CN114080257B - Pollution-proof mask with pollution sensing - Google Patents

Abstract

An anti-contamination mask includes an inhalation portion and an exhalation portion that detect a user's respiratory cycle. Particle or contamination sensors are used to sense the interior of the air chamber and provide a sensing result. The sensing results for the plurality of inhalation or exhalation portions are combined to derive a combined sensing result. This allows for a sufficient sensing period during only the inhalation portion or only the exhalation portion in order to obtain accurate sensing results.

Description

Pollution-proof mask with pollution sensing

Technical Field

The present invention relates to anti-contamination masks, in particular masks comprising contamination sensing.

Background

According to the World Health Organization (WHO), 400 tens of thousands of people die each year from air pollution. This problem stems in part from the outdoor air quality of the city. The worst of these is the indian city, such as de, whose annual pollution level exceeds the recommended level by a factor of 10. However, even in european cities like london, paris and berlin, the pollution levels are higher than what is recommended by WHO.

Since this problem cannot be ameliorated significantly in a short period of time, the only way to solve this problem is to put on the mask, which provides cleaner air by filtration.

The most basic passive mask includes an outer wall that defines an air chamber between the outer wall and the face of the user when the mask is worn. The filter forms a boundary between the air chamber and the surrounding environment outside the air chamber. Thus, the user breathes through the filter.

To enhance comfort and effectiveness, one or two fans may be added to the mask. These fans are turned on during use and are typically used at a constant voltage. For efficiency and life reasons, these fans are typically electrically commutated brushless DC fans.

The benefit of using a powered mask by the wearer is that the slight strain on the lungs caused by inhalation against the resistance of the filter in a conventional non-powered mask can be relieved.

Furthermore, in conventional passive (non-powered) masks, inhalation may also cause a slight negative pressure within the mask, resulting in leakage of contaminants into the mask, which may prove dangerous if toxic. The power mask steadily delivers airflow to the face and may, for example, provide a slight positive pressure, which may be determined by the resistance of the exhalation valve, to ensure that any leakage is outward rather than inward.

There are several advantages if the operation or speed of the fan can be adjusted. This may be used to improve comfort by more proper ventilation during inhalation and exhalation sequences, or may be used to improve electrical efficiency. The latter translates into longer battery life or increased ventilation.

To adjust the fan speed, the pressure within the mask may be measured and both pressure and pressure changes may be used to control the fan.

For example, the pressure within the mask may be measured with a pressure sensor, and the fan speed may be varied based on the sensor measurements. For example, pressure sensor measurements may be used to detect the respiratory cycle of a user, and the fan may be controlled according to the phase of the respiratory cycle.

Alternative pressure sensors exist for monitoring the pressure within the mask. WO2018/215225 discloses a mask in which the rotational speed of the fan is used as a representation of the pressure measurement. The pressure or pressure change is determined based on the rotational speed of the fan. Using this pressure information, the breathing pattern of the user may be tracked.

When the mask is being worn, it is desirable to detect the air quality within the mask to indicate that the filter is working and properly functioning to remove air pollution, as desired.

Thus, it is known to be desirable to incorporate a contamination sensor within a mask. However, within the mask, air alternates between inhaled air (entering the lungs through the filter) and exhaled air. The duration of the breathing cycle is for example in the range between 4 seconds (sitting) and 2 seconds (running).

Over time, average levels of contamination inside the mask have received limited attention. However, pollution sensing is particularly interesting for inhaled (and/or exhaled) air. It is therefore desirable to be able to perform contamination sensing during selected portions of the respiratory cycle (e.g., only inspiration). Many sensors require some time to reach a stable sensing signal (e.g., some types of optical particle sensors require 10 seconds). This is not due to the physical detection process, but in order to obtain enough samples to give reliable results.

In the case of a mask, the time of one inhalation or exhalation cycle is insufficient to give a stable reading. Thus, how to provide detection associated with the user's breathing cycle remains a problem.

US 2018/0325022 discloses an air filtration and analysis system with a sensor for use in. The characteristics of the inhaled and/or exhaled air are collected. The sensor may have a sensing window that is gated based on inspiration and expiration timing. CN104922822 discloses a mask with pollution detection.

