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Determination of organic compounds in indoor air with potential reference to air quality
DETERMINATION OF ORGANIC COMPOUNDS IN INDOOR AIR WITH POTENTIAL REFERENCE TO AIR QUALITY INGEGERD JOHANSSON Department of Analytical Chemistry, Royal Institute of Technology, P.O. Box, S-100 44 Stockholm 70, Sweden (Firsr received 25 April 1977 and in ~~ul~orm 19 Sepre~r
1977)
Abstract - Concentrations of 15 volatile organic compounds have been investigated in the air of two schoolrooms. The chemical analysis included enrichment on porous polymer beads, heat desorption and gas chromatographic separation on a capillary column connected to either a flame ionization detector or a mass spectrometer. Samples were collected from the indoor air both in the presence and in the absence ofthe pupils (boys and girls, age 16-19) as well as from the ambient outdoor air. The qualitative composition of indoor and outdoor air was found to be about the same: aliphatic and aromatic hydr~ar~ns pr~ominate, though indoors the number of compounds detected is larger and the concentrations are higher. Both the number and the concentration increase in the presence ofhumans. The mean concentrations ofacetone and the sum ofthe concentrations of C,-alkylbenzenes were 7.7 and 8.2pgmT3 respectively in an unoccupied room and increased to 19.8 and 12.1 pgmm3 respectively in an occupied room.
(MS} serve for purposes of identifi~tion (Bergert et al., 1974; Raymond and Guiochon, 1974; Pellizzari et al., 1976b). Many volatile air pollutants have been determined both qualitatively and quantitatively by the use of the analytical systems described above. The main wmpounds have been found to be aliphatic and aromatic hydrocarbons and halocarbons, in the concentration range of a few ppb. Recently, polar compounds have also been detected in urban air (e.g. Pellizzari et al., 1976b). Little attention has been paid to the full composition of indoor air; instead, specific compounds have been determined as for example formaldehyde emanating from chipboard, a construction material (Andersen et al., 1975). One of the few studies dealing with the composition of indoor air has been reported by Dravnieks and Whitfield (1971). They analyzed air in three schools with GC, in combination with test persons’ olfactory analysis of the chromatographi~ effluent. The components separated in the GC were defined only by Kovats Index values (Kovats, 1965). No conclusion about psycho-physical relationships and certainly not about physical-chemical composition of indoor air can be drawn from their results. To facilitate studies of dose-effect relationships of indoor air quality with regard to odours, irritants, and the like, techniques of sampling and analysis must be improved. This report is one part of a series of studies in that direction. The specific aim of the research, reported in the present paper, was to develop a suitable method for sampling, identifying, and quantifying volatile organic compounds in indoor air. The method was tested under field conditions by determining the constituents. of schoolroom air in Stockholm under a number of meters
In buildings like schools, offices, dwellings etc., where the odor criterion usually is critical, no standardized method of measuring the human perception of air quality exists. Usually only the concentration of carbon dioxide is used as a crude indicator of air quality (Pettenkofer, 1885, cited by Friberg and Ronge, 1964). A more fruitful approach to the develop ment of an air quality index would be to consider the amount of volatile organic compounds in the air. However, to date, the composition of these compounds in the indoor air has not yet been completely mapped (Ryd, 1967; Dravnieks and Whitfield, 1971). During the past few years the content of organic compounds in ambient air, on the other hand, has been the subject of many investigations. The analytical systems described involve enrichment of the compounds on sorbent media such as porous polymers (Versino et al., 1974; Russel, 1975), activated charcoals (Grob and Grob, 1971; Raymond and Guiochon, 1974), cold traps (Lonneman et al., 1974), as well as by temperature gradient along sorbing beds (Kaiser, 1973; Bergert et al., 1974). The properties of the different sorbent media, e.g. collection efficiency, recovery and breakthrou~ volumes, have been of interest to only a few researchers (Pellizzari et at., 1976a). Enrichment is followed by desorption of the components by heat into a low-volume cold trap or directly into a gas chromatographic (GC) column. When the cold trap is used a last step is to volatilize the sample into the column for GC analysis. Packed or open tubular columns are used for the GC-separation, usually in conjunction with a flame ionization detector (FID). Electron capture detectors are used for specific compounds and mass spectro-
1371
1372
INGEGERDJOHANSSON
different conditions. It has then been used at this laboratory for several years and works quite well routinely.
