making sure all fuel-burning appliances in the
home are working properly. The growth of mold
can be discouraged by keeping humidity below
50%. Old air filters can themselves be a source of
odor and pollution. Replacing the air filters in an air
conditioning system regularly keeps appliances
working properly and indoor air quality is
improved. Activities like smoking and painting
should be done outside. Many people are surprised
to learn that candles are a large source of particulate
matter indoors. Cleaning is another way to minimize indoor air pollution. Dust can pull SVOCs
from solid materials and release them to the air,
thus introducing pollutants to the air that would
otherwise have remained in the material. It is crucial that the cleaning agent used is perfume free, as
it otherwise functions as a pollution source itself.
Limonene and a-pinene are VOCs often found in
household cleaning products, giving lemony and
piney scents, respectively [21]. These and other
aromatic compounds used as scents can undergo
reactions with ozone yielding oxidation products
harmful to humans, thus contributing to ultrafine
particles in the indoor environment. Humans also
act as sinks by inhaling the polluted air, leading to
deposition of pollutants in our tissue. Deposition
can also occur onto skin, thus introducing pollutants directly to the bloodstream. When pollutants
enter the human body, they can cause adverse
health effects such as eye and airway irritation,
respiratory diseases [22], cardiovascular diseases
[23], and cancer.
Ventilation Systems in Buildings
As mentioned earlier, humans spend most of their
time indoors, thus mainly breathing indoor air.
Hence, heating, ventilation, and air conditioning
(HVAC) systems have been developed to
recirculate air inside buildings, to provide acceptable IAQ and thermal comfort. Ventilation is
defined as the “process of exchanging or replacing
air in any space to provide high indoor air quality
which involves temperature control, oxygen
replenishment, and removal of moisture, odors,
smoke, heat, dust, airborne bacteria, carbon
dioxide, and other gases.” [24]. The main purpose
of ventilation is to dilute indoor air pollutants and
to eventually get rid of them by filtration or by
releasing them outdoors. It can be achieved in two
general ways: mechanical or natural.
Mechanical ventilation relies on fans to drive
ventilation. Mechanical ventilation relies on air
handling units (AHUs) that supply outdoor air
into a building and can also provide filtration,
dehumidification, and conditioning of the supply
air. Natural ventilation is driven by pressure differences that occur naturally in and around buildings.
The total driving pressure depends on the wind
speed and direction, the temperature difference
between zones (e.g., the interior and exterior),
and the difference in height between inlets and
outlets. Natural ventilation takes advantage of
fluid behavior to channel the air through openings
in the buildings [25, 26]. Natural ventilation is a
cheap and efficient option, provided the ambient
air is clean and free of pollution. However, it is not
always suitable due to local climatic conditions for
instance in very humid, cold, or hot environments.
Natural ventilation can be difficult to control, since
it depends on natural driving forces. Mechanical
ventilation techniques enable the construction of
airtight buildings with integrated climate control
units (CCU), which reduce the cost of temperature
control. Mechanical ventilation can be controlled
and monitored, but power or other types of failure
can compromise its functionality. In contrast, natural ventilation systems are passive and efficient in
supplying un-conditioned outdoor air. They have
no need for maintenance and use no energy to drive
ventilation. However, they can be difficult to control and the supply air is un-conditioned. In periods
with cold outdoor temperatures, occupants may
experience low indoor temperatures and draught.
Control can be improved by adding a control system and fitting actuators to shutters, dampers, and
windows; however, the system will then no longer
be passive or entirely maintenance-free and would
be properly classified as a hybrid system, i.e., one
that employs both natural and mechanical elements
[25–27]. Many people like to control the environment themselves by controlling windows and
shades.
Indoor Air Quality: Status and Standards
141
home are working properly. The growth of mold
can be discouraged by keeping humidity below
50%. Old air filters can themselves be a source of
odor and pollution. Replacing the air filters in an air
conditioning system regularly keeps appliances
working properly and indoor air quality is
improved. Activities like smoking and painting
should be done outside. Many people are surprised
to learn that candles are a large source of particulate
matter indoors. Cleaning is another way to minimize indoor air pollution. Dust can pull SVOCs
from solid materials and release them to the air,
thus introducing pollutants to the air that would
otherwise have remained in the material. It is crucial that the cleaning agent used is perfume free, as
it otherwise functions as a pollution source itself.
Limonene and a-pinene are VOCs often found in
household cleaning products, giving lemony and
piney scents, respectively [21]. These and other
aromatic compounds used as scents can undergo
reactions with ozone yielding oxidation products
harmful to humans, thus contributing to ultrafine
particles in the indoor environment. Humans also
act as sinks by inhaling the polluted air, leading to
deposition of pollutants in our tissue. Deposition
can also occur onto skin, thus introducing pollutants directly to the bloodstream. When pollutants
enter the human body, they can cause adverse
health effects such as eye and airway irritation,
respiratory diseases [22], cardiovascular diseases
[23], and cancer.
Ventilation Systems in Buildings
As mentioned earlier, humans spend most of their
time indoors, thus mainly breathing indoor air.
Hence, heating, ventilation, and air conditioning
(HVAC) systems have been developed to
recirculate air inside buildings, to provide acceptable IAQ and thermal comfort. Ventilation is
defined as the “process of exchanging or replacing
air in any space to provide high indoor air quality
which involves temperature control, oxygen
replenishment, and removal of moisture, odors,
smoke, heat, dust, airborne bacteria, carbon
dioxide, and other gases.” [24]. The main purpose
of ventilation is to dilute indoor air pollutants and
to eventually get rid of them by filtration or by
releasing them outdoors. It can be achieved in two
general ways: mechanical or natural.
Mechanical ventilation relies on fans to drive
ventilation. Mechanical ventilation relies on air
handling units (AHUs) that supply outdoor air
into a building and can also provide filtration,
dehumidification, and conditioning of the supply
air. Natural ventilation is driven by pressure differences that occur naturally in and around buildings.
The total driving pressure depends on the wind
speed and direction, the temperature difference
between zones (e.g., the interior and exterior),
and the difference in height between inlets and
outlets. Natural ventilation takes advantage of
fluid behavior to channel the air through openings
in the buildings [25, 26]. Natural ventilation is a
cheap and efficient option, provided the ambient
air is clean and free of pollution. However, it is not
always suitable due to local climatic conditions for
instance in very humid, cold, or hot environments.
Natural ventilation can be difficult to control, since
it depends on natural driving forces. Mechanical
ventilation techniques enable the construction of
airtight buildings with integrated climate control
units (CCU), which reduce the cost of temperature
control. Mechanical ventilation can be controlled
and monitored, but power or other types of failure
can compromise its functionality. In contrast, natural ventilation systems are passive and efficient in
supplying un-conditioned outdoor air. They have
no need for maintenance and use no energy to drive
ventilation. However, they can be difficult to control and the supply air is un-conditioned. In periods
with cold outdoor temperatures, occupants may
experience low indoor temperatures and draught.
Control can be improved by adding a control system and fitting actuators to shutters, dampers, and
windows; however, the system will then no longer
be passive or entirely maintenance-free and would
be properly classified as a hybrid system, i.e., one
that employs both natural and mechanical elements
[25–27]. Many people like to control the environment themselves by controlling windows and
shades.
Indoor Air Quality: Status and Standards
141