AP02_02.vp © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 23 Acta Polytechnica Vol. 42 No. 2/2002 An optimum odor microclimate can be ensured by suit- able changes in (a) the source of odors, and (b) the transfer field between the source and the exposed subject. 1 Changes in the source of odors Reduction or, if possible, removal of the source of odors, is the most effective way: Construction materials that do not release an odor, and production technologies without odor sources should be preferred. Two examples of effective ways are quick setting coatings and waste baling presses. Quick setting coatings were developed in France. They consist of a great number of low-molecular compounds and of so-called photo-initiators, which, when radiated by UV rays, rapidly (within a second) change low-molecular compounds into high-molecular compounds. Natural materials are preferred for wood preservation, especially beeswax applied directly to cleaned wood. Waste baling presses are awailable for home kitchens. Waste baling presses are produced by the Lescha Company (Leonard Schmid, Augsburg, Germany). A balong press can from part of a kitchen furniture suite (Fig. 1). Waste (including champagne bottles) is pressed into a polyethylene package of small volume (1/4 of the original volume) (Fig. 2). Thus, of course, any odors, or microbe release from the waste is avoided. 2 Changes in the transfer field between source and subject Such changes can be made in the following ways: a) stop the odors from spreading within the building, b) supply an adequate quantity of outdoor air to the building interior, i.e., suitable ventilation, c) air filtration, d) introduction of plants, e) chemical deodorization, f) intensive air ionization, g) neutralization with ionized ozone, h) bake-out procedure. 2.1 How to stop odors from spreading within a building The most effective method is to be careful about the air streams produced by infiltration and by indoor heat sources. Staircases should be divided into several hermetic parts, and the sources of odors should be confined to the upper part of the building. The most serious problems occur in tall buildings, as a consequence of the stack effect (thermal upward pressure). According to some measurements, there is a negative pres- Optimization of the Odor Microclimate M. V. Jokl The odor microclimate is formed by gaseous airborne components perceived either as an unpleasant smell or as a pleasant smell. Smells enter the building interior partly from outdoors (exhaust fumes - flower fragrance) and partly from indoors (building materials, smoking cigarettes - cosmetics, dishes). They affect the human organism through the olfactory center which is connected to the part of brain that is responsible for controlling people’s emotions and sexual feelings: smells therefore participate to a high level in mood formation. Sweet smells have a positive impact on human feelings and on human performance. Criteria for odor microclimate appraisal are presented together with ways of improving the odor microclimate (by stopping odors from spreading within a building, ventilation, air filtration, odor removal by plants, deodorization, etc.), including so-called AIR DESIGN. Keywords: odors, microenvironment, hygiene, indor air quality, microclimate. Fig. 1: The Lescha-Mollpack waste baling press integrated into kitchen furniture Fig. 2: The product of the waste baling press: a small polyethyl- ene package sure in the lower part of a 16 to 30-storey building of 120 to 160 N � m�2. There is an underpressure of about 30 N � m�2, even at the front door of the nine-storey buildings often constructed in Europe (Fig. 3). This means, in practice, that in order to open a house-door sized about 1 × 2 m it is neces- sary to use a force equivalent to 6, 24 and 32 kg. The effect of the thermal uplift is increased vertically through the whole building (shafts, staircases), and there is intensive spreading of odors within the building if the staircase is not divided into several hermetic parts, or if the odor sources (kitchens, laboratories, etc.) are not located in the upper part of the building. If this is impossible, at least hermetically sealed doors should be used from the staircase to the apartments or offices. 