EXPERIMENTAL
Sumpiing techniques
The voltaiie organic compounds of the air were enriched in sorbent traps, (Pyrex glass tubes, length 30mm, diameter 12 mm). Porapak Q (a porous polystyrene) was preferred to Tenax GC (porous polymer based on 2,6-diphenyi-p phenylene oxide) as sorbent medium because it has a higher capacity for polar low boiling compounds. Since Tenax GC provides better recovery of less volatile components, it is useful as a complement to Porapak. Before the first use the traps were conditioned by heating at 180°C for 24 h while purging with nitrogen. After each analysis, or after storage for some weeks, they were reconditioned in the same way but only for 2 h. Sampling was performed with a battery operated diaphragm pump. The air flow through the trap was measured by a rotameter and the time of sampling was noted. To avoid contamination from the pump, it was always placed outside the room during sampling. The trap was kept at the ambient temperature to avoid condensation of water. The flow rate was about 1.5 I.min- ’ and sample volumes were t5 1. for FIDanalyses, while MS identification required 10%300 I. The trap was sealed with Teflon stoppers after sampling and brought back to the laboratory. It was connected to the GCcolumn by an eight-port gas sampling valve and heated to 140°C. The components thus desorbed were purged with carrier gas (helium, 12 ml min- ‘) onto the first part (about 1SOmm) of the capillary column which was immersed in liquid nitrogen. In order to avoid plugging of flow by ice derived from water vapour adsorbed in the trap, a first loop of the capillary was supported above the surface of the liquid nitrogen. After 45min the valve was rotated, the cooled part of column heated to 140°C and the compounds were brought into the gas chromatograph. Collection of samples Samples were taken from two schoolrooms (A and B) in two different schools in two different residential city areas of Stockholm. Both schools were centrally heated. No smoking was allowed in the buildings and no other extreme pollutants were present. Room A was ventilated by a self draughting system only and the number of air changes per hour was determined by tracer gas measurements (made by the National Swedish Institute for Building Research). Room B was ventilated by an overflow system including exhaust valves inside the room. The number of air changes per hour was determined here by use of a hot wire anemometer connected to a hood. Air samples were taken from the schoolroom during 10 min periods at the beginning and at the end of a 45 min period either during a class session attended by 1S-20 pupils (16- 19 years old, boys and girls) or in the unoccupied room. Doors and windows were closed all the time and fresh air was supplied by the ventilation system only. For comparison, outdoor air samples were also analysed. To find out whether or not there were any organic sulfur compounds present, the air of Room B - unoccupied and occupied - and the outdoor air were analysed in a GC connected to a flame photometric detector (FPD). The air samples were collected in 1 I. gas burettes. (The analyses were made by SIK - the Swedish Food Institute.) In addition, in Room B, temperature and relative humidity were recorded continuousIy by a thermohygro~aph and the concentration of carbon dioxide was measured every 5 min by infrared s~trophotometry.
W-separation
und detection
The GC column was a wall coated open tubular stainless steel capillary (0.75 mm id. x 145 m) with UCON (a polypropyleneglycol) 50HB 2000 or 5100. It was programmed from 43 to 137°C at a rate of 2”min-‘. starting with an isothermal period of 8 min at 43’C. In the GC-MS analyses the capillary column and a helium make-up gas flow of 20 ml min - ’ were connected to the first stage of the jet-separator of the instrument. The concentrations of 15 compounds were determjned by using their peak heights recorded with the FID. Response factors were obtained by injecting standard aqueous solutions of reference compounds onto a packed column. The carrier gas flow, 12 ml min _ ‘_was the same as in the capillary column. The temperature was adjusted so as to give equal peak widths on both columns. The same calibration curves were used for related compounds.
