Which of the following  used for recording very low air velocity
Ref. Foundations of Community medicine. Page. 41
 
Kata Thermometer is quiet sensitive to slight air movements as low as 10 feet per minute.
Usually air velocity is measured by an instrument called anemometer, which consists of 4 hemp spherical cups attached to the ends of 2 Crossed metal arms.
The velocity of the wind is indicated on a counter called the cyclometer, placed in the anemometer box.
Globe thermometer
Kata thermometer
Anemometer
Sling psychrometer