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Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
Page 82 The Australian Journal of Construction Economics & Building
COMBATING THE ‘SICK BUILDING SYNDROME’
BY IMPROVING INDOOR AIR QUALITY
Pongchai Nimcharoenwon and Graham Miller, School of Construction, Property
And Planning, University of Western Sydney, New South Wales, Australia
1. Introduction
1.1 Sick Building Syndrome (SBS)
The Sick Building Syndrome (SBS) is a
term often used to explain symptoms,
such as headaches, dizziness, runny
noses, itchiness and so on, produced by
any harmful environment in buildings,
especially in air-conditioned buildings
(Royal Australian Institute of Architects,
1991, p.1). As approximately 80 to 90%
of people’s time is spent in buildings
(EAP, 1998,), concerns about indoor air
quality resulting in such symptoms are
increasing.
There are a number of methods
which appear to be able to reduce the
SBS symptoms, such as
purifying/cleaning indoor air and utilising
materials for construction, furniture and
finishes that have been proven to reduce
adverse effects. O’Brian (1988) and
Karnstedt (1991), suggest that ionised air
is beneficial to human health and can also
reduce the symptoms of SBS.
Based on the premise that, if SBS
and the potential for harmful conditions
within buildings are to be avoided, building
professionals require suitable design tools
(Ferguson 1987, p.1), this paper describes
a method for estimating how much
additional negative ions should be added
to a room/office to compensate for the
losses caused by three major factors
namely, video display terminals (VDT),
heating ventilation and air-conditioning
(HVAC) and building contents (BC).
1.2 Negative Ions
Ions are electrically charged atoms or
molecules that can gain or lose an
electron (Bionic Products, 1998). An atom
gaining electron(s) is called a negative ion
and an atom losing electron(s) are called
a positive ion. From this formation process
of the ions, there seem to be a number of
ion effects, positively and negatively in
terms of indoor air quality.
With regard to the nature of the
movement of electrons, negative ions
(atoms with excess electrons) are quicker
than positive ions. The positive effects of
this phenomenon can be felt near
waterfalls, in pine forests and on the
seashore where waves are breaking on
the shore (Bionic Products, 1998).
Most negative ions are likely to be
the negative hydrogen ions (-H) produced
by solar continuous spectrum (Massey,
1976, p.673). Massey suggests that the
number of negative ions of carbon (-C)
and oxygen (-O) produced by ozone
reaction are significant. These types of
negative ions are therefore also
considered for the purposes of the
calculations used in this study.
1.3 Negative Ion Therapy
There has been a considerable amount of
research that has shown positive and
beneficial effects from negative ions such
as removing air particles and
contaminants, and preventing and
reducing the SBS (O’Brian, 1988, and
Karnstedt, 1991). Some researchers
however, are sceptical about the positive
effects. They suggest that the reverse
may be true and that generating negative
ions might emit ozone excess that can
irritate eyes and affect the lungs (Nava,
1998). It is not the aim of this study to
argue either way but rather to
demonstrate a method for estimating the
de-ionising effects of key factors in
modern buildings.
The following tables show the possible
effects of the amount of negative ions in
particular areas (Penex Air Ionisers,
1988).
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
The Australian Journal of Construction Economics & Building Page 83
Table 1.1: Possible Effects of Negative Ion Density
Density (ions/cc) Effects
0-100 Dead air, oppressive, difficulty of concentration; virus's and
germs flourish.
500-1000 Normal air found indoors where pollution is low and the building
has open windows.
1000-5000 Country fresh air, the minimum level one should sleep, work
and live in.
5000 + Exceptionally fresh, clean and invigorating air, "mountain air."
50,000 + Pure air, very stimulating, exhilarating and relaxing, germs
cannot live in this air.
Table 1.2: Negative Ion Densities in Places or Conditions
Density (ions/cc) Places or Conditions
0-250 Hermetically sealed steel-structure office building, with central
heating/Air conditioning
20-251 Inside and Airplane
0-100 Smoky indoor air
250-500 Normal indoor air (windows open)
250-750 Urban Air in average industrial city
1,000-2,000 Country Air
1,000-5,000 Mountain Air
5,000-20,000 Inside Caves
25,000-100,000 Waterfalls
2. NEGATIVE ION LOSS IN AIR-
CONDITIONED BUILDINGS
2.1 Factors Decreasing Negative Ions
Negative ions in air-conditioned buildings
may be reduced by a number of means. In
air-conditioned offices principal reducers
of negative ions are, Video Display
Terminals (VDT’s), HVAC (particularly air-
conditioning systems), and Building
Contents (BC’s) including building
materials, furniture and finishes used.