RESULTS AND DISCUSSION
Figure 1 shows chromatograms. made of 1001. samples taken in (a) the outdoor air, (b) the unoccupied Room A. and (c) the same room during a class session, The volume is larger than the breakthrough volumes for many of the most volatile compounds, for which reason the peaks in the beginning of the chromatograms are about 10”, too small in comparison with the others. Table 1 lists the characterized compounds numbered according to the peaks numbered in the chromatograms. The structure ofeach hydrocarbon isomer has not been determined, and usually only the type of compound is given. Characterizations were based on MS and in some cases also on chromatographic retention. Table 1 shows that the qualitative composition of organic substances in the air is rather similar in all three cases : outdoors, unoccupied and occupied classroom. The aliphatic and aromatic hydrocarbons are predominant, followed by the halocarbons, and a few other compounds, e.g. acetone and ethanol. The number of components detected is larger in indoor than in outdoor air, 160 as compared to 50. Most of them are hydrocarbons; particularly the unsaturated compounds are more numerous indoors. For the quantitative analyses, sample volumes of only 15 I. were taken, so as to aliow proper proportions between the peaks, in light of the fact that the breakthrough volumes could not be reached. The method for quantitation is not very exact. Thus the results are presented as concentration ranges in Fig. 2. In this figure the mean concentration ranges of some components in the air of Room B, as well as in the outdoor air, are shown. The concentrations were always found to be higher indoors than outdoors and to increase when people were present in the room. This is a surprising finding because aliphatic and aromatic hydrocarbons are assumed to originate mainly from industrial and vehicular emissions. The question arrises : are outdoor components, like some hydrocarbons, enriched indoors and a~umulated in the air, or are such compounds simply generated by building
1373
Organic compounds in indoor air
i n
c
Temperature 43
43
50
60
70
80
f”Cf
90
100
110
120
130 137
r
0
I
10
20
30
40
50
Time tmin)
Fig. 1. ~asc~romato~a~ of 100 i. samples taken in (a) the outdoor air, (bf the ~~~u~i~ ~~offlr~orn and (c) the occupied schoolroom. (145 m x 0.75 mm WCON M HB 200DUT, 43°C 8 &a, 2” min- ’ to 137°C; scale on ordinate differs between the chromatograms.) AE:
El
Il.12
3
x
hexane
hexene
58 59
decene
x
x
x
x
x 60
u 4 known dodecane
C4-alkylbenrene c _ _#I_
C3-alkylbenzene
undecene
dadecene
C -alkylbenzene
dlpentene
C -alkylbenzenc
dodecarle undecene
styrene
undecene
dodecane
C?-alkylbenzenc
undecene
dodecane
136)
air
outdoor
Detected
in the. chromatograms.
21
x
(mw
) undecane
undecene
(n-
terpene
undecene
dddecene
C -alkylbenzene
undecene
dodecene
o-xylene
undecene
undecane
L
51
56
55
54
53
52
51
50
49
48
uodecene
undecane
decene
undecene
undecane
decene
undecyne
undecene
m-xylene
Compound
to the peaks numbered
x
heptene
nonene
nonane
heptane
heptene
octene
nonane
nonene
nonane
decane
benzene
oc tene x x
x
octene
heptene
x
x
x
nonane
octene
nonane
ethanol
octene
octane
x x x x x x x x x x ? 1 x x x x x x x x x x x x x x x x x x x x
47
45 46
44
“o
Peak
correspond
20
19
18
17
16
15
14
13
trichloroethane
caibontetrachloride
octane x
x
octane
9
pen tene
x x
x
hexene x
x
heptane
heptene
x
x
heptane
heptane
x
hexene x
x
i soprene
heptane
x x x
hexane
x
classroom
trichlorotrifluoroethane
8
10
n
x
x
i occupied
x
empty classroom
in air. The numbers
trichlorofluaromethane
air
outdoor
Detected
components
hexane
Compound
1. ldentifj~d
ace tone
6
4,s
no
Peak
Table.
x
x
x
x
x
x
x
x
empty classroom
i
n
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
7.
x
x
x
classroom
occupied
Organic compounds in indoor air
x
xx
-*xx
x
xx
*
*xxx
**
xxx
x
xx
1375
*
xx
x*
*
x
*
x
INGEGEFW
JOHANSON
to air quality is of minor importance. In this context it is interesting to note that inside hog farms no reduced organic sulfur compounds have been detected (flame photometry) in spite of the fact that liquid swine manure has an offensive odour (Grennfelt et al., 1977).
