, states that natural venti lation may be employed for the ventilation of storage sections where it is practical to maintain open windows or other openings at all times. The code specifies that such openings shall be distributed as uniformly as pos sible in at least two outside walls, and that the total area of such openings shall be equivalent to at least 5 per cent of the floor area. The code further states that where it is impractical to operate such a system of natural ventilation, a mechanical system shall be used which shall provide for either the supply of 1 cu.ft of air per minute from out-of-doors for each square foot of floor area, or for removing the same amount and discharging it to the outside as a means of flushing the garage.6 Research Research on garage ventilation undertaken by the A.S.H.V.E. Com mittee on Research at Washington University, St. Louis, Mo., and at the University of Kansas, Lawrence, Kans., in cooperation with the A.S.H. V.E. Research Laboratory, and at the A.S.H.V.E. Research Laboratory has resulted in authoritative papers on the subject. Some of the conclusions from work at the Laboratory are listed in the following statements: 1. Upward ventilation results in a lower concentration of carbon monoxide at the breathing line and a lower temperature above the breathing line than does downward ventilation, for the same rate of carbon monoxide production, air change and the same temperature at the 30-in. level. 2. A lower rate of air change and a smaller heating load are required with upward than with downward ventilation. 3. In the average case upward ventilation results in a lower concentration of carbon monoxide in the occupied portion of a garage than is had with complete mixing of the exhaust gases and the air supplied. However, the' variatibns in concentration from point to point, together with the possible failure of the advantages of upward ventilation to accrue, suggest the basing of garage ventilation on complete mixing and.an air change sufficient to dilute the exhaust gases to the allowable concentration of carbon monoxide. 4. The rate of carbon monoxide production by an idling car Is shown to vary from 25 to 50 cfh, with an average rate of 35 cfh. 5. An air change of 350,000 cfh per idling car is required to keep the carbon monoxide concentration down to one part in 10,000 parts of air. Code for Heating and Ventilating Garages (A.S.H.V.E. Transactions, Vol. 35. 1929, p. 355), (A.S. H.V.E. Reprint. January, 1935). Airation Study of Garages by W. C. Randall and L. W. Leonhard (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 233). A.S.H.V.E. Research Report No. 874--Carbon Monoxide Concentration in Garages, by A.S. Langsdorf and R. R. Tucker (A.S.H.V.E. Transactions. Vol. 38. 1930, p. 511). A.S.H.V.E. Research Report No. 935--Carbon Monoxide Distribution in Relation to the Ventilation of an Underground Ramp Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38. 1932, p. 439). . A.S.H.V.E. Research Report No. 934--Carbon Monoxide Distribution in Relation to the Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932, p. 424). A.S.H.V.E. Research Report No. 967--Carbon Monoxide Distribution in Relation to the Heating and Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Trans actions, Vol. 39, 1933, p. 395). Carbon Monoxide Surveys of Two Garages, by A. H. Sluss, E. K. Campbell and Louis M. Farber (A.S.H.V.E. Transactions, Vol. 40, 1934, p. 263). 696 Chapter 36. Natural Ventilation PROBLEMS IN PRACTICE X What factors may make the adoption of a system of ventilation depending upon wind movement inadvisable in new construction? a Variation in direction of wind, j Variation in wind velocity. c. Inability to clean incoming air. j Inability to control location, size and shape of buildings on adjacent property. e Unsatisfactory warming of incoming air during cold weather. 2 0 a. What factors are important in the location and control of ventilating openings? b. What types of ventilating openings are best suited to a projier distribu tion of the air supplied? a. The proper distribution of air as required by the occupants and usage, and the best utilization of natural ventilating forces. The general rules referred to in this chapter apply particularly to these factors. j Windows with swinging sash and openings with deflectors may be used to direct air to the points desired. 3 0 a. What is the best location for ventilating openings? b. How are the sizes of ventilating openings determined for proper air supply? o. Inlet openings should be low and facing the prevailing winds where possible. openings should be high and on the side opposite the prevailing winds. b. For simple openings use Formula 1: Q = EAV Outlet and for stacks use Formula 2: <2 = 9.4 A V H (i - fo) The use of these formulae is illustrated in Example 1 of the text of this chapter. Inlet and outlet areas should be approximately the same for best results. 4 0 a. What are the advantages of roof ventilators? b. How. are proper sizes determined for roof ventilators? a. Roof ventilators offer the best utilization of the inductive force of the wind, and they may be very economically fitted with built-in fans to supply the necessary circulation when the force of the wind is not sufficient. b. Because of the many factors affecting the flow through roof ventilators no accurate formula can be given. It is usual practice to make the combined throat area of all roof ventilators between one-half area and full area of the air inlets as determined by Formula 1. 5 0 What methods of control are used in ventilating systems? Hand control, control by a thermostat located in the ventilated space or in the venti lator, or wind velocity control designed to keep the air discharge constant regardless of wind velocity. 6 0 How is the quantity of air required for a building determined? Sufficient air must be supplied to carry away the heat and impurities generated within a building. The temperature rise and concentration of impurities in the exhaust air must be held within specified limits. (See Example 1 in the text of this chapter). 7 0 What measurements are necessary to determine the capacity of a venti lating system? Wind velocity and air velocities through openings, determined by suitable anemo meters; outdoor air temperatures, measured by a shaded thermometer not near objects 697