2.2 Adequate quantity of outdoor air-ventilation Pettenkofer’s classic value provides a basic measure for rooms where people are the main source of air pollution. For optimum concentration of CO2 1000 ppm � 1800 �g/m 3 � � 0.1 vol. he prescribes 25 m3/ l � person. According to ASHRAE Standard 62-1989R this value can be accepted (after rounding to 7.5 l / s � person � 27 m3/ h � person) for an unadapted person, while for adapted persons it is decreased to 2.5 l / s � person (9 m3/ h � person). By these values applying the quantity of air delivered into a room can be adjusted to the number of people: with the increasing number of people the CO2 concentration also increases, and thus the air rate 24 © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ Acta Polytechnica Vol. 42 No. 2/2002 measured � �T 30 °C calculated H E IG H T [m ] � �p [ N m ] � 2 rooms staircase 12 STORY BUILDING 9 STORY BUILDING 10 20 30 neutral zone �400 �200 0 200 400 Fig. 3: The air pressure distribution within a nine-story building. On the left, a schematic representation of the air pressure in a building; on the right, calculated and measured air pressure. 15 20 °C- MACHINE ROOM LECTURE HALL 1 2 3 4 5 6 Fig. 4: The microclimate in a lecture hall controlled by a thermostat and a CO2 sensor (1 air rate sensor, 2 controlling flap, 3 electrical heater, 4 control unit, 5 room thermostat, 6 CO2 sensor) must be increased, e.g., by increased fan rotations controlled by a CO2 sensor in the room (see Fig. 4). Energy also in- creases, savings, an important factor, are made as a result of decreased energy consumption for warming outdoor air. The following equation should be used in the rooms where odor agents, released from building materials, are deci- sive for outdoor air rate: � � R G B B iTVOC e TVOC � �3 6. � � [l/s�m2] (1) where RB � minimum outdoor air rate related to 1 m 2 of floor [l/s�m2], GB � TVOC rate produced within an interior [�g/h�m2 floor] (see Table 1), �eTVOC � TVOC concentration in outdoor air [�g/m3] (see Table 2), �iTVOC � prescribed TVOC limit [�g/m3] (see Table 2 and Fig.6). The required outdoor air rate is the sum of the two air rates (if they occur), i.e., calculated from TVOC and based on CO2. An air change (the number of times that the air in a room is changed during one hour) is often prescribed. Thus the outdoor air rate can be obtained if the air change is multi- plied by the room volume. The value calculated in this way, can differ from the outdoor air rate, which is estimated from the air rate necessary for one person, as it is evident from the following examples. Example 1: Lecture hall crowded with students. The outdoor air rate related to one person can be lower than the prescribed value, e.g., 27 m3/h�person, i.e., too low, even if high air change six has been taken into account. Example 2: A hangar in which one person is repairing an air- plane. The outdoor rate related to one person can be much higher than the prescribed value, e.g., 27 m3/h�person, i.e., excessively high, even if only air change one has been taken into ac- count. The outdoor air rate related to one person is decisive in each case, i.e., if calculations are based on air change, the re- © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 25 Acta Polytechnica Vol. 42 No. 2/2002 Location TVOC [�g�h�1�m�2 floor] Author Note Mean Range Existing buildings, offices 1,550 100–4,890 EUR 14449 EN (1992) Converted olf value Working hours (9–11) 360 132–691 Ekberg (1993) Night-time (5–7) – 90–467 Ekberg (1993) Schools (classrooms) 1,550 620–2,780 EUR 14449 EN (1992) Converted olf value Kindergartens 2,060 1,030–3,810 EUR 14449 EN (1992) Converted olf value Assembly halls 2,570 670–6,790 EUR 14449 EN (1992) Converted olf value Dwellings 720 360–1,080 EUR 14449 EN (1992) New PVC floor tiles 795 450–1,400 Brown and Crump (1993) Low-polluting buildings (target values) – 260–510 EUR 14449 EN (1992) Converted olf value Solid flooring materials (vinyl, carpet, chipboard) Typical below 55 Crump et al (1997) Emission rates constant Wall and ceiling materials Crump et al (1997) Emission rates constant Plasterboard max 6 6-mm plywood max 10 15-mm plywood max 12 Bitumienised fibre board as- phalt max 30 Crump et al (1997) Emission rates constant PVC skirting board Below the detection limit Crump et al (1997) Polythene spacer 4 when heated to 40 °C Rockwool (cavity wall) Below 15 Crump et al (1997) Emission rates declined slowly Table 1: TVOC Emission rates in a building interior sults must be proved by calculations of air rates related to one person. Furthermore, if recirculation is used in an air han- dling system, the outdoor air rate must not be lower than 10 % of all air delivered into the room. 2.3 Air filtration There