Fig. 2. Concentration components in outdoor and air from occupied theses in the figure
ranges [pgrnv3j of a selection of air, airfrom unoccupied schoolroom schoalroom. Numbers within parencorrespond to peak numbers in
~hrom~t~~rarns. materials, ventilation systems inventories, clothes, and humans ? It is obvious from the Fig. 2 that the acetone and ethanol concentrations vary most. They are higher in the uno~upied room than outdoors and increase substantially in the presence of humans (up to an average of24 and 55 c(g rnw3, respectively). One source of these substances is the human breath, which contains an average of 12~~grn-~ of acetone and 240pgm-3 of ethanol at 2O”C, 1 atm (Jansson and Larsson, 1969). With the actuaf air changes and with 0.5 m3 air breathed per person per hour the concentration ranges of acetone and ethanol would be 40_1OOfigm-” and 8%2Ofrgrn-’ respectively. The latter concentration is too low to account for alf of the ethanol measured in our study. Considerable amounts probably originate from perfumes and deodorant sprays. The total concentration of organic compounds were much higher in Room A than in Room B. This may be explained by the different ventifation capacities of the rooms: Room A underwent 0.7 air changes per hour corresponding to about 6 m3 air per person and hour. and Room B underwent 1.8 air changes per hour or about 15 mJ per person and hour. The outdoor concentration of carbon dioxide was 0.03 to 0.04% by volume and the same percentages were obtained in the empty classroom, even after a 45 min period of emptiness. The CO,-concentration did increase during the 45 min period in which pupils were present in the room (to about O.l-0.3%). This increase was correlated to the number of persons present. No organic sulfur compounds or hydrogen sulfide were found, either indoors or outdoors, even though the detection limit of the analytical method was as low as0.1 bigSm-3, This indicates that their contribution
The results of the air analyses show that the qualitative composition of indoor and outdoor air is about the same. Aliphatic and aromatic hydrocarbons predominate, but the number and concentrations of the compounds detected, especially the aliphatic ones, are higher indoors and increase in the presence of humans. Acetone and ethanol vary most and seem to be correlated to humans, and to rooms where humans have been. Carbon dioxide, on the other hand, is only correlated to the number of persons present at the moment, not to the room. Generally, we still know little about interactions between the constituents of the indoor air, as well as between these and the various materials in a room. The room perhaps acts as a “chemical reaction chamber”, for which reason the composition of the indoor air would not be exclusively defined by the composition of the inlet air and the materials in the room. Further investigations are necessary before an accurate description of the indoor air composition can be put forth. Moreover, we must also gain knowledge of the way odorous pollutants are generated and how they behave in rooms.
~~k~#~~ie~~~~n~e~l.s - This work is part of a joint project sponsored by the Swedish Board for Technical Development (proj. no. 75-3299) and by the Swedish Council for Building Research (proj. no. 750117-5, Dr. B. Berglund; proj. no. 750073-7, Dr. T. Lindvall). The author thanks Dr. B. Jansson, National Swedish Environment Protection Board, Professors A. Johansson and F. Ingman, Department of Analytical Chemistry at the Royal Institute of Technology, (Stockholm) for stimulatin~dis~ussions. Drs B. Berglund and T. Lindvall have given valuable comments on the manuscript. REFERENCES
Andersen I., Lundqvist G. R. and M#lhave L. (1975) Indoor air pollution due to chipboard used as a construction material. ~?~~o,~~~e~i~ ~~~~r~n~e~f 9, 1121-i 127. Bergert K.-H. and Betz V. (1974) Erfahrungen bei der quantitativen Analyse von Fliichtigen organ&hen Mikroverunreinigungen in Luft. Chromntographia 7, 681-687. Dravnieks A. and Whjt~eld J. (1971) Gas ~hromatographic study of air quality in schools. ASHRAE Trans. 77, 113.--1x Friberg L. and Ronge H. (1964) ffy@w. Scandinavian University Books, Stockholm. Grennfelt P., Lindvall T., Nor&n O., Rosen C. and Thyselius L. (1977) Odour emission and atmospheric dispersion from hog farms. JTI Report no. 13. Grab K. and Grob G. 11971) Gas-liquid chromatograPbi~-mass s~ctrometric investigation of C,X,, organic compounds in an urban atmosphere. J. ~~r~~a~~~~. 62, l-13.
Organic compounds in indoor air Jansson B. 0. and Larsson B. T. (1969) Analysis of organic compounds in human breath by gas chromatography-mass spectrometry. J. lab. c/in. Med. 74, 961-966. Kaiser R. E. (1973) Enriching volatile compounds by a temperature gradient tube. An&t. Chem. 45, 965-967. Kovats E. (1965) Gas chromatographic characterization of organic substances in the retention index system. Aduan. Chromatogr. 1, 229. Lonneman W. A., Kopczynski S. L., Darley P. E. and Sutterfield F. D. (1974) Hydrocarbon composition of urban air pollution. Environ. Sci. Technol. 8, 229-236. Pellizzari E. D., Bunch J. E., Berkley R. E. and McRae J. (1976a) Collection and analysis of trace organic vapor pollutants in ambient atmospheres. The performance of a Tenax GC cartridge sampler for hazardous vapors. Analyt. Letr. 9, 45-63.
1377
Pellizzari E. D., Bunch J. E., Berkley R. E. and McRae J. (1976b) Determination of trace hazardous organic vapor pollutants in ambient atmospheres by gas chromatography/mass spectrometry/computer. Analyt. Chem. 48, 803-807.
Raymond A. and Guiochon G. (1974) Gas chromatographic analysis of Cs-C,, hydrocarbons in Paris air. Environ. Sci. Tech&. 8, 143-148. Russel J. W. (1975) Analysis of air pollutants using sampling tubes and gas chromatography. Environ. Sci. Technol. 9, 1175-1178. Ryd H. (1967) An attempt to measure objectively the quality of air. The National Swedish Institute for Building Research. Report no. 34:1967. Versino B., de Groot M. and Geiss F. (1974) Air pollution sampling by adsorption columns. Chromatographia 7, 302-304.
