WO1991002972A1

WO1991002972A1 - Method for evaluation of air pollution and an apparatus for implementation of the method

Info

Publication number: WO1991002972A1
Application number: PCT/DK1990/000218
Authority: WO
Inventors: Povl Ole Fanger
Original assignee: Povl Ole Fanger
Priority date: 1989-08-25
Filing date: 1990-08-23
Publication date: 1991-03-07
Also published as: DK421789D0; AU6340890A; DK164074C; DK421789A; DK164074B

Abstract

Method and apparatus for evaluating perceived air pollution by means of sensory organs in the human nasal cavity. The apparatus has at least one inhalation aggregate (1) comprising an emission chamber (2) with a pollution emission element (3), a ventilation element (4) which can ventilate the emission chamber (2) with a known airflow, and an air outlet (5). The inhalation aggregate (1) is in the area between the pollution emission element (3) and the inhalation area (5) supplied with a diffuser section (6) to secure that the ventilation airflow from the emission chamber (2) can be inhaled without being mixed with extraneous air. The cross sectional area of the airflow in the inhalation area (5) is at least 40 cm2 and the ventilation airflow is at least 15 l/min, preferably 45 l/min. By means of the apparatus and the method it is possible, in a practical way, to use the newly introduced measuring units for perceived air quality, ''decipol'' and ''olf''.

Description

METHOD FOR EVALUATION OF AIR POLLUTION AND AN APPARATUS FOR IMPLEMENTATION OF THE METHOD

The invention concerns a method for evaluating air pollu- tion by means of the sensory organs in the human nasal ca¬ vity as well as an apparatus for applying the method.

For many years there has been an acute need for a quantita¬ tive determination of perceived air quality, especially within buildings. Numerous discussions and articles on so- called "sick buildings" reveal a demand for a new method for evaluating air quality. A scientific basis for a quan¬ titative specification of perceived air pollution was established with the introduction of the measuring units "decipol" and "olf". Decipol is a unit for perceived air quality; it predicts the number of people that could be ex¬ pected to be dissatisfied with the air. Olf is the corre¬ sponding unit for the strength of the sources polluting the air. The two units were introduced and defined by Fanger in "Energy and Buildings", Vol. 12 (1988) pp. 1-6.

For example the air quality in a space within a building may be evaluated in decipol by a panel of trained subjects who compare the air quality with references, i.e. known air qualities with established decipol values. On the basis of the determined air quality in decipol and a measured out¬ door air supply to the space, the strength of the pollution sources in the space can be determined in olf.

Polluted air, especially outdoors in industrial areas, has hitherto been evaluated by the dilution principle. For example the American patent bulletin No. 3902851 describes an apparatus which, by diluting polluted air with unpollu¬ ted air, can find the dilution ratio where the pollution is no longer perceived. This equipment is intended to be used in evaluating odour emissions from industrial plants.

A similar apparatus for comparing odour impressions is des¬ cribed in the German patent bulletin No. 29 14 635. The odiferous air is diluted with pure air, the principle being to register the dilution ratio at which the subject no lon¬ ger can perceive the odour.

The dilution principle measures the pollution concentration in relation to the odour threshold independent of whether or not the pollution is perceived as annoying. Therefore the principle cannot determine air quality in decipol as this unit quantifies annoyance and dissatisfaction.

In the Swedish patent bulletin No. 409 763 with priority from FR 72 43805 an apparatus is described for comparing the intensity of odour in two air currents, one current be¬ ing blown into each nostril. The subject registers the point at which both nostrils receive equal odour intensity. This equipment is unsuitable for evaluating perceived air quality and thus also for determining air quality in deci¬ pol.

