TESTS OF VENTILATION 193 



noting presence of odor as none, faint, marked, or strong. 

 Record size of room in cu. ft., number of persons occupying it, 

 method of heating and ventilating, number of ventilators open 

 (windows, doors, registers, transoms, etc.) and movement of 

 air through each as to direction * and strength. Make diagram 

 of essential features. 



[b) By chemical analysis: Use C0 2 apparatus according to 

 directions accompanying same. 2 Make plans of rooms and 

 carry out as in a).] 



2) Air currents: * 



a) Direction: By means of the suspended tuft of down, 

 determine the direction of air movement in various parts of a 

 room. Indicate currents upon diagram of room by means of 

 arrows. 



b) Velocity: Determine by measuring distance in feet that 

 a tuft of down will move with air current in 1 second. 4 



c) Amount: Determine by measuring areas of air inlets 

 and outlets in square feet and multiplying this by the air 

 velocity in feet per second. 



d) Adequacy of air supply: Add together amounts of air 

 entering inlets of room; divide result by total number of oc- 

 cupants; compare with standard requirements (|- cu. ft. per 

 sec.). 



3) Humidity of air: Moisten cloth on bulb of psychrometer 

 and whirl in air until readings of 2 thermometers are constant. 



1 The best method of detecting currents of air at ventilators is to 

 attach a bit of down or a feather on a silk thread 15 in. in length 

 to the end of a whip or stick long enough to reach to the top of 

 the room. This will indicate even a slight draft and show whether 

 it is inward or outward. If the draft is very slight, a candle flame 

 or smoke from a joss stick affords the best means of detection. 



2 This method is simple and reliable and does not require a 

 knowledge of chemistry. 



8 Since the currents of air in a room determine the distribution 

 of the incoming fresh air, their study is important to determine 

 whether the air is distributed evenly throughout the room. 



4 The seconds are easily measured by means of a metronome or by 

 a pendulum consisting of a small lead weight suspended by a cord 

 39 in. long from point of suspension to centre of weight, and should 

 be indicated by tapping, so that the one watching the movements 

 of the down may not have his attention distracted by the necessity 

 of watching the pendulum as well. 



