**CONCENTRATIONS AND SOURCES OF FORMALDEHYDE AND VOLATILE ORGANIC
COMPOUNDS IN FOUR NEW MANUFACTURED HOUSES**

A.T. Hodgson^1^, D. Beal^2^ and S. Chandra^2^

^1^E.O. Lawrence Berkeley National Laboratory, USA

^2^Florida Solar Energy Center, USA

**ABSTRACT**

The concentrations of formaldehyde, individual volatile organic
compounds (VOCs) and total VOCs (TVOC) were measured in four new
manufactured houses on three occasions over nine months following
construction. Ventilation rates were also measured. A mass-balance model
was used to calculate area-specific emission rates of the target
analytes. Formaldehyde concentrations were all less than a guideline
value of 50 ppb. One-half of the 58 target VOCs had median
concentrations at or below 1 ppb. The most abundant VOCs were terpene
hydrocarbons, ethylene glycol, hexanal, 2-butanone and acetic acid.
Concentrations of hexanal, other aldehydes and acetic acid often
exceeded their odor thresholds. The median TVOC concentration was 1.6 mg
m^-3^. In general, there were no large decreases in the emission rates
of individual VOCs or TVOC over the course of the study. The data
suggested that wood products were a dominant source of VOCs in all
houses.

**INTRODUCTION**

Indoor sources of volatile organic compounds (VOCs) and building
ventilation are important determinants of indoor air quality (IAQ) in
houses. Many materials used to construct and finish houses emit VOCs and
some emit formaldehyde. The trend in new house construction is to make
building envelopes tighter. Consequently, ventilation rates are often
relatively low. Elevated sources of indoor contaminants in combination
with low ventilation rates create a potential for degraded IAQ that may
affect occupant health and comfort. Prior to this study, there were no
published VOC data for contemporary manufactured houses in the USA.

The objectives of the study were to: 1) quantify concentrations of total
VOCs (TVOC), individual VOCs, and formaldehyde in four new manufactured
houses over nine months following construction; 2) compare the
concentrations to typical values and to odor thresholds; 3) document
temporal changes in emission rates; and 4) evaluate the effectiveness of
several ventilation and source modifications for reducing concentrations
of VOCs.

**METHODS**

The four, two-section houses were constructed at a single manufacturing
plant in Florida, USA. They were produced and set up at an adjacent
model center during July and August 1997. All houses were equipped with
a heating, ventilating and air conditioning (HVAC) system and a central
occupant-controlled exhaust fan. The HVAC systems were operated daily.
One of the houses had supplemental mechanical ventilation. Material
substitutions were made in several of the houses either during the
manufacturing or set up phases. The houses were decorated and fully
furnished, but unoccupied. Air samples for the analysis of VOCs and
formaldehyde were obtained in September and November 1997 and May 1998.
On each occasion, the samples were collected at a central location in
each house and at a nearby outdoor location. Formaldehyde samples were
collected on cartridges treated with 2,4-dinitrophenylhydrazine. Samples
for TVOC and VOCs were collected on Tenax-TA sorbent tubes. Ventilation
rates were measured concurrently with the collection of air samples by
tracer-gas decay using sulfur hexafluoride as the tracer gas.

Formaldehyde samples were analyzed by high-performance liquid
chromatography following U.S. EPA Method TO-11. Sorbent tubes were
analyzed for TVOC and individual VOCs by thermal desorption gas
chromatography/mass spectrometry (GC/MS) using a modification of U.S.
EPA Method TO-1. For the analysis of TVOC, a GC/MS total-ion-current
chromatogram was integrated over a retention-time range bounded by
n-heptane and\
n-heptadecane. The area response was calibrated with a mixture of ten
common alkane and aromatic hydrocarbons. 58 target VOCs were selected
for analysis. Some of the compounds are indicative of specific indoor
sources. Others have low odor thresholds or are strong sensory
irritants. 42 of the compounds are among the 63 target VOCs recommended
to be included in an analysis of TVOC \[1\]. The concentration data for
the target VOCs were also summarized as ΣVOC (*i.e*., the sum of the
individually measured VOC concentrations).

A steady-state mass-balance model was used to calculate area-specific
emission rates with indoor and outdoor concentrations, ventilation rates
and house volumes and areas as inputs.

