Spotters in "Environment and Health: Air" for CFM & MPH students

 Air direction:

1. Wind vane/ Wheather vane/ Wheathercock:

Important points:
  • It is an instrument used for showing the direction of the wind.
  • When the wind is sufficiently strong, the head of the arrow or cockerel indicates the direction from which the wind is blowing.
  • The wind vane is placed high enough to avoid wind interference from objects, buildings, and trees like the top of towers, poles, etc.
  • Types-Weathervane, Wind Sock, Digital Wind Vane
  • Benefits: Safety from storms, very helpful in activities like golf and boat sailing.

Air speed:

2. Anemometer:

Important points:

  • It is a device used for measuring wind speed, direction & pressure.
  • A common weather station instrument.
  • Types- Cup, Vane, Hot-wire, Lesser doppler, Ultrasonic, Pin-pong ball, Plate & Tube anemometer
  • Uses: helps indicate a change in weather patterns, such as an approaching storm, which is important for pilots, engineers, and climatologists.

Air/ Atmospheric pressure:

3. Aneroid barometer:

Oakton Aneroid Barometer Aneroid barometer with mm Hg  scale:Spectrophotometers, | Fisher Scientific

Important points:

  • It is an instrument for measuring air pressure as a method that does not involve liquid.
  • It uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper.
  • Uses: Common in homes and in recreational boats but also used in meteorology, mostly as barograph and pressure instruments in radiosondes for detecting any changes in the atmospheric pressure. 
  • More useful in field but requires constant calibration. 

4. Mercury barometer:

Mercury Manometer | University of Toronto Scientific Instruments Collection

Important points:

  • The mercury barometer's design gives rise to the expression of atmospheric pressure in inches or millimeters of mercury (mmHg).
  • It has a vertical glass tube closed at the top sitting in an open mercury-filled basin at the bottom. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir.
  • It is more accurate than Aneroid barometer.

Air Humidity:

5. Mason's hygrometer:

Science Source - Mason's Hygrometer

Important points:

  • A standard hygrometer using the wet bulb and dry bulb method to determine air humidity & air temperature.  
  • Two red liquid-filled thermometers are secured to the plastic scale plates.  
  • Used at most of the meteorological stations. 

6. Sling/ Whirling psychrometer:

Measuring Relative Humidity ~ Sling Psychrometer - WEATHER & CLIMATE ~  GEOGRAPHICAL INVESTIGATION

Important points:

  • It is an instrument that measures the relative humidity and dew point in an area. 
  •  It has two thermometers: a wet bulb and a dry bulb.
  • It works on the premise that evaporation is a cooling process. The drier the air, the more evaporation takes place off of the wet bulb, dropping the temperature on the thermometer.
  • Uses:  For checking humidity level in air-conditioned rooms and installations, to set and check hair hygrometer, in the measurement range of 0 to 100% RH & for measuring wet bulb temperature between 0’C to 180’C.

7. Assman's/ Aspirator psychrometer:

Important points:
  • It serves for measuring the air temperature and the humidity. 
  • Two parallel mounted, equal thermometers with colored petroleum are used.
  •  The dry bulb thermometer is indicating the true air temperature. 
  • The difference in temperature of both thermometers results in the psychrometric depression. 
  • From this, the relative humidity, the dew point temperature, and the vapor pressure of the air may be computed or determined from tables.

8. Electrical hygrometers:

Important points:
  • It helps to measure humidity or dewpoint or managing humidity control.
  • It measures the change in electrical resistance of a thin layer of lithium chloride, or of a semiconductor device, as the humidity changes. 
  • Other hygrometers sense changes in weight, volume, or transparency of various substances that react to humidity.

Air pollution:

9. Air quality index:

Air Pollution: What Is Air Quality Index, How Is It Measured And Its Health  Impact | Swachh Guide

Important points:

  • It is an index for reporting air quality on a daily basis.
  • It has six categories with the element color scheme which is decided by ambient concentration values of air pollutants & their likely health impacts (breakpoints)
  • Objectives- Comparing air quality conditions at different locations/cities, helps in identifying faulty standards and inadequate monitoring programs, helps in analyzing the change in air quality (improvement or degradation) &  informs the public about environmental conditions. 


  1. Park, K. (2019). Park's textbook of preventive and social medicine. 25th. Jabalpur, India: M/S Banarsidas Bhanot.
  2. Kadri AM. (2019). IAPSM's Textbook of Community Medicine. 1st. New Delhi, India: Jaypee Brothers Medical Publishers (P) Ltd.
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