1977)
Abstract - Concentrations of 15 volatile organic compounds have been investigated in the air of two schoolrooms. The chemical analysis included enrichment on porous polymer beads, heat desorption and gas chromatographic separation on a capillary column connected to either a flame ionization detector or a mass spectrometer. Samples were collected from the indoor air both in the presence and in the absence ofthe pupils (boys and girls, age 16-19) as well as from the ambient outdoor air. The qualitative composition of indoor and outdoor air was found to be about the same: aliphatic and aromatic hydr~ar~ns pr~ominate, though indoors the number of compounds detected is larger and the concentrations are higher. Both the number and the concentration increase in the presence ofhumans. The mean concentrations ofacetone and the sum ofthe concentrations of C,-alkylbenzenes were 7.7 and 8.2pgmT3 respectively in an unoccupied room and increased to 19.8 and 12.1 pgmm3 respectively in an occupied room.
(MS} serve for purposes of identifi~tion (Bergert et al., 1974; Raymond and Guiochon, 1974; Pellizzari et al., 1976b). Many volatile air pollutants have been determined both qualitatively and quantitatively by the use of the analytical systems described above. The main wmpounds have been found to be aliphatic and aromatic hydrocarbons and halocarbons, in the concentration range of a few ppb. Recently, polar compounds have also been detected in urban air (e.g. Pellizzari et al., 1976b). Little attention has been paid to the full composition of indoor air; instead, specific compounds have been determined as for example formaldehyde emanating from chipboard, a construction material (Andersen et al., 1975). One of the few studies dealing with the composition of indoor air has been reported by Dravnieks and Whitfield (1971). They analyzed air in three schools with GC, in combination with test persons’ olfactory analysis of the chromatographi~ effluent. The components separated in the GC were defined only by Kovats Index values (Kovats, 1965). No conclusion about psycho-physical relationships and certainly not about physical-chemical composition of indoor air can be drawn from their results. To facilitate studies of dose-effect relationships of indoor air quality with regard to odours, irritants, and the like, techniques of sampling and analysis must be improved. This report is one part of a series of studies in that direction. The specific aim of the research, reported in the present paper, was to develop a suitable method for sampling, identifying, and quantifying volatile organic compounds in indoor air. The method was tested under field conditions by determining the constituents. of schoolroom air in Stockholm under a number of meters
In buildings like schools, offices, dwellings etc., where the odor criterion usually is critical, no standardized method of measuring the human perception of air quality exists. Usually only the concentration of carbon dioxide is used as a crude indicator of air quality (Pettenkofer, 1885, cited by Friberg and Ronge, 1964). A more fruitful approach to the develop ment of an air quality index would be to consider the amount of volatile organic compounds in the air. However, to date, the composition of these compounds in the indoor air has not yet been completely mapped (Ryd, 1967; Dravnieks and Whitfield, 1971). During the past few years the content of organic compounds in ambient air, on the other hand, has been the subject of many investigations. The analytical systems described involve enrichment of the compounds on sorbent media such as porous polymers (Versino et al., 1974; Russel, 1975), activated charcoals (Grob and Grob, 1971; Raymond and Guiochon, 1974), cold traps (Lonneman et al., 1974), as well as by temperature gradient along sorbing beds (Kaiser, 1973; Bergert et al., 1974). The properties of the different sorbent media, e.g. collection efficiency, recovery and breakthrou~ volumes, have been of interest to only a few researchers (Pellizzari et at., 1976a). Enrichment is followed by desorption of the components by heat into a low-volume cold trap or directly into a gas chromatographic (GC) column. When the cold trap is used a last step is to volatilize the sample into the column for GC analysis. Packed or open tubular columns are used for the GC-separation, usually in conjunction with a flame ionization detector (FID). Electron capture detectors are used for specific compounds and mass spectro-
1371
1372
INGEGERDJOHANSSON
different conditions. It has then been used at this laboratory for several years and works quite well routinely.