**RESULTS**

The house specifications are given in Table 1. House M2 had supplemental
mechanical ventilation provided by an outside air duct connected to the
HVAC return duct and operated intermittently by a FanRecycler control
device \[2\]. Low-VOC paints were used in House M2, and a low-emitting
carpet assembly was installed in Houses M2 and M4.

Table 1. Specifications for the four houses.

+---+-------------------+----------+----------+----------+----------+
|   | > Parameter       | M1       | M2       | M3       | M4       |
+---+-------------------+----------+----------+----------+----------+
|   | > Floor area,     | 112      | 169      | 141      | 131      |
|   | > m^2^            |          |          |          |          |
+---+-------------------+----------+----------+----------+----------+
|   | > Volume, m^3^    | 273      | 412      | 344      | 320      |
+---+-------------------+----------+----------+----------+----------+
|   | > Supplemental    | No       | Yes      | No       | No       |
|   | > vent.           |          |          |          |          |
+---+-------------------+----------+----------+----------+----------+
|   | > Ventilation     | 0.57 -   | 0.53 -   | 0.35 -   | 0.35 -   |
|   | > rate, h^-1^     | 0.78     | 0.71     | 0.36     | 0.50     |
+---+-------------------+----------+----------+----------+----------+
|   | > Carpet area,    | 72       | 128      | 94       | 96       |
|   | > m^2^            |          |          |          |          |
+---+-------------------+----------+----------+----------+----------+
|   | > Sheet vinyl     | 0        | 29       | 29       | 21       |
|   | > area, m^2^      |          |          |          |          |
+---+-------------------+----------+----------+----------+----------+
|   | > Low-VOC paint   | No       | Yes      | No       | No       |
+---+-------------------+----------+----------+----------+----------+
|   | > Low emitting    | No       | Yes      | No       | Yes      |
|   | > carpet          |          |          |          |          |
+---+-------------------+----------+----------+----------+----------+

The concentrations of TVOC and ΣVOC in the four houses are shown in
Figures 1 and 2, respectively. TVOC concentrations ranged from 0.81-3.0
mg m^-3^ with a median value of 1.6 mg m^-3^. TVOC concentrations in
Houses M2 and M4 were relatively constant over time. For House M3 only,
there was a substantial decrease in TVOC concentration from the 1^st^ to
the 2^nd^ sampling period. For House M1, the TVOC concentration in the
final sampling period was distinctly lower than concentrations in the
1^st^ and 2^nd^ periods. ΣVOC concentrations ranged from 44-100% of the
TVOC concentrations. Typically, the individual VOCs accounted for \~70%
of the TVOC values. The median ΣVOC concentration was 1.2 mg m^-3^.

Five target VOCs, n-propylbenzene, isopropyl acetate, trichloroethene,
tetrachoroethene and 1,4-dichlorobenzene, were not detected. 14 target
VOCs had concentrations that were consistently at or below 1 ppb in all
houses and sampling periods. These were benzene, ethylbenzene,
1,3,5-trimethylbenzene, naphthalene, 4-phenylcyclohexene,
n-pentadecane,\
n-hexadecane, propylcyclohexane, butylated hydroxytoluene, methyl
isobutyl ketone,\
1-phenylethanone, ethyl acetate, butyl acetate, and benzothiazole. About
one-half of the target VOCs had median concentrations at or below 1 ppb.
The concentrations (ppb) of 23 selected VOCs are listed in Table 2.
These were either the dominant or most odorous compounds. The
uncertainty for sampling and analysis of most VOCs was about 10%
relative standard deviation. The relative uncertainty for the glycol
ethers and acetic acid was 35% or more. Seven VOCs were among the
most-abundant compounds in all four houses. These were α-pinene,
β-pinene, 3-carene, ethylene glycol, hexanal, 2-butanone, and acetic
acid. ![](media/image1.wmf)Acetic acid was the dominant compound.

The formaldehyde concentrations are shown in Figure 3. The median
formaldehyde concentration was 37 ppb, and all concentrations were less
than 50 ppb.

The ranges of ventilation rates measured in the houses are shown in
Table 1. Houses M1 and M2 had the highest ventilation rates, while House
M3 had consistently lower rates. All of the values meet or exceeded the
ASHRAE minimum ventilation standard of 0.35 h^-1^.

