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BEAM P
LUS FOR
E
XISTING
B
UILDINGS
I
NDOOR
E
NVIRONMENTAL
Q
UALITY
(I
EQ
)
V
ERSION
1.2
Copyright © 2012 BEAM Society Limited. All rights reserved.
Page 105
B
ACKGROUND
Post-SARS, a lot more attention has been paid to building hygiene.
Clearly, certain features of building and building services design, e.g.
plumbing and drainage systems, are likely to contribute to health
problems. Proper provisions for inspection, cleaning and maintenance
allows for comprehensive management of hygiene in buildings.
6.3 I
NDOOR
A
IR
Q
UALITY
I
EQ
6 C
ONSTRUCTION
IAQ M
ANAGEMENT
I
EQ
7 O
UTDOOR
S
OURCES OF
A
IR
P
OLLUTION
I
EQ
8 I
NDOOR
S
OURCES OF
A
IR
P
OLLUTION
I
EQ
9 IAQ
IN
C
AR
P
ARKS
B
ACKGROUND
Indoor air quality (IAQ) is defined by a list of the constituents, in both
solid and gaseous states, in air. Subjectively, IAQ is the human
perceived response to nasal irritants in the air. ASHRAE [ 5] defines
‘Acceptable Indoor Air Quality’ as “air in which there are no known
contaminants at harmful concentrations as determined by cognizant
authorities and with which a substantial majority (80% or more) of the
people exposed do not express dissatisfaction.”
A key factor in determining appropriate standards for IAQ is the duration
of exposure. Exposure to indoor pollutants for a matter of minutes (e.g.
car parks), hours (e.g. entertainment establishments), or over a working
day (e.g. offices, classrooms, etc) will be different for most parameters
depending on dose and response. For example, limits of the exposure
considered acceptable for the general public, including the young and
infirm, are different from exposures considered acceptable for the
sedentary workplace, and certainly, the industrial workplace.
Sources of indoor pollutants include outdoor pollutants, building fabric
materials, interior finishes, building systems and equipment, appliances,
consumer products, and the occupants and their activities. The selection
of building materials is important, as pollutants can be emitted for weeks,
months or even years after installation. Air intakes should be sited away
from pollutant sources and avoid short-circuiting with exhausts.
Ventilation system design should not introduce pollutants, and filtering
should be effective in removing outdoor pollutants.
6.4 V
ENTILATION
I
EQ
10 I
NCREASED
V
ENTILATION
I
EQ
11 B
ACKGROUND
V
ENTILATION
I
EQ
12 L
OCALISED
V
ENTILATION
I
EQ
13 V
ENTILATION IN
C
OMMON
A
REAS
B
ACKGROUND
The outside air ventilation to a centrally air-conditioned building should
be adequate for the intended levels of occupancy. The criteria often used
to indicate satisfactory provision of ventilation in occupied premises is
the level of carbon dioxide (CO
2
) at design occupancy. In Hong Kong it is
usual that the minimum values for ventilation rates for various spaces will
be specified in accordance with an appropriate version of ASHRAE 62
[5],or an equivalent design standard. However, the amount of ventilation
supply reaching the breathing zone of occupants is critical to the
adequacy of the ventilation. Inadequate distribution within zones or within
rooms can result in dissatisfaction at a local level, even if the total
ventilation supplied to a space meets specification. It is not possible to
use CO
2
as a measure of satisfactory performance in unoccupied
premises but it is possible to determine if ventilation will be satisfactory
5
American Society of Heating, Refrigeration and Air-conditioning Engineers. ASHRAE 62.1-2007: Ventilation for Acceptable
Indoor Air Quality. Atlanta 2007.