WO2013182822A1

WO2013182822A1 - Method and device for the continuous and maintenance-free measurement of particles in the air

Info

Publication number: WO2013182822A1
Application number: PCT/FR2013/051303
Authority: WO
Inventors: Bruno Aubert
Original assignee: Cairpol
Priority date: 2012-06-06
Filing date: 2013-06-06
Publication date: 2013-12-12
Also published as: FR2991772A1; FR2991772B1

Abstract

The method consists of circulating air of which the particle content is to be measured, through a virtual impactor (11) of which one branch is provided with a filter (14) in order to store the particles that are not to be measured (particles of a diameter greater than 10 μm, for example) and to measure only the dangerous particles such as particles of a diameter less than 2.5 μm, for example. The high quality of this separation of particles on the basis of the granulometric distribution of same and, above all, the absence of maintenance of the associated device make it possible, preferably, to implement a miniature nephelometer (apparatus implementing nephelometry) at low cost in order that the apparatus can be used individually by the largest number (individual monitoring, home, etc.) for measuring particle concentration. A first application is therefore a miniature personal alert device that can be worn on the wrist or on the belt, to alert vulnerable persons of the presence of a high level of particles. The small size and reduced cost of the device also make it possible to use it in all air-conditioning systems in order to warn people of the need to increase the ventilation or change the filter.

Description

METHOD AND DEVICE FOR CONTINUOUS MEASUREMENT AND WITHOUT MAINTENANCE

OF PARTICLES IN THE AIR

TECHNICAL FIELD OF THE INVENTION

The subject of the present invention is a method and a device for continuous and maintenance-free measurement of particles in the air. The present invention applies, especially to systems to prevent people, including people with fragile health, risks incurred if they expose themselves to too polluted air. It is noted that the particles considered can be solid or liquid. The present invention aims, in particular, to instantaneously detect, in the immediate environment of a user, particulate pollutants of a predetermined size suspended in air, the quantity of which would be greater than a predetermined limit value, by example provided by the public health services, and to warn that user.

STATE OF THE ART

It is known that, to be able to measure the particles, the majority of the apparatuses must first make a classification of these in order to measure only one granulometric slice. Indeed, the particles, beyond their chemical toxicity present a greater or lesser risk depending on their size. Large particles with a diameter greater than 2.5 μιτι and less than 10 μιτι are arrested on the one hand in the upper respiratory tract of man and, on the other hand, sediment rapidly in the atmosphere and so are quickly harmless.

Conversely, the very fine particles (less than 2.5 μιτι, called "PM2.5") or even ultrafine (less than 1 μιη, called "PM1") are stopped only at the level of very low lower pathways ( at the level of the cells) and can therefore pass directly into the blood. This presents a risk all the more dangerous as the particles are chemically toxic or are in the presence of other pollutants (Europe announced 348 000 premature deaths per year related to these particles). In addition, very fine particles or ultrafine sedimentent practically do not sediment and are found for a very long time suspended in the air.

Of course, the measurement of particles smaller than 10 μιτι (called "PM10") well integrates PM2.5 ultrafine particles but they generally represent a small, not necessarily constant, of all particles. The knowledge of only PM10 particles does not allow to have an idea of the PM2.5 particle concentration, the most dangerous.

It is therefore necessary to be able to measure PM2.5 particles (or even PM1 particles) from separating them from larger particles.

This operation can be carried out thanks to impactors that stop large particles and let the finest. Unfortunately, this technique has the disadvantage that the impactor quickly loses its effectiveness as and when the impact of the particles. It is then necessary to clean and / or regenerate the impactor periodically which is an expensive operation in time and not very accessible to the general public.

Another technique is to use filters. But these filters clog quickly and / or see their ability to let only the particles to be measured to degrade. There are also cyclone separators but these, beyond the fact that they have a significant footprint, require a speed and especially a high air pressure that require the implementation of air pumps that consume energy and therefore hardly compatible with a nomadic use.

Finally, as described in US Pat. No. 8,104,362 "In-Line Virtual Impactor for Scalping Large", there are virtual impactors that have the advantage of no longer having an impact surface but that must implement two independent aspirations including that who is in charge of the suction of large particles which must be directed outside the measuring system.

These two independent aspirations complicate the system and do not allow to consider a miniaturization of the device.