Figure 1 shows the effects of the three
factors reducing negative ions.
As can be seen from the figure 1, each
factor reduces the amount of negative
ions in buildings differently. VDT’s,
appears to decrease negative ions by
emitting ionising radiation as low energy x-
ray. HVAC is likely to reduce the negative
ion density (ions/cc) in air through its
process, especially the process of the air-
conditioning system. The Building
Contents (BC’s), which naturally have
electrostatics, may be electrically
activated by contact, such as sliding and
rolling of two insulating materials. The
electrical charges generated appear to
attract the positive and negative ions in
indoor air and stick on the BC’s surfaces,
and therefore the ions in buildings are
likely to be reduced.
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
Page 84 The Australian Journal of Construction Economics & Building
2.2 How much Each Factor Reduces
Negative Ions
2.2.1 Video Display Terminals (VDT’s)
Studies of VDT’s by the Australian
Radiation Laboratory, (1998), indicate that
the while terminals emit visible radiation,
in creating the image, many types of the
electromagnetic radiation are also
generated, in particular, Extremely Low
Frequency radiation (ELF), and low
energy x-ray. The latter is an ionising
radiation, which can knock electrons out of
negative ions by overcoming the electron
binding energy or electron affinity (EBE) of
negative ions (Australian Radiation
Laboratory, 1998, Ionising Radiation
Quantities And Unit). The negative ions
then lose their potential (see also figure
2).
As a consequence of this, the energy of
low energy x-ray and the electron binding
energy or electron affinity of negative ions
(EBE) can be calculated and consequently
the amount of negative ions eliminated
can also be calculated.
The following equation indicates the
relationship of participant parameters for
estimating Negative Ion Loss from VDT’s
(VDT-NIL).
VDT-NIL α LEX, 1/EBE, Rr, and Fn
(Equation 1)
Where:
LEX = Low Energy X-ray = approx.9 to 20
keV per a VDT (ARL, 1998, Calibration:
Therapy Dosimeter Radiation Qualities)
EBE = Electron Binding Energy of -H and -
O2 = approx.0.277 and 0.440 eV (Massey
H., 1976, p.9 and 184)
HVAC
Building
Contents (BC)
VDT’s
- reduce the density of
negative ions flowing in
Air Ions
- reduce negative ions by
attracting to BC’s surfaces
Building
- eliminate negative
ions by ionising
radiation
Figure 1: Three main factors affecting negative ion decrease in buildings
-
-
ion
+
-
-
-
+
+
ion-surface
electron
EBE
x-ray from VDT knocking
an electron out of the atom
Figure 2: the typical positions of electrons in an ion
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
The Australian Journal of Construction Economics & Building Page 85
Rr = Refresh rate of VDT’s = approx.50 to
95 Hz (Tijierina L., 1984, p.7)
Fn = Negative Ion Factor = approx.4/9
(ration between ordinarily positive and
negative ions)
From the relationship in Equation (1), the
Negative Ion Loss (NIL) by VDT’s can be
estimated in terms of the negative ions
reduced in a period of operating time as
follows:
VDT-NIL = 4.7 x Nv x PO +-15% bil.
ions (Equation 2)
Where:
Nv = Number of the VDT’s
PO = Period of Operating the VDT’s
This above Equation (2) shows the loss of
negative ions by the low energy x-ray of a
VDT. Moreover, it determines by referring
to the possible effect of the loss, to the
lowest electron binding energy of negative
ions. As an example two normal 14” or 15”
television and computer screens might
eliminate almost all the negative ions
(typically 500 neg.ions/cu.cm) in a closed
room of 3 x 3 x 2.4 m within 30 mins.
2.2.2 HVAC
The Negative Ion Loss from HVAC
(HVAC-NIL) can be calculated from the
fact that particles in air are likely to be
electrically charged by an electric field
intensity (about 30 kV/cm) in any normal
condition including air-conditioned
buildings (Hendricks, cited in Moore,
1973, p.57). They then attract the opposite
charge of ionised air (negative or positive
charge), and thus a number of negative
ions will stick their electrons on the
particle surfaces (see also figure 4). Each
negative ion is assumed to have an
excess electron of approximate 1.6 x 10^-
19 C (Weisstein, 1996)
After the air conditioning system
filters a number of the atmospheric dust
and/or particles, a number of negative
ions seem to be also obstructed by
filtering. The process is to consider
filtering atmospheric particles, and
assume the particles as spheres. The
electric field intensity can be considered
as an average value, which includes the
intensity of the air conditioning system and
others (Hendricks, cited in Moore, 1973,
p.57)
The Negative Ion Loss (HVAC-NIL) is
estimated as a percentage of the
difference between negative ions outside
and inside (%NIL). The following equation
shows the relationship of the participant
parameters for this.
