Indoor Air Pollution

1. Indoor Air Pollution
Lecture-1
Mukesh Khare (PhD UK)
Department of Civil Engineering
Indian Institute of Technology Delhi

2. A Common Myth
• Air pollution occurs only outdoors
Or
• In industrial environment

3. Truth!!!!
What is more agreeable than one’s home?
Feeling safe ?
Away from outside pollution ?
Air inside the conditioned space can be substantially
more polluted than outdoor air.

4. Historical Perspective
First indication of indoor contamination – Asbestos pollution, a
carcinogenic substance, discovered by epidemiologists, used in almost
all building materials about 35 years back.Banned due to adverse
health effects NOT considering IAQ.
Concept of IAQ first introduced among scientific community in 1980
due to some occurrences of ‘episodes indoors’.
At central headquarters of EPA building at Washington, D.C.-
more than 100 people fell sick within 15 minutes of entering the
office.
In Los Angeles, CO level in most of the well insulated
buildings was three times greater than the outside level.

5. Outcome
Such episodes indoors in developed nations ended
up with
1. Extensive monitoring programme
development indoors
2. Identification of indoor contaminants
3. Formulation of IAQ models
4. Development of control methodologies
5. Formulation of Indoor Air Contamination
Standards.
6. Identification of ‘Sick Buildings’
7. Investigation of ‘Sick Building Syndrome
(SBS)’

6. What is IAQ??
 IAQ stands for “Indoor Air Quality”.
 It refers to the nature of the conditioned (heat/ cool)
air that circulates throughout space/area, where we
work and live i.e. the air we breathe most of the time
(almost 80 % of the time).

7. What Causes Indoor Air
Pollution??
Air tightness of buildings
Poorly designed air conditioning and
ventilation systems
Indoor sources of pollution
Outdoor sources of pollution

8. Air Tightness in Buildings
Causes inadequate supply of fresh air, as a
result, negative pressure develops, which
causes
 Ground level pollutants, e.g. CO, Radon etc.to be
drawn inside the buildings.
 Release of odor (Bioaerosols) and other pollutants.
 Pull outside polluted air from vents, cracks and
openings and increase dust, pollen etc.
 Causes “Sick Building Syndrome”.

9. Poorly Designed Air Conditioning
Systems
Results into the production of fungi, molds
and other sickness causing microbes.

10. Problems of IAQ
Enclosed spaces inhabited by humans produce
following effects-
 Reduction in oxygen level of spaces.
 Increase in CO2 level.
 Increase in temperature.
 Increase in humidity
 Increase in Bioaerosols and odor

11. Sources of Indoor Air Pollution in a Typical
Office Building

12. Sources of Indoor Air Pollution in a Typical Household

13. Hard Facts
Fresh air contains 21.0% (v/v) O2
Exhaled air contains 17.0% (v/v) O2 and 83.0 % (v/v)
CO2
An adult emits 45 gm sweat / hour containing
bioaerosols.
An adult produces 300 BTU of heat / hour.
Carbon based gaseous pollutants (VOCs) indoors are 2 to
5 times higher than outdoors.

14. Poor IAQ Results

15. Indoor Air Pollutants and Their Health Effects
Pollutant Effects Limits
NO2 Type: Immediate
Causes: irritation to the skin, eyes and throat, cough etc.
0.05 ppm (avg. over one year for 8
hours exposure daily)- EPA
CO Type: Immediate
Causes: headache, shortness of breath, higher conc. May cause sudden
deaths.
9.0 ppm (avg. over 8 hours period)-
EPA
RSPM Type: Cumulative
Causes: Lung cancer
150 µg/ m3 (24 hr. average)
SO2 Type: Immediate
Causes: lung disorders and shortness of breath
0.05 ppm (avg. over one year for 8
hours exposure daily)- EPA
Radon Type: Cumulative
Causes: Lung cancer
>/ 4 pCi/ Litre of indoor air
Formaldehyde Type: Immediate
Causes: irritation to the eyes, nose and throat, fatigue, headache, skin
allergies, vomiting etc.
120 µ g/ cu.m. (continuous
exposure)- ASHRAE
Asbestos Type: Cumulative
Causes: Lung cancer
>/ 2 fibers/ cu.cm. Of the indoor air
(8 hrs. exposure period)- OSHA
Pesticides Type: Immediate
Causes: Skin diseases
-
VOCs Type: Immediate
Causes: Liver, kidney disorders, irritation to the eyes, nose and throat, skin
rashes and respiratory problems.
Not for all VOCs.
For chlordane:
5µ g/cu.m.(continuous exposure))
CO2 Surrogate index of ventilation 1000 ppm
O3 Type: Immediate
Causes: eyes itch, burn, respiratory disorders, lowers our resistance to colds
100 µ g/cu.m (continuous
exposure)- OSHA