must be a special material for odor absorption: acti- vated carbon, charcoal or synthetic resin (e.g., amberlite). Odors can also be removed by an odor scrubber (odor wash- er), a biowasher, catalytic burning, biofilters, and even by plants [6]. Activated carbon has better odor-removing properties than charcoal (carbonized wood). It is produced by the impact of hot steam (800–1000 °C) and zinc chloride on charcoal. This process enlarges and purifies the cells. As a result, the in- ternal surface is enlarged up to 500–1500 m2/g, i.e., in aver- age to an unbelievable value of 1000 m2/g. Other kinds of coal and peat are also used and, even coconut shells (see Fig. 5). Activated carbon absorbs very little air humidity, and does not change the chemical or psychrometric condition of the air. The odor removal efficiency depends on the contact pe- riod of the gas with the carbon. For least 80 % efficiency, and an air velocity of 2.5 to 3.0 m/s, the thickness of the carbon layer should be 2.5 cm. The efficiency depends on the carbon retention: the absorbed odor quantity [g] is related to 100 g of carbon (see Table 3). Activated carbon is mostly applied in air cleaners. It is evi- dent from the retentions presented in Table 7 that this device is not efficient against all odors in the same way: some odors are trapped very efficiently (e.g. human body odors), others are only slightly reduced, e.g., fish odors (odors of prepara- tions for plant protection). 26 © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ Acta Polytechnica Vol. 42 No. 2/2002 Location TVOC [�g � m�3] CO2 [ppm] Source Note At sea 0 300–340 ICAO 1964, EUR 14449 EN Converted decipol value In a city, good air quality 14 15–18 350 EUR 14449 EN Ekberg 1993 Converted decipol value In a city, bad air quality 71 23–98 350–400 EUR 14449 EN Brown and Crump, 1993 Converted decipol value Table 2: TVOC and CO 2 concentrations in outdoor air Carbonised Coconut Shell Carbonised Wood Activated Coal Activated Coconut Shell Fig. 5: Microscope photos of carbonized and activated coal 2.4 Odor removal by plants Indoor plants can be used as room detectors and CO2 consumers, and some are also able to clean the air from ace- tone, benzene, CO, ethanol, formaldehyde, methanol, SO2, toluene and some VOCs (see Table 4). A lawn can be effective in an atrium: an area of 15 × 15 m is a sufficient source of oxygen for a family with four members, and it also cleans SO2, CO2 and hydrogen fluoride from the air. It has not been explained satisfactory what is going on with these absorbed chemicals: whether they are only stored, or perhaps used for energy consumption. It has already been proven by NASA that some of them nourish microorganisms that grow on and near the roots. Therefore flowers in a vase or plants growing in hydroponics are useless for this purpose. Potted plants growing in substrate enriched by active carbon are benefi- © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 27 Acta Polytechnica Vol. 42 No. 2/2002 Odor agent Retention [%] [g/100 g coal] Solutions 25 to 35 Exhaust gases 20 Body odor 35 Ether 15 Onion, garlic 15 Antiseptics 30 Tobacco smoke 25 Aliphatic mercaptans (oil refineries, chemical industry) 1 Aromatic mercaptans (oil refineries, chemical industry) 15 Aliphatic amines (fishing indistry) 1 Higher hydrocarbons (>C14) (chemical industry) 15 Aliphatic chlorohydrocarbons (chemical industry) 15 Plant protection chemicals (agriculture stocks, chemical industry) 0.2 Table 3: Retention values for activated coal (charcoal) Odor agent Source Affecting plants 1 Acetone Body odor Lily 2 Benzene Office solvents Chrysanthemum Gerberum Lily 3 Ethanol Alcoholic beverages Lily cleaning agents 4 Hydrogen fluoride Glass processing Grass 5 Formaldehyde Wood products, especially Aloe plywoods and chipboards Azalea parquet sealants Philodendron cork Gum-tree laminates Lily glues Poinsettias cleaning agents and Table 4: Odor removal by plants cial. One well-developed plant with air streaming uniformly around it at a velocity of 0.10-0.15 m/s should be used for 9 m2 of floor area. 2.5 Deodorization Deodorization is the masking of odors: covering an un- pleasant odor by another, stronger and more pleasant smell, a so-called deodorant: formaldehyde, acetaldehyde, ozone, etc. However deodorants cannot be used in high concentra- tions owing to their toxicity: e.g., an ozone concentration should not exceed 0.1 mg/m3 (0.5 ppm). Deodorization has been known for a long time. Incense has been used for ages. It is made by cutting the shrub Boswellis carteri. From notches cut into the tree, milk juice flows, which forms yellow balls in the air, called incense (alibanum). It contains 4 to 7 % of ethereal oils. If it is burnt on glowing coals, pleasant smelling smoke is produced. Now- adays incense is used as an ingredient in scented candles, and is mixed with scented woods to produce a special smelling material used during Christmas. 