%NIL α Qp, rp, Fn, Dneg, 1/Cp, Fh, %Ef,
and 1/Dp (Equation 3)
Where:
Qp = Charge of a particle = 3.1 x 10^-4 x
R^2 (Hendricks, cited in Moore, 1973,
p.59)
++
++
-
-
+
-
+
-
-
+
+
+
+
+
-
-
Figure 4: Cross section showing negative ions attracting a particle
Negative
ion
Particle and
Electric charges
-
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
Page 86 The Australian Journal of Construction Economics & Building
rp = Radius of a particle
Fn = Negative Ion Factor = approx.4/9
(ration between ordinarily positive and
negative ions)
Dneg = Density of negative ions outside
(ions/cc)
Cp = Particle concentration (gm/cu.m)
Fh = HVAC flow rate (cc/s)
%Ef = Filtration efficiency of HVAC (air
conditioning systems)
Dp = Density of particles (particles/gm)
From the relationship (equation 3), the
percentage of negative ions reduced
(%NIL) in any area type (or in any particle
concentration) can evaluated as shown in
figure 5. The parameters assumed are
that the flow rate of the air conditioning
system (Fh), and negative ions density
outside (Dneg) are 200 CFM and 200 to
1000 ions/cc, respectively. For example,
in urban air the density (ions/cc) of indoor
negative ions is approximately 150
ions/cc.
2.2.3 Building Contents (BC)
This section illustrates the effects of
electrostatics on the BC’s surfaces such
as building materials and furniture. The
effect seems to come from normal
activities of the occupants in buildings,
such as sitting on a chair, documents
being put on a table, walking on a floor,
and so on (Electro Statics, 1998). Such
activities may potentially bring about
electrically charged surfaces. The
electrically charged ions (negative and
positive ions) in the indoor air will be
attracted (polarised) by the charged
surfaces and eventually be reduced in the
air.
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
2.00E-05
4.00E-05
6.00E-05
8.00E-05
1.00E-04
2.00E-04
4.00E-04
6.00E-04
8.00E-04
1.00E-03
2.00E-03
Particle Concentration (gr/cu.m )
Percentage of Negative Ions between Inside
and Outside
% NIL, 1000 Dneg
% NIL, 200 Dneg
rural
urban
‘When two insulating materials are rubbed
together, the surfaces acquire a net
electric charge, with one becoming
negative and the other positive.’ (Cross,
1987, p.17). This is the action of the
electrostatic potential on the material
surfaces. In addition, the action is likely to
be caused by contact between two
materials. The unbalancing charges, after
that, occur at the material surfaces and
become polarising. Effectively, air ions will
be attracted by the opposite charged
surface and give up their potential (Jowett,
1976, p.56). Figure 6 shows the simply
contacting action of two materials during
and after contacting.
Figure 5: Relationship between %NIL and Particle Concentrations
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
The Australian Journal of Construction Economics & Building Page 87
From the effective contacting of two
insulators (see also figure 6), the
relationship between the negative ions
attracted by the positive charges and
related parameters can be demonstrated
as follows:
BC-NIL α σ, %σ,max., and 1/Rσ,m/i
(Equation 4)
Where:
σ = ideal surface charge density of two
materials = approx.1.656 x 10^10 e/sq.cm
(Jowett, 1976, p.116)
%σ,max = the maximum percentage of
sliding and rolling contacts = approx.8%
(Jowett, 1976, p.116)
Rσ,m/i = Ratio between the surface
charge density of metal and insulate
materials = approx.10,000 to 26,000
As a consequence of this, while the
material surfaces are electrostatically
activated and become electrical charge,
negative and positive ions seem to be
attracted by polarisation of the opposite
surface charges of about 5.095 x 10^4 to
1.325 x 10^5 e/sq.cm. Equation (5) is a
formula to estimating Negative Ion Loss
from the Building Contents (BC).
BC-NIL = max.1.325 x 10^9 x NoCT x
Abc ions (Equation 5)
Where:
NoCT = Number of effective Contacts
Abc = surface Area of Building Contents
contacted
An example of this is in an office building
where the contents, the seat(s) of chairs
used, computer keyboard(s) used and so
on, may affect the Static Electrification. If
we assume their areas to be about 5
sq.m, this room will lose approximately a
maximum of 6.63 bil.ions of negative ions.
3. NEGATIVE ION LOSS TESTING
3.1 DOF-NIL Formula
Three Negative Ion Loss formulas can be
incorporated and become DOF-NIL
formula. The relationship between the
DOF-NIL and participant parameters is
demonstrated in the following equation.