EXPERIMENTAL
Sumpiing techniques
The voltaiie organic compounds of the air were enriched in sorbent traps, (Pyrex glass tubes, length 30mm, diameter 12 mm). Porapak Q (a porous polystyrene) was preferred to Tenax GC (porous polymer based on 2,6-diphenyi-p phenylene oxide) as sorbent medium because it has a higher capacity for polar low boiling compounds. Since Tenax GC provides better recovery of less volatile components, it is useful as a complement to Porapak. Before the first use the traps were conditioned by heating at 180°C for 24 h while purging with nitrogen. After each analysis, or after storage for some weeks, they were reconditioned in the same way but only for 2 h. Sampling was performed with a battery operated diaphragm pump. The air flow through the trap was measured by a rotameter and the time of sampling was noted. To avoid contamination from the pump, it was always placed outside the room during sampling. The trap was kept at the ambient temperature to avoid condensation of water. The flow rate was about 1.5 I.min- ’ and sample volumes were t5 1. for FIDanalyses, while MS identification required 10%300 I. The trap was sealed with Teflon stoppers after sampling and brought back to the laboratory. It was connected to the GCcolumn by an eight-port gas sampling valve and heated to 140°C. The components thus desorbed were purged with carrier gas (helium, 12 ml min- ‘) onto the first part (about 1SOmm) of the capillary column which was immersed in liquid nitrogen. In order to avoid plugging of flow by ice derived from water vapour adsorbed in the trap, a first loop of the capillary was supported above the surface of the liquid nitrogen. After 45min the valve was rotated, the cooled part of column heated to 140°C and the compounds were brought into the gas chromatograph. Collection of samples Samples were taken from two schoolrooms (A and B) in two different schools in two different residential city areas of Stockholm. Both schools were centrally heated. No smoking was allowed in the buildings and no other extreme pollutants were present. Room A was ventilated by a self draughting system only and the number of air changes per hour was determined by tracer gas measurements (made by the National Swedish Institute for Building Research). Room B was ventilated by an overflow system including exhaust valves inside the room. The number of air changes per hour was determined here by use of a hot wire anemometer connected to a hood. Air samples were taken from the schoolroom during 10 min periods at the beginning and at the end of a 45 min period either during a class session attended by 1S-20 pupils (16- 19 years old, boys and girls) or in the unoccupied room. Doors and windows were closed all the time and fresh air was supplied by the ventilation system only. For comparison, outdoor air samples were also analysed. To find out whether or not there were any organic sulfur compounds present, the air of Room B - unoccupied and occupied - and the outdoor air were analysed in a GC connected to a flame photometric detector (FPD). The air samples were collected in 1 I. gas burettes. (The analyses were made by SIK - the Swedish Food Institute.) In addition, in Room B, temperature and relative humidity were recorded continuousIy by a thermohygro~aph and the concentration of carbon dioxide was measured every 5 min by infrared s~trophotometry.
W-separation
und detection
The GC column was a wall coated open tubular stainless steel capillary (0.75 mm id. x 145 m) with UCON (a polypropyleneglycol) 50HB 2000 or 5100. It was programmed from 43 to 137°C at a rate of 2”min-‘. starting with an isothermal period of 8 min at 43’C. In the GC-MS analyses the capillary column and a helium make-up gas flow of 20 ml min - ’ were connected to the first stage of the jet-separator of the instrument. The concentrations of 15 compounds were determjned by using their peak heights recorded with the FID. Response factors were obtained by injecting standard aqueous solutions of reference compounds onto a packed column. The carrier gas flow, 12 ml min _ ‘_was the same as in the capillary column. The temperature was adjusted so as to give equal peak widths on both columns. The same calibration curves were used for related compounds.
RESULTS AND DISCUSSION
Figure 1 shows chromatograms. made of 1001. samples taken in (a) the outdoor air, (b) the unoccupied Room A. and (c) the same room during a class session, The volume is larger than the breakthrough volumes for many of the most volatile compounds, for which reason the peaks in the beginning of the chromatograms are about 10”, too small in comparison with the others. Table 1 lists the characterized compounds numbered according to the peaks numbered in the chromatograms. The structure ofeach hydrocarbon isomer has not been determined, and usually only the type of compound is given. Characterizations were based on MS and in some cases also on chromatographic retention. Table 1 shows that the qualitative composition of organic substances in the air is rather similar in all three cases : outdoors, unoccupied and occupied classroom. The aliphatic and aromatic hydrocarbons are predominant, followed by the halocarbons, and a few other compounds, e.g. acetone and ethanol. The number of components detected is larger in indoor than in outdoor air, 160 as compared to 50. Most of them are hydrocarbons; particularly the unsaturated compounds are more numerous indoors. For the quantitative analyses, sample volumes of only 15 I. were taken, so as to aliow proper proportions between the peaks, in light of the fact that the breakthrough volumes could not be reached. The method for quantitation is not very exact. Thus the results are presented as concentration ranges in Fig. 2. In this figure the mean concentration ranges of some components in the air of Room B, as well as in the outdoor air, are shown. The concentrations were always found to be higher indoors than outdoors and to increase when people were present in the room. This is a surprising finding because aliphatic and aromatic hydrocarbons are assumed to originate mainly from industrial and vehicular emissions. The question arrises : are outdoor components, like some hydrocarbons, enriched indoors and a~umulated in the air, or are such compounds simply generated by building
1373
Organic compounds in indoor air
i n
c
Temperature 43
43
50
60
70
80
f”Cf
90
100
110
120
130 137
r
0
I
10
20
30
40
50
Time tmin)
Fig. 1. ~asc~romato~a~ of 100 i. samples taken in (a) the outdoor air, (bf the ~~~u~i~ ~~offlr~orn and (c) the occupied schoolroom. (145 m x 0.75 mm WCON M HB 200DUT, 43°C 8 &a, 2” min- ’ to 137°C; scale on ordinate differs between the chromatograms.) AE:
El
Il.12
3
x
hexane
hexene
58 59
decene
x
x
x
x
x 60
u 4 known dodecane
C4-alkylbenrene c _ _#I_
C3-alkylbenzene
undecene
dadecene
C -alkylbenzene
dlpentene
C -alkylbenzenc
dodecarle undecene
styrene
undecene
dodecane
C?-alkylbenzenc
undecene
dodecane
136)
air
outdoor
Detected
in the. chromatograms.