The area-specific emission rates of TVOC are shown in Figure 4. The
median TVOC emission rate was 1.6 mg m^-2^ h^-1^. There was no obvious
trend of TVOC (or ΣVOC) emission rates decreasing with time throughout
the study. However, for Houses M1, M3 and M4, the TVOC emission rate in
the final sampling period was less than the emission rate in the 1^st^
sampling period. The TVOC emission rate in House M2 was constant over
time. In the final sampling period, acetic acid accounted for 44-56% of
the ΣVOC (mg m^-2^ h^-1^) emission rates in the four houses.

There was also no general trend in the temporal profiles of the
area-specific emission rates of the target VOCs. Among the dominant VOCs
reported in Table 2, the emission rates of only\
n-decane, n-undecane, α-pinene, and 2-butanone decreased from the 1^st^
to the final sampling period in all four houses. On the other hand, the
emission rates of 1-octanol, 2-butoxyethanol, nonanal and acetic acid
increased from the 1^st^ to the final sampling period in all houses. The
acetic acid emission rate increased by a factor of two to ten.

Table 2. Concentrations (ppb) of selected individual VOCs in the four
houses on three sampling dates.

<table>
<colgroup>
<col style="width: 16%" />
<col style="width: 11%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
</colgroup>
<tbody>
<tr class="odd">
<td></td>
<td>Chemical</td>
<td colspan="3">M1</td>
<td colspan="3">M2</td>
<td colspan="3">M3</td>
<td colspan="3">M4</td>
<td>Med.*</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Compound</p>
</blockquote></td>
<td>Class</td>
<td>9/97</td>
<td>11/97</td>
<td>5/98</td>
<td>9/97</td>
<td>11/97</td>
<td>5/98</td>
<td>9/97</td>
<td>11/97</td>
<td>5/98</td>
<td>9/97</td>
<td>11/97</td>
<td>5/98</td>
<td>Conc.</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Toluene</p>
</blockquote></td>
<td>AromaticHC</td>
<td>2</td>
<td>3</td>
<td>1</td>
<td>6</td>
<td>3</td>
<td>2</td>
<td>4</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>2</td>
<td>2</td>
</tr>
<tr class="even">
<td><blockquote>
<p>n-Decane</p>
</blockquote></td>
<td>AlkaneHC</td>
<td>16</td>
<td>14</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>&lt;1</td>
<td>8</td>
<td>4</td>
<td>2</td>
<td>2</td>
<td>1</td>
<td>1</td>
<td>1</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>n-Undecane</p>
</blockquote></td>
<td>AlkaneHC</td>
<td>7</td>
<td>7</td>
<td>2</td>
<td>&lt;1</td>
<td>&lt;1</td>
<td>&lt;1</td>
<td>3</td>
<td>2</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>&lt;1</td>
<td>1</td>
</tr>
<tr class="even">
<td><blockquote>
<p>n-Dodecane</p>
</blockquote></td>
<td>AlkaneHC</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>3</td>
<td>2</td>
<td>10</td>
<td>8</td>
<td>6</td>
<td>5</td>
<td>4</td>
<td>3</td>
<td>3</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>n-Tridecane</p>
</blockquote></td>
<td>AlkaneHC</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>6</td>
<td>7</td>
<td>6</td>
<td>21</td>
<td>17</td>
<td>12</td>
<td>12</td>
<td>10</td>
<td>7</td>
<td>7</td>
</tr>
<tr class="even">
<td><blockquote>
<p>n-Tetradecane</p>
</blockquote></td>
<td>AlkaneHC</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>4</td>
<td>4</td>
<td>5</td>
<td>13</td>
<td>10</td>
<td>11</td>
<td>6</td>
<td>6</td>
<td>5</td>
<td>5</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>α-Pinene</p>
</blockquote></td>
<td>TerpeneHC</td>
<td>13</td>
<td>19</td>
<td>5</td>
<td>9</td>
<td>31</td>
<td>10</td>
<td>35</td>
<td>32</td>
<td>15</td>
<td>23</td>
<td>25</td>
<td>9</td>
<td>17</td>
</tr>
<tr class="even">
<td><blockquote>
<p>β-Pinene</p>
</blockquote></td>
<td>TerpeneHC</td>