Disclosure of Invention

According to an example of an aspect of the present invention, there is provided an anti-contamination mask comprising:

an outer wall for defining an air chamber between the outer wall and a face of a user when the mask is worn;

A filter for forming a boundary between the air chamber and an ambient environment outside the air chamber;

a detection circuit for detecting an inhalation portion and an exhalation portion of a user's respiratory cycle;

a particle or contaminant sensor for sensing the interior of the air chamber and providing a sensing result;

a timer; and

a controller adapted to:

timing a combined duration of the plurality of inspiratory portions using a timer, combining sensing results from the detection circuit for the plurality of inspiratory portions, and deriving a combined inspiratory sensing result for the target combined duration; and/or

The combined duration of the plurality of expiratory portions is timed using a timer, the sensed results from the detection circuit regarding the plurality of expiratory portions are combined, and a combined expiratory sensed result for the target combined duration is derived.

The invention relates to an anti-pollution mask. This means a device which is mainly aimed at filtering the ambient air breathed by the user. The mask does not perform any form of patient treatment. In particular, the pressure levels and flows caused by fan operation are only intended to help provide comfort (by affecting the temperature or relative humidity within the air chamber) and/or help provide airflow through the filter without requiring significant additional respiratory effort by the user. The mask does not provide full breathing assistance compared to the case where the user is not wearing the mask.

Such anti-contamination masks have particle or contamination sensors for sampling data across multiple respiratory cycles, so that enough data is obtained from the inhalation or exhalation cycles to be combined into a single reading. When the target duration of the sensing window is reached, sufficient data is obtained. The number of respiratory cycles required depends for example on the duration of each respiratory cycle, wherein faster breathing requires more respiratory cycles.

Even in combination, the inhalation and exhalation portions cover only a small portion of the total breath time. The inspiratory portion and the expiratory portion of each respiratory cycle are acquired. The complete respiratory cycle consists of an inhalation portion and an exhalation portion, but during the transition between these portions there is a mixture of inhaled/exhaled air. Thus, sampling may exclude the time periods corresponding to these transition phases, and only sample air during the core period of each phase.

The mask may also include, for example, a fan for drawing air from outside the air chamber into the air chamber interior and/or drawing air from inside the air chamber to the outside. Thus, the present invention may be applied to active masks. This already includes, for example, a detection circuit for detecting the inhalation and exhalation parts of the user's breathing cycle, as this information can be used for fan control. For example, the fan speed may be controlled in synchronization with the user's breathing cycle to conserve power. For example, the fan may be turned off during inspiration or expiration. Therefore, the invention can be implemented with little overhead.

The detection circuit is for example used to detect the inhalation and exhalation parts based on the pressure inside the air chamber (and in particular with respect to the ambient pressure). The pressure increases during exhalation and decreases during inhalation. The detection circuit may include a pressure sensor, such as a cavity pressure sensor or a differential pressure sensor.

Alternatively, the detection circuit may comprise means for determining the rotational speed of the fan, and a controller adapted to derive the pressure between the air chamber and the surrounding environment from the rotational speed of the fan, such that the fan speed is used as a representation of the pressure measurement.

In this way, the fan speed (for fans driving air into the chamber and/or exhausting air from the chamber) may be used as a representation of the pressure measurement. To measure the fan speed, the fan itself may be used, so that no additional sensor is required. In normal use, the chamber may be closed such that pressure fluctuations within the chamber have an effect on the loading conditions of the fan and thereby alter the electrical characteristics of the fan. This avoids the need for a separate pressure sensor.

In one example, the fan is driven by an electronically commutated brushless motor, and the means for determining the rotational speed comprises an internal sensor of the motor. Internal sensors have been provided in such motors to effect rotation of the motor. The motor may even have an output port on which the internal sensor output is disposed. Thus, there is a port carrying a signal suitable for determining the rotational speed.

Alternatively, the means for determining the rotational speed may comprise a circuit for detecting a ripple of the power supply supplied to the motor driving the fan. The ripple source induces a change in the supply voltage from the closing current through the motor coil due to the finite impedance of the input voltage source.

The fan may be a two-wire fan and the circuit for detecting ripple includes a high pass filter. The additional circuit requirements for a motor that already does not have a suitable fan speed output can be kept to a minimum.

The controller may be adapted to:

continuously collecting sensing results during a plurality of respiratory cycles; and

creating a subset of sensing results related to the plurality of inspiratory portions to derive a combined inspiratory sensing result; and/or

A subset of the sensing results associated with the plurality of expiratory portions is created to derive a combined expiratory sensing result.

Thus, in practice, the sensor may measure continuously and the sensing results are post-processed to create a sample associated with the respiratory cycle.