In ASTM-E-544-75, 1984 yearbook for ASTM standards, an ol- factometer is described which compares the intensity of an unknown odour with a reference odour emitted in varying concentrations from a number of small ports. However it is odour intensity that is compared here, and not annoyance which is expressed by the decipol unit. Moreover, the flow of polluted air from the individual ports is rather weak so the depth of inhalation, its rate, as well as the distance of the nose from the port, can lead to large variations of the concentration in the nasal cavity. The apparatus can¬ not, therefore, determine air pollution in decipol. Other sources mentioning odour evaluation and apparatus for odour measurement are as follows:

B. Berglund, U. Berglund and T. Lindvall, Theory and me- thods for odor evaluation, Experimantia 42 (1986), pp 280- 287. Barnebey-Cheney Co. Scentometer, An instrument for field-odor measurements, A manual, Columbus, Ohio: Barnebey-Cheney Co., 1970. T. Lindvall, On sensory evalua¬ tion of odorous air pollutant intensities, Nordisk hygiej- nisk tidsskrift, supplementum 2, Stockholm 1970. D.G. Li¬ ang, H. Panhuber, R.I. Bakter, 1978, Olfactory properties of amines and n-butanol, chemical senses and flavour 3, pp. 149-166. Misco company, Dynamic olfactometer, model 7250, Data sheet, Berkeley, California. Misco Microchemical spe- cialities Company, 1974. A. Dravnieks, Instruction manual for dynamic dilution binary scale olfactometer, IIT Re¬ search Institute. .C.L. Hemeon, Technique and apparatus for quantitative measurements of odor emissions, J. Air.poll.cont.Assoc. 18, 1968, pp. 166-170. D.G. Liang, Characterisation of human behaviour during odour percep¬ tion, Perception, 1982, vol. 11.

Neither has it been possible, with known techniques descri¬ bed in the scientific literature, to perform measurements of perceived air quality with the accuracy required to ex¬ press meaningful decipol values.

The purpose of the invention is therefore to present a me¬ thod for determining air pollution by means of the sensory organs in the human nasal cavity and an apparatus for doing so. The method should enable the achievement of reproduc¬ ible measurements preferably expressed in decipol and olf.

The method according to the invention, _^applies an apparatus with at least one inhalation aggregate consisting of an emission chamber with a pollution emission element, a ven¬ tilation element that can ventilate the emission chamber with a specific airflow and an air outlet where the pollu¬ ted air is inhaled and evaluated. The method is characteri- zed by an airflow larger than the highest momentary airflow during inhalation by a person, and by the application of an apparatus which secures that the part of the known airflow that is inhaled is not diluted with an unknown air quantity prior to inhalation. This has the advantage that the person evaluating the air quality is able not only to evaluate whether the air pollution is strong or weak but, with expe¬ rience, is also able to gauge the evaluation so precisely that the degree of air pollution can be quantified. As the maximum inhalation airflow for some subjects is slightly more than 10 1/min and for the majority of subjects can be up to 40 1/min, the airflow should be at least approximate¬ ly 12 1/min but preferably at least approximately 45 1/min. To ensure a suitable reserve it is best to choose an air¬ flow somewhat greater than those mentioned, for example ap- proximately 60 1/min.

When using an apparatus with several inhalation aggregates in which at least one pollution emission element produces a known air pollution, the air quality evaluation will be im- proved and thus of greater absolute accuracy. If the air polluted with the known air pollution is evaluated partly by human inhalation and partly by a quantitative instrumen¬ tal measurement, for example by using a gas analysis appa¬ ratus based on photoacoustical spectroscopy, there is a possibility of generating a known chemical standard pollu¬ tion.

To express the perceived air pollution in decipol units it is advantageous, when using an apparatus with several inha- lation aggregates with different known air pollutions and whit at least one inhalation aggregate where the air pollu¬ tion is unknown, that the unknown pollution is evaluated by comparing inhalation from the aggregate with the unknown air pollution with inhalation from one or more inhalation aggregates with known and calibrated air pollution.

Surprisingly, it has been shown that there is a unambiguous relation between the concentration of 2-propanone (acetone) and the perceived air quality expressed in decipol. Irre- spective of the type of pollution, it is therefore an ad¬ vantage to choose this chemical compound as pollution com¬ ponent in the inhalation aggregates with the known degree of air pollution. When the perceived air quality is deter¬ mined in decipol, the strength of the unknown pollution source in the apparatus can be determined in olf by a simp¬ le calculation.

The apparatus for applying the method can be characterized as given in characterizing part of claims 6-9. The advanta- ge of the respective variants is that individually they are each of them suitable for use with one of the above-mentio¬ ned ways of carrying out the method.

