Coupon Accepted Successfully!



  1. Uses: provides life giving oxygen, cooling of the body, functioning of special senses of the body like smel & harring.
  2. Daily Requirement: 10 – 20 cubic meter per day.
  3. Impurities in Air: Due to combustion, respiration, trade, traffic & manufacturing process etc.
  4. Self Cleansing mechanisms: wind, sunlight, rain & plant life.
  1. Indices of thermal comfort
    1. Air temperature: it’s an inadequate measure.
    2. Air temp. and humidity: even this was found to be unsatisfactory.
    3. Cooling power: air temp. and humidity were considered along with the air movement and together called as ‘cooling power’. It is measured by Kata thermometer.
    4. Effective air temperature(ET): it is in arbitrary index which combines in a single value the effect of temp., humidity, and movement of internal air on the sensation of warmth or cold felt by the human body. Thus an ET of 30deg C in an environment implies that the subjective sensation will be the same as that in a saturated atmosphere of30deg C with no air movement.
    5. Corrected ET (CET): this is an improvement over ET as it also takes into account the radiant heat. Thus if a source of radiation is present, it is better to take CET. It is obtained from prepared nomograms by reference to the globe thermometer.
    6. McArdle’s maximum allowable sweat rate: a value of 3 litres is considered as upper limit of comfort zone and 4.5 litres as maximum in a period of 4 hours.
    7. Comfort zones: the range of ETs overwhich majority of adults feel comfortable i.e. maintain normal balance b/w production & loss of heat at normal body temp & without swetaing.
    8. Comfort Zones evaluated in India 


CET in deg C

a.       Pleasant & cool



b.       Comfortable & cool



c.       Comfortable



d.       Hot & uncomfortable



e.       Extremely hot



f.        Intolerably hot






g.       Comfort zone



h.       Just tolerable



i.        Intolerable



  1. Measurement of humidity:  dry & wet hygrometer, Sling psychrometer and Assmann psychrometer.
  2. Measurement of air velocity: Anemometer.
  3. Overcrowding criterion:
    1. Persons per room
      1 room 2 persons, 2 rooms 3 persons, 3 rooms 5 persons, 4 rooms 7 persons & 5 or more rooms 10 persons (additional 2 for each further room).
    2. Floor space
      110 sq. ft 2 persons, 90-110 sq. ft 1½ persons, 70-90 sq. ft 1 person.
      50 –70 sq. ft. ½ person and under 50 sq. ft. nil.
      A baby< 12 months is not counted and 1-10 years is ½ unit.
    3. Sex separation.
      2 persons more than 9 years of age, not husband & wife, of opposite sex have to sleep in a single room.
  1. Air pollution
    1. Main sources of air pollution are automobiles and industries.
    2. Major air pollutants are – CO, SO2, lead, particulate matter, CO2, hydrocarbons, HS, ozone.
    3. Lead pollution comes mainly from the vehicles. SO2 comes mainly from combustion of sulphur containing fuels and in industrial processes. CO is most common and widely distributed air pollutant, it comes mainly from incomplete combustion of carbon containing materials e.g. fuels, industrial processes etc.
    4. Best indicators of air pollution are SO2, suspended particulate matter (SPM), and smoke and oxides of nitrogen. 




Carbon Mono oxide

Motor vehicle

Sulphur dioxide

Industrial process

Hydrogen sulphide

Burning refuse

Organic sulphide

Noxious Agent of Air pollution




Adverse effect

Oxides of


Automobile exhaust, gas stove & heaters, wood burning stoves, kerosene space heaters

Respiratory tract irritation, bronchial hyperactivity, impaired lung defenses, bronchiolitis obliterans.


Automobile exhaust, cigarette smoke

Lung cancer



Automobile exhaust, high altitude aircraft cabin

Cough, substernal bronchoconstriction, decreased exercise performance, respiratory tract irritation.



Power plant, smelters, oil refineries, kerosene space heaters

Exacerbation of asthma & COPD, respiratory tract irritation


Automobile exhaust using leaded gasoline

Impaired neuro-physiological development of children

  1. Ventilation
    1. Cubic feet space per hour per person for air change is 300-3000.
    2. Air change
      1. Living room: 2-3air change in one hour.
      2. Work room: 4-6 air changes in one hour.
      3. > 6 / hourdrought.
    3. Space per person is 1000-1200 c.ft.
    4. Optimum floor space per person: 50-100 sq. ft.
Types of ventilation:
    1. Natural ventilation
    2. Wind
    3. Diffusion
    4. Inequality of temperature
Disadv: not possible to regulate the velocity of incoming air nor to adjust its temp or humidity.
  1. Mechanical ventilation
    1. Exhaust ventilation
    2. Plenum ventilation: fresh air is blown in room by centrifugal fan and vitiated is removed.
    3. Balanced ventilation: Exhaust ventilation + Plenum ventilation.
    4. Air conditioning: control of temperature, humidity, air movement, distribution, dust, bacteria, odour and toxic gas.

Test Your Skills Now!
Take a Quiz now
Reviewer Name