Alternatively, the controller may be adapted to:

performing sensing at selected times corresponding to the plurality of inspiratory portions to derive a combined inspiratory sensing result; and/or

Sensing is performed at selected times corresponding to the plurality of exhalation portions to derive a combined exhalation sensing result.

In this case, the sensor may be turned off outside of the selected time, or isolated from the air flow.

The controller may be adapted to:

implementing a low pressure threshold below which the inspiratory portion is identified; and/or

A high pressure threshold is implemented above which the expiratory portion is identified.

Thus, inhalation and exhalation are monitored based on the pressure threshold.

In one set of examples, the low and/or high pressure thresholds are set according to a respiration rate. Faster breathing (e.g., during exercise) is typically deep breathing with greater pressure swing. Thus, different thresholds may be applied for different exercise levels.

In another set of examples, the low and/or high pressure thresholds are dynamically adjusted based on the pressure within the air chamber during the previous inhalation and/or exhalation portions. Thus, different breathing cycles will result in different sampling windows.

Particle or contaminant sensors include, for example, light sensors based on light scattering. Which can be used to measure particle concentrations, such as PM2.5 levels.

The filter comprises, for example, an outer wall of the air chamber and forms a boundary directly between the air chamber and the surrounding environment outside the air chamber. This provides a compact arrangement, avoiding the need for a convection delivery channel, and a greater filtration area is achieved because the mask body performs the filtering function. This means that the user is able to inhale through the filter. The filter may have multiple layers. For example, the outer layer may form the body (e.g., fabric layer) of the mask, and the inner layer may be used to remove finer contaminants. The inner layer may then be removable for cleaning or replacement, but the two layers may be considered to together form a filter, as air is able to pass through the structure and the structure performs a filtering function.

The fan may be used only to draw air from inside the air chamber to the outside. In this way, the supply of fresh filtered air to the air chamber is facilitated at the same time, even during exhalation, thereby improving user comfort. In this case, the pressure inside the air chamber may be always lower than the external (atmospheric) pressure, so that fresh air is always supplied to the face.

The present invention also provides a method of measuring the level of particles or contamination within an air chamber of an anti-contamination mask, the method comprising:

detecting an inspiratory portion and an expiratory portion of a user's respiratory cycle;

sensing a level of particulate or contamination within an air chamber of the mask; and

timing a combined duration of the plurality of inspiratory portions, combining sensing results for the plurality of inspiratory portions, and deriving a combined inspiratory sensing result for the target combined duration; and/or

The combined durations of the plurality of expiratory portions are timed, the sensing results for the plurality of expiratory portions are combined, and a combined expiratory sensing result for the target combined duration is derived.

The method may include continuously collecting the sensing results during a plurality of respiratory cycles; and comprises:

Creating a subset of sensing results related to the plurality of inspiratory portions to derive a combined inspiratory sensing result; and/or

A subset of the sensing results associated with the plurality of expiratory portions is created to derive a combined expiratory sensing result.

Alternatively, sensing may be performed at selected times corresponding to a plurality of inhalation portions to derive a combined inhalation sensing result, and/or at selected times corresponding to a plurality of exhalation portions to derive a combined exhalation sensing result.

Inhalation and/or exhalation may be monitored by implementing a low pressure threshold below which inhalation is identified and/or a high pressure threshold above which exhalation is identified. The low and/or high pressure thresholds may be set based on the respiration rate. The low pressure threshold and/or the high pressure threshold may be dynamically adjusted based on the pressure within the air chamber during the previous inhalation and/or exhalation portions.

Drawings

Examples of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings:

figure 1 shows a contamination mask including particle or contamination sensing.

FIG. 2 illustrates one example of pressure monitoring system components;

fig. 3A shows the rotation signals during inspiration and during expiration, and fig. 3B shows how the fan rotation speed varies with time; and is also provided with

Fig. 4 shows a circuit for controlling the current through one stator of a brushless DC motor;

FIG. 5 shows a generic design of an optical particle sensor that can be used as a sensor of the present invention;

FIG. 6 shows the method of the invention in schematic form;

FIG. 7 shows three respiration waveforms for respiration during sitting, walking, running;

FIG. 8 shows three respiration waveforms and static thresholds for respiration during sitting, walking, running;

FIG. 9 shows three respiration waveforms and dynamic thresholds for respiration during sitting, walking, running; and is also provided with

Fig. 10 illustrates a method of measuring particle or contamination levels within the air chamber of an anti-contamination mask.