OBJECT OF THE INVENTION

The present invention aims to remedy all or part of these disadvantages. For this purpose, the present invention aims, in a first aspect, a device for measuring the amount of particles in the air, which comprises:

an air suction means for measuring the particle content,

a virtual multi-branch impactor positioned on the air path, upstream of the suction means, for separating particles of different dimensions,

on at least one of said branches, a filter configured to retain particles that must not be measured and

a means for measuring the quantity of particles leaving at least one branch of the virtual impactor including at least one branch of the virtual impactor provided with a filter.

Thanks to these arrangements, the particles of different dimensions are separated on two branches of the virtual impactor, the particles are filtered on at least one of these branches and the amount of residual particles is measured. It is thus possible, at very low cost, to measure the level of particles in a range of dimensions, in particular the rate of particles of smaller dimensions.

The inventors have found that the device of the present invention had an efficiency greater than 80% compared to the efficiency of a conventional sampling head, close to 50%.

In embodiments, the device that is the subject of the present invention comprises means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means.

Thanks to these provisions, a single suction means, for example a single fan or a single mini-pump, may be sufficient to operate the device. In addition, particles of smaller dimensions, which would have followed the path of larger particles, pass through the filter that holds the larger particles and can be measured.

In embodiments, the means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means is positioned upstream of the means for measuring the quantity of particles.

Thanks to these provisions, the measuring means can measure the quantity of all the particles passing through the device. In embodiments, the means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means is positioned downstream of the means for measuring the quantity of particles.

Thanks to these arrangements, the measuring means can measure the quantity of the only particles according to one of the branches of the virtual impactor, in the particle size range that this branch selects.

In embodiments, a pipe of the air flow entering the measuring means is substantially oriented perpendicular to the plane of air flow in the virtual impactor.

Thanks to these arrangements, the compactness of the device is improved.

In embodiments, the suction means is a single fan or a single pump configured to draw air into each of the branches of the virtual impactor.

Thanks to these provisions, the cost of the device object of the present invention is further reduced.

In embodiments, the filter is made of hydrophilic material to dampen the variations of humidity of the air.

Thanks to these provisions, the influence of the variations of humidity of the air on the result of the measurement is reduced. In particular, when a user passes from the inside of a building to the outside, the sudden change in the humidity rate of the air is attenuated in the measurement.

In embodiments, the air suction means is positioned downstream of the measuring means, on the air path.

Thanks to these provisions, it is avoided that the risks of destruction or evaporation of the particles to be measured at the level of the suction means disturb the measurement.

In embodiments, the virtual impactor includes: a first part configured to orient at least part of the air flow entering in a first direction and

a second part configured to separate the flow of air directed in the first direction between:

a flow of air making a first angle with said direction and carrying particles of first dimensions and

an air flow forming a second angle, greater than the first angle, carrying particles whose dimensions are, on average, greater than the average dimension of the particles of first dimensions.

Thus, the virtual impactor is particularly compact, the particles of smaller dimensions along the path having the highest angle.

In embodiments, the first portion separates the incoming air flow into two air streams oriented symmetrically with respect to a plane of symmetry and the second portion has a symmetrical shape with respect to said plane of symmetry.

Thanks to these provisions, the risk of clogging of the virtual impactor is reduced by the multiplicity of paths.

In embodiments, the air path section between the first and second portions is increasing along the air path.

With these features, the effectiveness of the virtual impactor is improved because the smaller sized particles have a speed that reduces along the virtual impactor.

In embodiments:

the means for measuring the quantity of particles is a nephelometer,

the means for measuring the quantity of particles is configured to perform optical counting,

the means for measuring the quantity of particles is configured to perform a beta absorption on a collector filter,

the means for measuring the quantity of particles is configured to determine a change in mass of an oscillating piece or

the means for measuring the quantity of particles is configured to measure a condensation of the particles.

Thanks to each of these provisions, the measurement of the quantity of particles has the precision of the physical principle used. In embodiments, each filter configured to retain particles that are not to be measured is placed on each leg of the virtual impactor carrying the medium-sized particles.

Thanks to these provisions, only the quantity of particles of smaller dimensions, which are the most dangerous for man, is measured.