2.6 Intensive air ionization Odors can also be removed by intensive ionization of the air, i.e., by forming negative aeroions of high concentration. Even the typical odor of a bar can be removed during the night in this way, so that the room can be used for serv- ing breakfast the following day. Air cleaners equipped with ionizers thus have a new field of application. 2.7 Neutralization with ionized ozone Ionized ozone is a very effective oxidant: the molecules of odor agents are cracked and changed into water vapors, carbon dioxide and other substances (without bad smells). The ozone concentrations must be watched carefully due to its toxicity. This method should be applied at night, when no 28 © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ Acta Polytechnica Vol. 42 No. 2/2002 Odor agent Source Affecting plants disinfectants Tulip cosmetics open fireplaces gas cookers tobacco smoke textiles 6 Methanol Cleaning agents Lily 7 Sulphur dioxide Cars, boiler rooms Grass 8 Toluene Cleaning agents Arek palm, Lily 9 Trichloroethylene Cleaning agents Lily 10 VOC Cleaning agents Philodendron carpets Golden potos glues paintings rubbish solvents 11 Exhaust fumes Cars Chesnut tree outside air intake intake air duct air handling system recirculating air duct supply air distribution duct return air ductionized ozone generator Fig. 6: Odor removal by ionized ozone people are present. Ionized ozone is supplied to recirculated air (see Fig. 6). 2.8 Bake-out procedure A new way of removing VOC from a building interior is the so-called BAKE-OUT PROCEDURE: the indoor temper- ature is raised to 30–38 °C for two or more days, and simulta- neously the ventilation is increased [4]. This is even required by the authorities in the State of California. Practical experi- ence has not yet been reported in the literature. References [1] BSR/ASHRAE Standard 62-1989 R Ventilation for Accept- able Indoor Air Quality. [2] EUR 14449 EN. Quidelines for Ventilation Requirements in Buildings. Report No. 11. Commission of EC, Luxem- bourg, 1992. [3] Fanger, P. O.: Introduction of the olf and the decipol units to quantify air pollution perceived by human indoors and out- doors. Energy and Buildings Vol.12, No. 1/1988, p. 1–6. [4] Hicks, J. et al: Building Bake-Out During Commissioning: Effects on VOC Concentration. In: Proc. of the Fifth Int. Conf. on Indoor Air Quality and Climate, Vol. 3. To- ronto (Can.), 1990. [5] IAQU. Odor evaluation as an investigative tool. Indoor Air Quality Update, 1991, p.10–13. [6] Jokl, M.: Microenvironment: The Theory and Practice of Indoor Climate. Springfield (Illinois, U.S.A.) : Thomas Publisher, 1989, p. 416. [7] Jokl, M.: The Theory of Indoor Environment of Buildings. In Czech. Praha: Vydavatelství ČVUT, 1993, p. 261. [8] Jokl, M. V., Leslie, G. B., Levy, L. S.: New approaches for the determination of ventilation rates: the role of sen- sory perception. Indoor Environment Vol. 2, No. 2/1993, p. 143–148. [9] Jokl, M. V.: Evaluation of indoor air quality using the decibel concept. Int. J. of Environmental Health Research Vol. 7, No. 4/1997, p. 289–306. [10] Kaiser, E. R.: Odor and its measurement. In: Air Pollution. Academic Press, 1962, p. 50–527. [11] Mc Burney, D. H., Levine, J. M., Cavanaugh, P. H.: Psy- chological and social ratings of human body odor. Personality and Social Psychology Bulletin No. 3/1977, p.135–138. [12] Oseland, N. A.: A review of odor research and the new units of perceived air pollution. Watford: BRE, 1993, p. 24. [13] Parine, N.: The use of odor in setting ventilation rates. Indoor Environment Vol. 3, No. 3/1994, p. 87–95. [14] Pettenkofer, M.: Über den Luftwechsel in Wohngebauden. München, 1858. [15] The Human Body. Bratislava: GEMINI, 1992 Miloslav V. Jokl, Ph.D., Sc.D, University Professor phone: +420 2 2435 4432 fax: +420 2 3333 9961 e-mail: miloslav.jokl@fsv.cvut.cz Czech Technical University in Prague Faculty of Civil Engineering Thákurova 7 166 29 Prague 6, Czech Republic © Czech Technical University Publishing House http://ctn.cvut.cz/ap/ 29 Acta Polytechnica Vol. 42 No. 2/2002