Detailed Description

The present invention will be described below with reference to the accompanying drawings.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, system and method, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, system, and method of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to designate the same or similar components.

The invention provides an anti-contamination mask comprising an inhalation portion and an exhalation portion that detect the respiratory cycle of a user. A particle or contaminant sensor is used to sense the interior of the air chamber and provide a sensing result. The sensing results for the plurality of inhalation or exhalation portions are combined to derive a combined sensing result. This allows for a sufficient sensing period during only the inhalation portion or only the exhalation portion in order to obtain accurate sensing results.

Figure 1 shows a contamination mask including particle or contamination sensing.

There is shown a subject 10 wearing a mask 12, the mask 12 covering the nose and mouth of the subject. The purpose of the mask is to filter the air before the subject inhales. For this purpose, the mask body itself serves as an air filter 16. Air is drawn into an air chamber 18 formed by the mask by inhalation.

The mask detects the respiratory cycle of the user and monitors the timing of the respiratory cycle. In the illustrated example, during inspiration, the outlet valve 22 (e.g., a check valve) closes due to the low pressure within the air chamber 18.

The mask also includes a sensor 24 for measuring the level of particulates or contamination within the air chamber 18. Which produces a sensing result.

In the example shown in fig. 1, the sensor 24 is connected in series with the fan, and thus the fan generates an airflow through the sensor. The sensor may be mounted behind the fan and check valve. The electrical components are for example all integrated together, thereby reducing the amount of wiring required. However, the sensor may be located elsewhere within the mask cavity, so long as the air flow is able to pass through.

Sensing the air quality within the mask can allow the user to be confident that the filter is working and that the air within the mask is healthy. If the response time of the sensor is greater than the various parts of the breathing cycle, it is not sufficient to measure only the air mass inside the mask, as sensing will then mix inhaled and exhaled air. The user typically wants to know the quality of the inhaled air and this should not be mixed with the exhaled air, as the exhaled air may be cleaner due to particles deposited in the lungs. Thus, the average measurement of the mask internal air mass over a long period of time (of multiple breaths) is not optimal.

The filter 16 may be formed solely of the mask body or may have multiple layers. For example, the mask body may include an outer cover formed of a porous fabric material that acts as a prefilter. Inside the housing, a finer filter layer is reversibly attached to the housing. The finer filter layer may then be removed for cleaning and replacement, while the outer cover may be cleaned, for example, by wiping. The housing also serves a filtering function, for example, to prevent large debris (e.g., soil) from entering the finer filter, which is used to filter fine particulate matter. There may be more than two layers. The multiple layers together act as a total filter for the mask.

When the subject exhales, air is expelled through the outlet valve 22. The valve is open to enable easy exhalation, but is closed during inhalation. Fan 20 assists in removing air through outlet valve 22. Preferably, more air is expelled than exhaled, so that additional air is supplied to the face. This increases comfort as the relative humidity and cooling are reduced. During inspiration, unfiltered air is prevented from being inhaled by closing the valve. Thus, the timing of the outlet valve 22 depends on the breathing cycle of the subject. The outlet valve may be a simple passive check valve operated by a pressure differential across the filter 16. However, it may alternatively be an electrically controllable valve based on sensing of the respiratory cycle.

The respiratory cycle is detected based on pressure changes within the mask volume. If the mask is worn and the user is breathing, there will be a varying pressure within the chamber. In particular, the chamber is closed by the face of the user. The pressure within the closed chamber will also vary according to the breathing cycle of the subject when the mask is worn. When the subject exhales, a slight pressure increase will occur, and when the subject inhales, a slight pressure drop will occur.

If the fan is driven at a constant drive level (i.e., voltage), different dominant pressures will appear as different loads on the fan because there are different pressure drops across the fan. This changing load will then result in a different fan speed. Thus, the rotational speed of the fan may be used as a representation of the pressure measurement across the fan. This is the preferred embodiment, as fewer sensors are used.

However, the inventive concept may be implemented with a pressure sensor for acquiring respiratory characteristics.

For a known pressure (e.g., atmospheric pressure) on one side of the fan, pressure (or proxy pressure) monitoring enables the pressure, or at least pressure change, on the other side of the fan to be determined. For example, the other side is a closed chamber, and thus has a pressure different from the atmospheric pressure.