DOF-NIL α Nv, PO, AT, FR, NoCT, and
Abc (Equation 6)
Where:
Nv = Number of VDT’s
PO = Period of Operating time of VDT and
HVAC
AT = Area Type (urban or rural)
FR = air Filtration Rate of HVAC (air-
conditioning system)
FE = Filtration Efficiency of HVAC (air-
conditioning system)
NoCT = Number of effective Contacts of
two insulate materials
Abc = surface Area of a Building Content
contacted
3.2 Testing Negative Ion Loss In Air-
conditioned Offices
To validate the results provided by the
formula, testing of Negative Ion Loss (NIL)
was performed using an instrument called
an Air Ion Counter (AIC). The test was
2
a contact
a balancing
charge
Surface charged during contracting
1
2
negative ions
attracted
a negative charge
------------
+ + + + +
a positive charge
After contacting
Figure 6: Electric charge surfaces of two building materials
1
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
Page 88 The Australian Journal of Construction Economics & Building
performed in two different areas: a typical
air-conditioned office (3m x 3m x 2.4mH),
and a room (6m x 3m x 2.4mH), which
was used for testing only the effects of an
air conditioning system, and the density of
negative ions outside the rooms (Dneg) -
about 1,500 ions/cc.
DOF-NIL showed the results in terms of
negative ion density (ions/cc) in the
rooms, and the rate (ions/hr) of negative
ions reduced by VDT’s and BC’s with +-
15% error of VDT and BC effects. The AIC
showed the negative-ion density (ions/cc)
in each room with 25% accuracy.
The results were as follows:
In the air-conditioned office and the
control room, the negative ion densities
inside were about 1,400 and 1,450
ions/cc with the negative ion decrease
rates of about 1x 10^10 and 1 x 10^9
ions/hr, whereas the AIC showed the
density of about 600 and 1,250 ions/cc,
respectively.
Figure 7 below, shows the rates of
additional negative-ions required for the
condition of 1,500 ions/cc in the required
period of 1 to 10 hours. The additional rate
indicated by the AIC drops sharply when
longer ion-generation is required.
Whereas according to the DOF-NIL
formula the rate remains quite stable over
any time period. However the estimated
required rate of additional negative-ions
for a 3 to 4 hour period (a realistic time
period) as calculated using the DOF-NIL
formula compared favourably with results
obtained by the Air Ion Counter (AIC) - for
an air-conditioned office this is
approximately 12 billion ions/hr.
Figure 7.1: Typical Office
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.25
1
3
5
7
9
Time required (hr.
)
AIC; 25% accuracy
DOF-NIL; 30% erro
r
Figure 7.2 A room and only
air conditioning system
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
0.25
1
3
5
7
9
Time required (hr.
)
AIC; 25% accuracy
DOF-NIL; 30% erro
r
4. CONCLUSIONS
It is proposed that the DOF-NIL formula
described provides a method that has a
reasonable degree of accuracy for
estimating the amount of negative ion loss
in air-conditioned buildings for the critical
3 to 4 hour period. The DOF-NIL formula
can be used to estimate the loss in terms
of negative ion density (ions/cc) by HVAC,
and the rate (ions/hr) of negative ions
reduced by VDT’s and BC’s. A weakness
with the DOF-NIL formula, is that only
considers three factors, whereas a
suitable instrument can take account of
significantly more factors, for example the
effects of air leakages in buildings and the
effect of particle size and density.
However these factors and the additional
factors measured by an instrument appear
Figure 7: Additional Negative-Ions for 1 to 10 hours required
Combating the ‘Sick Building Syndrome’ by Improving Indoor Air Quality by Pongchai Nimcharoewon and Graham Miller
The Australian Journal of Construction Economics & Building Page 89
to be relatively minor in their effect, and
the difference in the results obtained are
therefore also minor. Currently available
instruments require a considerable
amount of time to record data – typically
up to 10 hours and require a real building
to obtain results, whereas applying the
formula method can produce data quickly
and easily which can be used at the
design stage to avoid possibly costly
mistakes and/or to introduce measures to
counter the adverse effects of
deionisation.
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(1998), Calibration: Therapy Dosemeter
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Unit, http://www.
health.gov.au:80/arl/irs_bg2_htm (10
September, 1998)
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http://www.health.gov.au:80/arl/is_vdtrd.ht
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October, 1998)
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http://www.pentex.com/homepage. html (9
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Ions Can Do Strange Things To You,
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gain.com/electrocorp/strange.html (23
August, 1998)
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