21
x
(mw
) undecane
undecene
(n-
terpene
undecene
dddecene
C -alkylbenzene
undecene
dodecene
o-xylene
undecene
undecane
L
51
56
55
54
53
52
51
50
49
48
uodecene
undecane
decene
undecene
undecane
decene
undecyne
undecene
m-xylene
Compound
to the peaks numbered
x
heptene
nonene
nonane
heptane
heptene
octene
nonane
nonene
nonane
decane
benzene
oc tene x x
x
octene
heptene
x
x
x
nonane
octene
nonane
ethanol
octene
octane
x x x x x x x x x x ? 1 x x x x x x x x x x x x x x x x x x x x
47
45 46
44
“o
Peak
correspond
20
19
18
17
16
15
14
13
trichloroethane
caibontetrachloride
octane x
x
octane
9
pen tene
x x
x
hexene x
x
heptane
heptene
x
x
heptane
heptane
x
hexene x
x
i soprene
heptane
x x x
hexane
x
classroom
trichlorotrifluoroethane
8
10
n
x
x
i occupied
x
empty classroom
in air. The numbers
trichlorofluaromethane
air
outdoor
Detected
components
hexane
Compound
1. ldentifj~d
ace tone
6
4,s
no
Peak
Table.
x
x
x
x
x
x
x
x
empty classroom
i
n
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
7.
x
x
x
classroom
occupied
Organic compounds in indoor air
x
xx
-*xx
x
xx
*
*xxx
**
xxx
x
xx
1375
*
xx
x*
*
x
*
x
INGEGEFW
JOHANSON
to air quality is of minor importance. In this context it is interesting to note that inside hog farms no reduced organic sulfur compounds have been detected (flame photometry) in spite of the fact that liquid swine manure has an offensive odour (Grennfelt et al., 1977).
Fig. 2. Concentration components in outdoor and air from occupied theses in the figure
ranges [pgrnv3j of a selection of air, airfrom unoccupied schoolroom schoalroom. Numbers within parencorrespond to peak numbers in
~hrom~t~~rarns. materials, ventilation systems inventories, clothes, and humans ? It is obvious from the Fig. 2 that the acetone and ethanol concentrations vary most. They are higher in the uno~upied room than outdoors and increase substantially in the presence of humans (up to an average of24 and 55 c(g rnw3, respectively). One source of these substances is the human breath, which contains an average of 12~~grn-~ of acetone and 240pgm-3 of ethanol at 2O”C, 1 atm (Jansson and Larsson, 1969). With the actuaf air changes and with 0.5 m3 air breathed per person per hour the concentration ranges of acetone and ethanol would be 40_1OOfigm-” and 8%2Ofrgrn-’ respectively. The latter concentration is too low to account for alf of the ethanol measured in our study. Considerable amounts probably originate from perfumes and deodorant sprays. The total concentration of organic compounds were much higher in Room A than in Room B. This may be explained by the different ventifation capacities of the rooms: Room A underwent 0.7 air changes per hour corresponding to about 6 m3 air per person and hour. and Room B underwent 1.8 air changes per hour or about 15 mJ per person and hour. The outdoor concentration of carbon dioxide was 0.03 to 0.04% by volume and the same percentages were obtained in the empty classroom, even after a 45 min period of emptiness. The CO,-concentration did increase during the 45 min period in which pupils were present in the room (to about O.l-0.3%). This increase was correlated to the number of persons present. No organic sulfur compounds or hydrogen sulfide were found, either indoors or outdoors, even though the detection limit of the analytical method was as low as0.1 bigSm-3, This indicates that their contribution
The results of the air analyses show that the qualitative composition of indoor and outdoor air is about the same. Aliphatic and aromatic hydrocarbons predominate, but the number and concentrations of the compounds detected, especially the aliphatic ones, are higher indoors and increase in the presence of humans. Acetone and ethanol vary most and seem to be correlated to humans, and to rooms where humans have been. Carbon dioxide, on the other hand, is only correlated to the number of persons present at the moment, not to the room. Generally, we still know little about interactions between the constituents of the indoor air, as well as between these and the various materials in a room. The room perhaps acts as a “chemical reaction chamber”, for which reason the composition of the indoor air would not be exclusively defined by the composition of the inlet air and the materials in the room. Further investigations are necessary before an accurate description of the indoor air composition can be put forth. Moreover, we must also gain knowledge of the way odorous pollutants are generated and how they behave in rooms.