16. Pollutants Concentration
reported
Concentrations
of limited or no
concern
Concentration
of concern
Remarks
Respirable
particulates
0.05 – 0.7 <0.1 >0.015 Japanese standard 0.15
mg/m3
CO 1-1.5 <2 >5 Indicator for eye
irritation(only from passive
smoking)
NO2
0.05 – 1 <0.19 >0.32 ----
CO
---- 2% COHb 3%COHb 99.9%
1-100 <11 >30 Continuous exposure
Formaldehyd
e
0.05 – 2 <0.06 >0.12 Long- and Short- term
SO2
0.02 – 1 <0.5 >1.35 SO2
alone, short-term
CO2
500 – 5000 ppm <1000 ppm >1000 ppm Occupancy indicator
O3
600-9000 <1800 >12000 Japanese standard 1800
mg/m3
Asbestos
<10 fibres/m3
≈0 105
fibre/m For long Exposure
WHO Standards
* typical ranges of concentration is given in mg/m3
, unless otherwise indicated

17. Parameters Affecting IAQ
 Rate of exchange of air from outdoors (ventilation)
 Concentration of pollutants in outdoor air
 Rate of emission from sources indoors
 Rate of removal of pollutants (Sinks)
 Indoor temperature
 Indoor humidity
 Age of indoor structure
 Type of foundation soil

18. Steps for Investigating IAQ Problems
 Document employee health complaints.
 Examine floor plans and ventilation system
specifications.
 Analysis of data collected from above steps for SBS
score calculations.
 Study of building layout, position and location of
windows, doors, vents, openings etc.
 Ventilation measurement.
 Monitoring of indoor pollutants and other
environmental parameters and development of IAQ
model.
 Develop a plan for reducing and eliminating the IAQ
problem.

19. What is Ventilation??
A process, whereby air is supplied and removed from an indoor
space by natural or mechanical means.
Why ventilation is needed indoors?
To remove heat or moisture OR to reduce the concentration of
one OR more indoor pollutants
Types of Ventilation
•Natural
•Mechanical

20. Natural Ventilation Involves
Infiltration: random/ intentional flow of outdoor air through
windows, cracks and a variety of openings in the buildings.
Exfiltration: movement of air from indoor spaces to outdoor.
Limitation of Natural Ventilation
•Fairly inefficient as it is NOT UNIFORMLY distributed. Air doesn’t circulate
evenly and stale air gets collected in some dead end spaces.
•It brings POLLENS & OTHER POLLUTANTS from outside air.
•Maximum energy loss occurs as NO CONSERVATION of energy can be done.

21. Mechanical ventilation
It involves use of fans and heating / air conditioning equipments.
Principle of mechanical ventilation
•Pulling fresh air from outside to indoor spaces.
•Exhaust stale air.
•Control temperature and humidity inside.

22. Air Flow Inside the Buildings
Stagnation zone
Air in
Air out
Air flow, when uniform mixing
inside (mechanical ventilation)
Air flow pattern, when natural
ventilation occurs

23. Ventilation Measurement
A. In naturally ventilated buildings
• By Infiltration measurement.Infiltration is reported as air change per hour
(ACH) – the average rate at which indoor air is replaced by fresh outdoor air.ACH
is a rough guideline for different building conditions, given by ASHRAE. For e.g.,
in “air tight buildings” ACH is 0.1 to 0.2, in “leaky building”, ACH is 2.0 to 3.0.
ASHRAE model for measuring infiltration in naturally ventilated buildings is –
I = ln (CO / Ci) / t
• Tracer gas technique is employed to measure infiltration. Non reactive gases,
e.g. SF6/NO are used as tracer gases with the assumption that the loss of tracer gas
is only due to ventilation/ exfiltration.
B. In mechanically ventilated buildings
• ACH is measured by CO2 concentration. It is a good surrogate index to determine
the proper ventilation in HVAC buildings. ASHRAE model for measuring
infiltration in HVAC buildings is –
Q = G/ Ci – Ca
Minimumrecommended ventilation rate by ASHRAE is 8L/sec. per person to maintain
the indoor concentration of CO2 as 700 ppm.

24. Parameters for Natural Ventilation
Air Flow- occurs mainly due to two driving forces
1. Pressure Gradient – Difference in outdoor and indoor pressure
(varies with building shape, size, openings, wind direction, local
environmental densities, neighbour building’s configuration,
topography etc.)
2. Temperature Gradient (Buoyancy Forces)- when the inside air
temperature is higher than outside air, the warm air at floor
surface starts rising and the cool air starts entering as a
result of vaccum created at floor surface. This effect is called as “Stack
Effect”.

25. Parameters for Mechanical Ventilation
Infiltration air
Exfiltration air
Recirculated air
Exhaust air
Makeup air

26. What is sick building syndrome?
The feeling of illness among majority of occupants of a conditioned
space is called “Sick Building Syndrome”. A variety of illness
symptoms reported by occupants in sick buildings are –
Headache, fatigue, irritation in eyes, nose and throat, shortness of
breathe etc.
Causes
Inadequate ventilation – insufficient supply of outside air; poor mixing;
fluctuations in temperature & humidity; air filtration problem due to lack of
maintenance of HVAC systems.
The CO2 level indicates the ventilation efficiency of buildings. Building
shows SBS symptoms, if CO2 concentration > 1000 ppm.