The invention is described below, using a particularly fa- vourable apparatus design, given as an example. Reference is made to the drawing, reference numbers in the various figures referring to the same elements. By illustration the following is shown in:

Fig. 1 - an inhalation aggregate according to the inven¬ tion;

fig. 2 - an apparatus for determining perceived air qua¬ lity according to the invention, with five inhala- tion aggregates (see Fig. 1); and fig. 3 - a diagram showing the relationship between per¬ ceived air quality expressed in decipol and the content of 2-propanone expressed in ppm in actual- ly pure air.

Fig. 1 shows an inhalation aggregate 1 according to the invention. This aggregate 1 comprises an emission chamber 2 which can be e.g. a glass container with a capacity of a few litres. The emission chamber has an air intake 7, through which fresh unpolluted air can be drawn in. In the emission chamber 2 there is a pollution emission element 3. This could be a pollution source emitting a qualitatively and quantitatively known pollution for example by evapora- tion of a chemical substance at a known rate; it could also be an unknown source emitting a qualitatively and/or quan¬ titatively unknown air pollution. The emission chamber 2 has an air outlet with a ventilation element 4 that can provide a known ventilation of the emission chamber of at least 15 1/min, preferably more, e.g. approximately 60 1 of air per min. The ventilation element 4 leads the ventilati¬ on air via a diffuser 6 to an inhalation area 5. It is es¬ sential that the airflow passage from the air intake 7 to the inhalation area 5 is designed in such a way that the airflow cannot be mixed with extraneous air. It is an ad¬ vantage if the airflow in the inhalation area has a suitab¬ ly large cross section. It has been shown that the cross section should be at least 40 cm² or even larger, e.g. ap¬ proximately 50 cm². If an emission chamber 2 of a manageab- le size is used, for example approximately 3 litres, the cross section of the ventilation airflow at the outlet from the emission chamber 2 is considerably smaller. It is then beneficial to include a diffuser section between the air outlet of the emission chamber 2 and the inhalation area, the angle of the outlet in the diffuser section being no greater than 8. It has been shown that with such an outlet angle one can avoid any mixing of the ventilated airflow with ambient air at the end of the diffuser section, in the inhalation area. With a larger outlet angle there is a risk that ambient air, to a greater or lesser degree, can be drawn into the ventilation airflow in the area around the diffuser section outlet.

The inhalation aggregate shown in Fig. 1 can of course be designed in many ways; for example the ventilation element can be designed so that it "blows" ventilation air into the emission chamber 2 instead of, as shown here, drawing the ventilation air in through this chamber. If the inhalation aggregate is used for inhaling air polluted by an unknown source, the strength of which is to be measured, it can be beneficial to design the ventilation element with for example two air fans, one ventilating the emission chamber as described above, and the other mixing the ventilated airflow with a certain amount of unpolluted air in the area around the air outlet in the emission chamber. If the un¬ known source pollutes the ventilation air to such an extent that it lies above the measurable value, one can try mixing the ventilation air with a certain amount of fresh air, for example in a mix ratio of 1:5. If a measurable air pollu- tion in the inhalation area is achieved in this way, the strength of the air pollutant in the ventilated air can be calculated by simple multiplication.

Fig. 2 shows five inhalation aggregates 11, 12, 13, 14 and 15, according to Fig. 1. Together, these five inhalation aggregates comprise an apparatus for the quantitative de¬ termination of air pollution according to the invention. Each of the inhalation aggregates 11, 12, 13 and 14 inclu¬ des an emission element providing a known air pollution. The figure shows, by numbers, that ventilated air from ag- gregate 11 is polluted 1 decipol, the air from aggregate 12 is polluted 5 decipol and similarly the pollution from ag¬ gregate 13 and 14 is 10 and 20 decipol respectively. The air pollution from the emission element in the fifth inha- lation aggregate 15 is unknown.

It has proved beneficial to use as known pollutants, sour¬ ces that evaporate 2-propanone. This substance is one of many known and unknown substances found in human bioefflu- ents and it has been shown, surprisingly, that the percei¬ ved air quality, defined as the impression given by these many substances when inhaled, can be reproduced with air containing 2-propanone alone. It has been shown, moreover, that there is a simple and linear interdependence between the content of 2-propanone in air and the perceived air quality expressed in decipol. This relationship is depicted in the diagram shown in Fig. 3.

The method for measuring perceived air pollution and ex- pressing this in decipol units, according to the invention, is described in the following by means of an example, using the apparatus shown in Fig. 2.