~~k~#~~ie~~~~n~e~l.s - This work is part of a joint project sponsored by the Swedish Board for Technical Development (proj. no. 75-3299) and by the Swedish Council for Building Research (proj. no. 750117-5, Dr. B. Berglund; proj. no. 750073-7, Dr. T. Lindvall). The author thanks Dr. B. Jansson, National Swedish Environment Protection Board, Professors A. Johansson and F. Ingman, Department of Analytical Chemistry at the Royal Institute of Technology, (Stockholm) for stimulatin~dis~ussions. Drs B. Berglund and T. Lindvall have given valuable comments on the manuscript. REFERENCES
Andersen I., Lundqvist G. R. and M#lhave L. (1975) Indoor air pollution due to chipboard used as a construction material. ~?~~o,~~~e~i~ ~~~~r~n~e~f 9, 1121-i 127. Bergert K.-H. and Betz V. (1974) Erfahrungen bei der quantitativen Analyse von Fliichtigen organ&hen Mikroverunreinigungen in Luft. Chromntographia 7, 681-687. Dravnieks A. and Whjt~eld J. (1971) Gas ~hromatographic study of air quality in schools. ASHRAE Trans. 77, 113.--1x Friberg L. and Ronge H. (1964) ffy@w. Scandinavian University Books, Stockholm. Grennfelt P., Lindvall T., Nor&n O., Rosen C. and Thyselius L. (1977) Odour emission and atmospheric dispersion from hog farms. JTI Report no. 13. Grab K. and Grob G. 11971) Gas-liquid chromatograPbi~-mass s~ctrometric investigation of C,X,, organic compounds in an urban atmosphere. J. ~~r~~a~~~~. 62, l-13.
Organic compounds in indoor air Jansson B. 0. and Larsson B. T. (1969) Analysis of organic compounds in human breath by gas chromatography-mass spectrometry. J. lab. c/in. Med. 74, 961-966. Kaiser R. E. (1973) Enriching volatile compounds by a temperature gradient tube. An&t. Chem. 45, 965-967. Kovats E. (1965) Gas chromatographic characterization of organic substances in the retention index system. Aduan. Chromatogr. 1, 229. Lonneman W. A., Kopczynski S. L., Darley P. E. and Sutterfield F. D. (1974) Hydrocarbon composition of urban air pollution. Environ. Sci. Technol. 8, 229-236. Pellizzari E. D., Bunch J. E., Berkley R. E. and McRae J. (1976a) Collection and analysis of trace organic vapor pollutants in ambient atmospheres. The performance of a Tenax GC cartridge sampler for hazardous vapors. Analyt. Letr. 9, 45-63.
1377
Pellizzari E. D., Bunch J. E., Berkley R. E. and McRae J. (1976b) Determination of trace hazardous organic vapor pollutants in ambient atmospheres by gas chromatography/mass spectrometry/computer. Analyt. Chem. 48, 803-807.
Raymond A. and Guiochon G. (1974) Gas chromatographic analysis of Cs-C,, hydrocarbons in Paris air. Environ. Sci. Tech&. 8, 143-148. Russel J. W. (1975) Analysis of air pollutants using sampling tubes and gas chromatography. Environ. Sci. Technol. 9, 1175-1178. Ryd H. (1967) An attempt to measure objectively the quality of air. The National Swedish Institute for Building Research. Report no. 34:1967. Versino B., de Groot M. and Geiss F. (1974) Air pollution sampling by adsorption columns. Chromatographia 7, 302-304.