<td>3</td>
<td>6</td>
<td>2</td>
<td>2</td>
<td>7</td>
<td>3</td>
<td>11</td>
<td>8</td>
<td>5</td>
<td>7</td>
<td>6</td>
<td>3</td>
<td>5</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>3-Carene</p>
</blockquote></td>
<td>TerpeneHC</td>
<td>3</td>
<td>6</td>
<td>2</td>
<td>1</td>
<td>5</td>
<td>2</td>
<td>15</td>
<td>11</td>
<td>7</td>
<td>9</td>
<td>10</td>
<td>4</td>
<td>5</td>
</tr>
<tr class="even">
<td><blockquote>
<p>d-Limonene</p>
</blockquote></td>
<td>TerpeneHC</td>
<td>2</td>
<td>3</td>
<td>1</td>
<td>1</td>
<td>3</td>
<td>2</td>
<td>7</td>
<td>5</td>
<td>4</td>
<td>5</td>
<td>5</td>
<td>3</td>
<td>3</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>1-Butanol</p>
</blockquote></td>
<td>Alcohol</td>
<td>2</td>
<td>6</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>1</td>
<td>4</td>
<td>4</td>
<td>5</td>
<td>3</td>
<td>4</td>
<td>4</td>
<td>4</td>
</tr>
<tr class="even">
<td><blockquote>
<p>1-Octanol</p>
</blockquote></td>
<td>Alcohol</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>1</td>
<td>3</td>
<td>1</td>
<td>1</td>
<td>3</td>
<td>1</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Phenol</p>
</blockquote></td>
<td>Alcohol</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>4</td>
<td>4</td>
<td>4</td>
<td>6</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>3</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Ethylene glycol</p>
</blockquote></td>
<td>Glycol</td>
<td>32</td>
<td>39</td>
<td>12</td>
<td>41</td>
<td>44</td>
<td>17</td>
<td>&lt;11</td>
<td>&lt;10</td>
<td>21</td>
<td>&lt;9</td>
<td>44</td>
<td>21</td>
<td>21</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>1,2-Propanediol</p>
</blockquote></td>
<td>Glycol</td>
<td>&lt;3</td>
<td>12</td>
<td>4</td>
<td>&lt;3</td>
<td>5</td>
<td>&lt;3</td>
<td>&lt;4</td>
<td>&lt;3</td>
<td>&lt;3</td>
<td>&lt;3</td>
<td>4</td>
<td>3</td>
<td>&lt;3</td>
</tr>
<tr class="even">
<td><blockquote>
<p>2-Butoxyethanol</p>
</blockquote></td>
<td>Glycol</td>
<td>1</td>
<td>2</td>
<td>1</td>
<td>3</td>
<td>5</td>
<td>5</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>6</td>
<td>6</td>
<td>3</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Hexanal</p>
</blockquote></td>
<td>Aldehyde</td>
<td>8</td>
<td>20</td>
<td>8</td>
<td>10</td>
<td>19</td>
<td>12</td>
<td>26</td>
<td>22</td>
<td>17</td>
<td>25</td>
<td>25</td>
<td>16</td>
<td>18</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Heptanal</p>
</blockquote></td>
<td>Aldehyde</td>
<td>1</td>
<td>2</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Octanal</p>
</blockquote></td>
<td>Aldehyde</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>3</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Nonanal</p>
</blockquote></td>
<td>Aldehyde</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>3</td>
<td>4</td>
<td>4</td>
<td>3</td>
<td>4</td>
<td>3</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>2-Butanone</p>
</blockquote></td>
<td>Ketone</td>
<td>6</td>
<td>8</td>
<td>2</td>
<td>16</td>
<td>28</td>
<td>6</td>
<td>7</td>
<td>4</td>
<td>4</td>
<td>8</td>
<td>7</td>
<td>5</td>
<td>6</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Acetic acid</p>
</blockquote></td>
<td>Acid</td>
<td>25</td>
<td>102</td>
<td>142</td>
<td>80</td>
<td>122</td>
<td>264</td>
<td>123</td>
<td>120</td>
<td>267</td>
<td>53</td>
<td>126</td>
<td>275</td>
<td>122</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Texanol</p>
</blockquote></td>
<td>Ester</td>
<td>2</td>
<td>7</td>
<td>3</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>1</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
<td>2</td>
</tr>
</tbody>
</table>

> \*Median Concentration.