In embodiments, the device which is the subject of the present invention further comprises an electronic circuit equipped with a microprocessor configured to compare the value of the particulate concentration measured by the means for measuring the quantity of particles with at least one value. predetermined limit and to issue an alert signal if exceeding a said limit value.

Thanks to these provisions, the user, especially if his health is fragile, can be alerted that the particle rate exceeds a recommended limit value.

In embodiments, the device that is the subject of the present invention comprises a single power supply and data transmission connector representative of the measurement made by the measuring means.

Thanks to these provisions, the device of the present invention can be connected to a computer, possibly portable computer tablet and / or a cell phone.

According to a second aspect, the present invention aims a method for measuring the amount of particles in the air, which comprises:

an air suction step whose particle content is to be measured,

a step of separating particles according to their dimensions, by implementing a virtual impactor with several branches positioned on the air path, upstream of the suction,

a filtering step, on at least one of said branches, with a filter configured to retain particles that must not be measured and

a step of measuring the quantity of particles leaving at least one branch of the virtual impactor including at least one branch of the virtual impactor equipped with a filter.

According to a third aspect, the present invention aims at a device for measuring the quantity of particles in the air, which comprises:

an air suction means for measuring the particle content, a virtual multi-branch impactor positioned on the air path, upstream of the suction means, for separating particles of different dimensions,

a means for measuring the quantity of particles leaving at least one branch of the virtual impactor,

wherein a pipe of the air flow entering the measuring means is substantially oriented perpendicular to the plane of air flow in the virtual impactor.

According to a fourth aspect, the present invention is directed to a device for measuring the amount of particles in the air, which comprises:

an air suction means for measuring the particle content,

wherein the suction means is unique and is configured to draw air into each of the branches of the virtual impactor.

Since the advantages, aims and characteristics of this method and of those devices that are the subject of the second to fourth aspects of the present invention being similar to those of the device that is the subject of the first aspect of the present invention, they are not recalled here.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages, aims and features of the present invention will emerge from the description which follows, for an explanatory and non-limiting purpose, with reference to the appended drawings, in which:

FIG. 1 schematically represents, in a section C-C, from above, a first particular embodiment of the device that is the subject of the present invention,

FIG. 2 schematically represents, in a section AA, the device illustrated in FIG. FIG. 3 schematically represents, in a section BB, the device illustrated in FIGS. 1 and 2,

FIG. 4 represents, in the form of a logic diagram, steps for implementing the method that is the subject of the present invention,

FIG. 5 represents, schematically and in sectional view, a second particular embodiment of the device that is the subject of the present invention, and

- Figure 6 shows schematically and in sectional view, a third particular embodiment of the device object of the present invention. DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

It is noted, as of now, that Figures 1 to 3 are not to scale and that the covers, enclosures or closure covers, power supplies, data processing circuits and communication connectors, are not represented .

As represented in FIGS. 1 to 3, in one embodiment, the device 10 for measuring the amount of particles in the air comprises, in a housing 1 1:

a suction means 19 for the air whose particle content is to be measured,

a virtual impactor consisting of two parts 12 and 13, with several branches symbolized by arrows 17 and 18, virtual impactor positioned on the air path, upstream of the suction means 19, to separate particles of different dimensions,

on at least one of said branches 18, a filter 14 configured to retain particles that must not be measured and

a means 20 for measuring the quantity of particles leaving at least one branch of the virtual impactor, of which at least one branch 18 of the virtual impactor provided with a filter 14.

For example, the device measures three centimeters by four centimeters. Its height is five millimeters.

An air flow 16 enters the housing 1 1 through the action of a miniature fan 19, preferably a single fan or a single mini pump, a flow rate of one to five liters / minute, positioned in the outlet 15. This air outlet 15 is preferably orthogonal to the plane of air flow in the impactor 12, 13. Part 12 is a flow concentrator 12, which focuses the air entering a vein just before encountering the flow separator 13.

The virtual impactor 12, 13 comprises, in this embodiment:

a first portion 12 configured to orient at least a portion of the incoming airflow in a first direction and

a second part 13 configured to separate the flow of air oriented in the first direction between:

In embodiments, the first portion 12 separates the incoming air flow into two air streams oriented symmetrically with respect to a plane of symmetry and the second portion has a symmetrical shape with respect to said plane of symmetry. The risk of clogging the virtual impactor is thus reduced by the multiplicity of paths.