A panel of trained inhalers chooses the apparatus shown in Fig. 2 with five inhalation aggregates 11, 12, 13, 14 and 15, each ventilated with a known airflow, e.g. 50 1/min of unpolluted air.

Aggregates 11, 12, 13 and 14 comprise emission elements providing airflows polluted respectively at 1, 5, 10 and 20 decipol. These values are advantageously produced by evapo¬ rating 2-propanone at rates that result in the ventilated air from each of these inhalation aggregates containing the concentration of 2-propanone corresponding to the degree of pollution concerned (see Fig. 3). The emission element in the fifth inhalation aggregate 15 produces an unknown air pollution resulting in a degree of pollution in the ventilated air between 1 and 20 decipol.

One or more of the persons inhales in turn in the inhala¬ tion area of each aggregate (the central area of the venti¬ lation outlet at the end of the diffuser section) ventila¬ tion air with unknown degree of pollution (see Fig. 1) and gives a first evaluation. The subject then inhales air from one or more of the inhalation aggregates 11, 12, 13 and/or 14 in a similar way, possibly intermittently inhaling air with the unknown degree of pollution. After only a few in¬ halations, a trained person can quantify the degree of pollution in the emitted air having an unknown degree of pollution. If a more accurate determination is desired than that given by one person, an evaluation by several trained subjects can be requested.

Should the unknown pollution be greater than 20 decipol, there are two obvious possibilities for attaining a precise measurement of the pollution source strength. One can either dilute the ventilation air with a higher but known flow of unpolluted air until a degree of air pollution is achieved that is within the measuring range, or in certain cases one can reduce the strength of the pollution source by a known factor.

The above explanation only describes the apparatus and me- thod according to the invention, for illustration and exemplification purposes. An expert could device many vari¬ ations within the scope of the invention. For example the apparatus can be used for training subjects, the rate of pollution produced in the inhalation aggregate with the unknown pollutant being known to the trainer but not to the trainee. The learning process becomes simpler and much quicker than previously in this way. The apparatus could be designed in many other forms than the one shown, for examp¬ le the diffuser section could be either horizontal or cur¬ ved. The essential requirement for the apparatus is that the ventilation airflow must be known and the form of the apparatus must secure against this known ventilation air¬ flow being mixed with unknown, extraneous air, prior to in¬ halation.

Claims

P A T E N T C L A I M S

1. Method for the quantitative evaluation of air, e.g. pol¬ luted air, by allowing human subjects to evaluate the air by means of inhalation, characterized in:

a) the evaluation being carried out by comparing with reference values produced by an apparatus and establis¬ hed by standardization, e.g. on the basis of decipol u- nits, their respective annoyance-producing strengths be¬ ing known;

b) an airflow being directed from the apparatus towards the subject's nose at a rate higher than the highest in¬ halation rate; and

c) that it is secured that the airflow is not mixed with extraneous air.

2. Method according to claim 1 is characterized by the use of 2-propanone (acetone) in establishing the reference va¬ lue.

3. Method according to claim 1 or claim 2 is characterized also by:

- making a physical measurement of the air, e.g. a mea- surement of the degree of pollution in relation to a particular substance;

- investigating whether there is a relationship between the evaluations made by human subjects and those based on physical measurements; and - if there is a relationship, making use of the physical measurements.

4. Apparatus for carrying out the method according to one or more of claims 1-3, supplied with an inhalation aggrega¬ te consisting of:

- an emission chamber with a pollution emission element,

- a ventilation element designed to ventilate the emis¬ sion chamber with a known airflow, and

- an air outlet where the polluted air is inhaled for evaluation,

characterized by having a diffuser in the area between the pollution emission element and the air outlet, the cross sectional area at the outlet being at least 40 cm² and the ventilation airflow being at least 15 1/min, preferably over 45 1/min.

5. Apparatus, according to claim 4, characterized by having several inhalation aggregates.

6. Apparatus, according to claim 4 or claim 5, characteri¬ zed by the diffuser having an outlet angle of at most 8°.

7. Apparatus, according to claim 4, 5 or 6, characterized by at least one of the pollution emission elements emit¬ ting, at a known rate, a known air pollution component, e.g. 2-propanone (acetone).