![](media/image2.wmf)The area-specific emission rates of formaldehyde
ranged from 24-68 µg m^-2^ h^-1^ with a median value of 41 µg m^-2^
h^-1^. The values for each house varied by less than a factor of two,
and there was no consistent trend with time. The hexanal emission rates
ranged from 45-137 µg m^-2^ h^-1^ with a median value of 85 µg m^-2^
h^-1^. For Houses M1, M2 and M4, the highest hexanal emission rates
occurred in the 2^nd^ sampling period. In the final sampling period, the
rates were in a narrow range of 56-65 µg m^-2^ h^-1^. The formaldehyde
and hexanal emission rates were not correlated with each other (r =
0.54).

**DISCUSSION**

TVOC concentrations in various indoor environments are frequently about
1,000 µg m^-3^, or lower \[3\]. One study of a probability-based sample
of \~200 occupied houses of all ages recorded a median TVOC
concentration of 700 µg m^-3^ \[4\]. The TVOC concentration in House M3
during the 1^st^ sampling period was about four times higher than this
value while the median TVOC concentration in the four houses over the
course of the study was only about twice this value. Supplemental
mechanical ventilation may have contributed to the consistent, and
generally low, TVOC concentrations in House M2.

In the past, formaldehyde concentrations in manufactured houses were
frequently in excess of 100 ppb \[5\]. Guidelines for formaldehyde
concentrations in buildings are now established at relatively low
levels. The formaldehyde concentrations in the four houses were all
lower than the most restrictive guideline in the USA of 50 ppb \[6\].
The low formaldehyde concentra-tions are probably due to the exclusive
use of gypsum board panels for walls and ceilings and the relatively low
emissions of formaldehyde from current wood products.

Indoor air concentration data for a number of VOCs have been summarized
from the literature \[3\]. Compounds that had notably elevated
concentrations in the study houses relative to these data included the
alkane and terpene hydrocarbons, n-decane, n-undecane, n-dodecane,\
n-tetradecane, α-pinene and β-pinene. Other compounds in the houses with
elevated concentrations relative to the literature were 1-butanol,
hexanal, nonanal, and 2-butanone.

A number of alcohols, aldehydes and carboxylic acids produce
objectionable odors at low concentration \[7\]. The hexanal
concentrations in the houses frequently were near or exceeded the
hexanal odor threshold of 14 ppb. The odor thresholds for octanal and
nonanal are 1 and 2 ppb, respectively. The concentrations of octanal and
nonanal consistently were at or slightly exceeded these values. The odor
threshold for acetic acid of 140 ppb was approached in all houses during
the 2^nd^ sampling period and was exceeded in all houses during the
final period. Thus, while the concentrations of TVOC and VOCs in the
houses were, in general, not abnormally elevated, it is expected that
some occupants would be able to detect objectionable odors due to
elevated concentrations of aldehydes and acetic acid.

The data suggest that IAQ in the houses was primarily impacted by a few
dominant VOC sources. Phenol and at least a portion of the normal alkane
hydrocarbons, such as n-tridecane and n-tetradecane, may have originated
from the sheet vinyl flooring used only in Houses M2, M3 and M4. Wood
and engineered wood products emit terpene hydrocarbons, such as\
α-pinene, β-pinene and d-limonene. Engineered wood products also emit
hexanal and other aldehydes including heptanal, octanal and nonanal. It
is likely that the terpene hydrocarbons and aldehydes originated from
engineered wood products used in the construction and finishing of the
houses. The possible sources include cabinetry, plywood floor decking
and oriented-strand-board roof decking. The primary source of acetic
acid is uncertain.

The effects of the two source substitution treatments were difficult to
evaluate. House M2 with the low-VOC paints had some of the highest
concentrations of ethylene glycol that is used as a solvent in many
latex paints. It is possible that conventional latex paints were used in
the house during the decorating phase or for touch up. The
concentrations of specific VOCs typically emitted by carpets and carpet
cushions were low in all four houses, suggesting that contemporary
carpet materials are a relatively minor source of VOCs.

**ACKNOWLEDGEMENT**

Sponsored by the U.S. Depart. Of Energy, Assist. Secretary for Energy
Efficiency and Renewable Energy, Office of Building Technology, State
and Community Programs.

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