It can be seen in FIG. 1 that the section of the air path between the first and the second part is increasing along the air path. The effectiveness of the virtual impactor is thus improved because the smaller sized particles have a speed that reduces along the virtual impactor, as the section increases.

The flow separator 13 is positioned above the orthogonal suction outlet 15 so that the outlet 15 is separated into two parts of different areas and whose ratio of the rear surfaces (for the airflow 18) over before (for the air flow 17) is between 1, 1 and 20.

The smaller part of the suction outlet 15 draws the secondary air stream 18, which does not undergo a deflection at the flow separator 13. The largest part of the suction outlet 15 draws the flow main air 17 which has undergone the greatest deviation at the separator 13. The precise dimensions of the concentrator 12, the separator 13 and the housing 1 1 thus allow large particles continue their course substantially rectilinearly into the filter 14 where they will be stopped. Conversely, the fine particles, entrained by the air flow 17, pass directly into the suction outlet 15. The measuring means is located in or opposite the suction outlet 15.

Each filter 14 configured to retain particles that must not be measured is placed on each branch of the virtual impactor carrying the particles with the average dimensions are the highest, to measure only the amount of smaller particles, which are the most dangerous for the man.

It can be seen in FIGS. 1 and 3 that the suction means 19 is preferably located downstream of the measuring means 20. Thus, the particles do not pass into the suction means 19 before entering the measuring means 20. It is thus avoided that shear forces at the blades of the fans (whose speed may be greater than 20 m / s) or at the level of the pump membrane lead to the fractionation of the particles, or even to their evaporation in case of liquid particles, which would distort the measurement, possibly by a factor of two to three.

In embodiments:

the means 20 for measuring the quantity of particles is a nephelometer,

the means 20 for measuring the quantity of particles is configured to perform optical counting,

the means 20 for measuring the quantity of particles is configured to perform a beta absorption on a collecting filter,

the means 20 for measuring the quantity of particles is configured to determine a change in mass of an oscillating piece or

the means 20 for measuring the quantity of particles is configured to measure condensation of the particles.

The measurement of the quantity of particles has the precision of the physical principle thus used.

A more elaborate version of the device implements a virtual impactor with three branches, to allow the measurement of several granulometric slices such as PM1 particles and PM2.5 particles. Advantageously, the filter 14 is made of hydrophilic material so that the flow of air 18 which passes through is buffered in moisture. It avoids the artifacts often observed in the measurement of particles, namely that in case of sudden change in humidity, especially when passing from the inside of a building to the outside, the particle size may vary abruptly. and temporarily involving measurement errors.

Of course, the filter 14 ends up clogging and must then be changed, but the very low costs achieved make it possible to consider replacing purely and simply the entire device every year or every two years, in order to avoid a re-calibration that would have been more expensive. The term "maintenance free" of the present invention then corresponds to a lack of maintenance during the lifetime of the device.

The device 10 also implements a device for measuring the concentration of particles such as a nephelometer, an electronic circuit equipped with a microprocessor making it possible to compare the values of particulate concentrations with the regulatory thresholds of the pollutants and to alert the persons individually. Exceeding an air pollution threshold, harmful to health.

A visual alarm (a light-emitting diode, a liquid crystal display), audible (buzzer) or vibrating (vibrator), reliable is given by an electronic circuit managing the levels of alerts.

A first application is an individual alert device worn on the wrist or belt, which alerts asthmatics or cardiovascular patients to the presence of a peak of pollution to particles or pollens so that they adapt their activity and thus reduce the risk of asthma attacks or infarcts, respectively.

A second application of the device is home automation, the device being powered by a USB type connector and regularly transmitting measurement results to a central monitoring of a local, for example professional to prevent its occupants from a peak pollution .

The small size and low cost of the device 10 also allows it to be used in all air conditioning systems to warn of the need to increase ventilation or change the filter. Other implementation details of embodiments of the device that is the subject of the present invention are given below.

The virtual impactor 12, 13 separates the particles of different dimensions on at least two branches. The particles are filtered on at least one of these branches and the amount of residual particles is measured. It is thus possible, at very low cost, to measure the level of particles in a range of dimensions, in particular the rate of particles of smaller dimensions.

In embodiments such as that illustrated in FIGS. 1 to 3, a means for joining the air passing through at least two branches of the virtual impactor upstream of the particle quantity measuring means makes it possible to use only a single fan or a single mini-pump. The cost of the device is thus further reduced and its compactness is improved.

In addition, particles of smaller dimensions, which would have followed the path of larger particles, pass through the filter that holds the larger particles and can be measured.

In embodiments such as that illustrated in FIGS. 1 to 3, a ducting of the air flow entering the measuring means is substantially oriented perpendicularly to the air circulation plane in the virtual impactor, which improves the air flow. compactness of the device.

In embodiments, the device of the present invention further comprises an electronic circuit (not shown) having a microprocessor configured to compare the particle concentration value measured by the particle quantity measuring means. with at least one predetermined limit value and for issuing an alert signal if a said limit value is exceeded. The user, especially if his health is fragile, can be alerted that the particle rate exceeds a recommended limit value.

Preferably, the device which is the subject of the present invention comprises a single power supply and data transmission connector representative of the measurement made by the measuring means. The device which is the subject of the present invention can thus be connected to a computer, possibly portable, to a computer tablet and / or to a cellular telephone, by a USB type connector. It should be noted that, as a variant, only the fine particles passing through one of the branches of the virtual impactor are measured, preferably by positioning the measuring means before the meeting of the air flows by the single suction means or by providing two suction means. In these two cases, preferably, the direction of the air flow entering the measuring means is substantially perpendicular to the plane of the air flows in the virtual impactor.

As seen in FIG. 4, in a particular embodiment, the method for measuring the amount of particles in the air comprises:

a suction step 50 of the air whose particle content is to be measured,

a step 51 of separating particles according to their dimensions, by implementing a virtual impactor with several branches positioned on the air path, upstream of the suction,

a step 52 of filtering, on at least one of said branches, with a filter configured to retain particles that must not be measured,

a step 53 of measuring the quantity of particles leaving at least one branch of the virtual impactor including at least one branch of the virtual impactor provided with a filter,

a step 54 for comparing the quantity of particles measured with at least one predetermined limit value, for example provided by the health authorities and possibly adapted to the state of health of the wearer of the device and

a step 55 of issuing an alert when the measured quantity of particles exceeds the predetermined limit value and transmitting the measured data.

Preferably, the transmission of the measured data is done via a single connector serving both to power the device and to the transmission of data and program updates, for example according to the USB standart (acronym Universal Serial Bus for universal serial bus, connector standard). Preferably, the device also comprises a battery recharged by this connector and a temporary storage memory of the collected data and the crossing of limit values. Tests have shown that the device and method of the present invention have an efficiency greater than 80% compared to the efficiency of a conventional sampling head, close to 50%.

FIG. 5 shows, in the second embodiment 60 of the device forming the subject of the present invention, the same components as in the first embodiment 10, with the exception of the filter 14 and the measuring means 20. The means 20 is replaced by a measuring means 61 which measures only the quantity of particles leaving the internal branch of the virtual impactor 12 and 13 conveying the air flow 17.

FIG. 6 shows, in the third embodiment 70 of the device that is the subject of the present invention, the same components as in the first embodiment 10, with the exception of the measuring means 20, which is replaced by a means measurement 71 which measures only the amount of particles leaving the outer branch of the virtual impactor 12 and 13 conveying the air flow 18.

In each of the particular embodiments illustrated in FIGS. 1 to 3, 5 and 6, the device 10, 60 or 70 for measuring the amount of particles in the air comprises:

a suction means 19 for the air whose particle content is to be measured,

a virtual impactor 12 and 13 with several branches positioned on the air path, upstream of the suction means, for separating particles of different dimensions,

measuring means 20, 61 or 71 of the quantity of particles leaving at least one branch of the virtual impactor,

wherein a pipe of the air flow entering the measuring means 61 is substantially oriented perpendicularly to the plane of air flow in the virtual impactor 12 and 13.

In each of the particular embodiments illustrated in FIGS. 1 to 3 and 5, the device 10, 60 or 70 for measuring the amount of particles in the air comprises:

a suction means 19 for the air whose particle content is to be measured, a virtual impactor 12 and 13 with several branches positioned on the air path, upstream of the suction means, for separating particles of different dimensions,

wherein the suction means 19 is unique and is configured to draw air into each of the branches of the virtual impactor 12 and 13.

In these particular embodiments, the device that is the subject of the invention comprises means for joining the air passing through at least two branches of the virtual impactor 12 and 13 upstream of the suction means.

In the first embodiment, this means for joining the air passing through at least two branches of the virtual impactor 12 and 13 upstream of the suction means 19 is positioned upstream of the measuring means 20 of the quantity of particles.

On the contrary, in the second and third embodiments, this means for joining the air passing through at least two branches of the virtual impactor 12 and 13 upstream of the suction means is positioned downstream of the measuring means 61 or 71. the amount of particles.

In embodiments (not shown), the device is provided, for at least two branches of the virtual impactor 12 and 13, a measuring means 61 and 71 for the amount of particles leaving each of said branches of the virtual impactor, each measuring means 61 and 71 providing a signal representative of a quantity of particles in a different range of particle sizes.

Claims

claims

1. Device (10, 60, 70) for measuring the amount of particles in the air, characterized in that it comprises:

an air suction means (19) for measuring the particle content,

a virtual impactor (12, 13) with several branches positioned, on the air path, upstream of the suction means, for separating particles of different dimensions,

on at least one of said branches, a filter (14) configured to retain particles that must not be measured and

- means (20, 61, 71) for measuring the amount of particles leaving at least one branch of the virtual impactor including at least one branch of the virtual impactor provided with a filter.

2. Device according to claim 1, which comprises means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means.

3. Device according to claim 2, wherein the means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means is positioned upstream of the particle quantity measuring means.

4. Device according to claim 2, wherein the means for joining the air passing through at least two branches of the virtual impactor upstream of the suction means is positioned downstream of the particle quantity measuring means.

5. Device according to one of claims 1 to 4, wherein a pipe of the air flow entering the measuring means is substantially oriented perpendicularly to the plane of air flow in the virtual impactor.

6. Device according to one of claims 1 to 5, wherein the suction means is a single fan or a single pump configured to suck the air in each of the branches of the virtual impactor.

7. Device according to one of claims 1 to 6, wherein the filter consists in part of hydrophilic material to dampen variations in humidity of the air.

8. Device according to one of claims 1 to 7, wherein the air suction means is positioned downstream of the measuring means, in the path of air.

9. Device according to one of claims 1 to 8, wherein the virtual impactor comprises:

a first part configured to orient at least part of the air flow entering in a first direction and

10. Device according to claim 9, wherein the first part separates the incoming air flow into two air streams oriented symmetrically with respect to a plane of symmetry and the second part has a symmetrical shape with respect to said plane of symmetry. .

1 1. Device according to one of claims 9 or 10, wherein the section of the path of air between the first and the second part is increasing along the path of the air.

12. Device according to one of claims 1 to 1 1, wherein the means for measuring the amount of particles is a nephelometer.

13. Device according to one of claims 1 to 1 1, wherein the means for measuring the amount of particles is configured to perform optical counting.

14. Device according to one of claims 1 to 1 1, wherein the means for measuring the amount of particles is configured to achieve a beta absorption on a collector filter.

15. Device according to one of claims 1 to 1 1, wherein the means for measuring the amount of particles is configured to determine a change in mass of an oscillating piece.

16. Device according to one of claims 1 to 1 1, wherein the means for measuring the amount of particles is configured to measure a condensation of the particles.

17. Device according to one of claims 1 to 1 6, wherein each filter configured to retain particles that must not be measured is placed on each branch of the virtual impactor carrying the particles whose average dimensions are the highest. .

18. Device according to one of claims 1 to 17, which further comprises an electronic circuit provided with a microprocessor configured to compare the particle concentration value measured by the particle quantity measuring means with at least one predetermined limit value and for issuing an alert signal in case of exceeding a said limit value.

19. Device according to one of claims 1 to 18, which comprises a single power supply connector and data transmission representative of the measurement made by the measuring means.

20. A method for measuring the amount of particles in the air, characterized in that it comprises:

an air suction step whose particle content is to be measured, a step of separating particles according to their dimensions, by implementing a virtual impactor with several branches positioned on the air path, upstream of the suction,