The pressure change detected based on the monitoring of the fan speed or by pressure measurement is then used to obtain information about the user's respiration. In particular, the first value may represent a depth of respiration and the second value may represent a respiration rate.

The means for determining the rotational speed may comprise an already existing output signal from the fan motor or a separate simple sensing circuit may be provided as an additional part of the fan. However, the fan itself is used in both cases, so that no additional sensor is required.

Fig. 2 shows one example of a system component. The same components as in fig. 1 are denoted by the same reference numerals.

In addition to the components shown in fig. 1, fig. 2 also shows a controller 30, a local battery 32, and a device 36 for determining fan speed.

As described above, the controller 30 performs detection of the timing of the respiratory cycle, as well as the sensor signal processing functions. In particular, the controller is configured to combine the sensing results for the plurality of inspiratory portions and derive a combined inspiratory sensing result. Additionally, or alternatively, the controller may also combine the sensed results for the plurality of expiratory portions and derive a combined expiratory sensed result.

The means 36 for determining the fan speed is one embodiment of a detection circuit for detecting the inhalation and exhalation portions of the user's breathing cycle. Another possible embodiment utilizes a pressure sensor as described above.

Fig. 2 shows an output 38 for providing output information to a user. The output 38 may be an integrated display, but is more preferably a wireless communication transmitter (or transceiver) for transmitting data to a remote device such as a smart phone, which may then be used as an end user interface for providing data to a user, and optionally for receiving control commands from the user for relay to the controller 30.

The fan 20 includes a fan blade 20a and a fan motor 20b. In one example, the fan motor 20b is an electronically commutated brushless motor, and the means for determining the rotational speed comprises an internal sensor of the motor. An electronically commutated brushless DC fan has an internal sensor that measures the position of the rotor and switches the current through the coils in such a way that the rotor rotates. Thus, internal sensors have been provided in such motors to enable feedback control of motor speed.

The motor may have an output port on which the internal sensor output 34 is disposed. Thus, there is a port carrying a signal suitable for determining the rotational speed.

Alternatively, the means for determining the rotational speed may comprise a circuit 36 for detecting ripple on a power supply connected to the motor 20 b. The ripple source is derived from the closing current through the motor coil, resulting in an induced change in the supply voltage due to the finite impedance of the battery 32. For example, the circuit 36 includes a high pass filter to process only signals in the frequency band in which the fan rotates. This provides a very simple additional circuit and is much less costly than conventional pressure sensors.

This means that the motor can be of any design, including a two-wire fan without built-in sensor output terminals. It will also work with DC motors with brushes.

If the outlet valve 22 is an electronically switched value, the breathing cycle timing information may be used to control the outlet valve 22 according to the phase of the breathing cycle.

In addition to controlling the outlet valve, the controller may also turn off the fan during inspiration or expiration. This gives the mask a different mode of operation and can thus be used to save power.

For a given drive level (i.e., voltage), the fan speed across the fan increases at a lower pressure as the load on the fan blades decreases. This results in enhanced flow. Thus, there is an inverse relationship between fan speed and pressure differential. This inverse relationship may be obtained during calibration or may be provided by the fan manufacturer. For example, the calibration process involves analyzing fan speed information over a period that instructs the subject to inhale and exhale regularly with normal breathing. Thereafter, the acquired fan speed information may be matched to the breathing cycle, and then a threshold value for distinguishing inhalation from exhalation is set accordingly.

Fig. 3A schematically shows rotor position (as measured sensor voltage) versus time.

The rotational speed may be measured from the frequency of the AC component of the DC voltage to the fan (caused by a switching event in the motor). The AC component results from a change in current drawn by the fan, which is applied to the impedance of the power supply.

Fig. 3A shows the signal during inspiration as curve 40 and the signal during expiration as curve 42. During exhalation, there is a decrease in frequency due to the increased load on the fan caused by the increased pressure gradient. Thus, the observed frequency variation is caused by different fan performance during the respiratory cycle.

Fig. 3B shows the frequency as a function of time by plotting fan speed versus time. There is a maximum difference in fan speed Δfan (Δfan) between consecutive maximum and minimum values, and this is related to depth of respiration. This is the first value derived from the fan rotation signal. The time between these points is used to derive a second value, for example the frequency corresponding to the time period (hence the frequency is twice the respiration rate).

Note that the first value may be obtained from the original fan rotation signal, or smoothing may be performed first. Thus, there are at least two different ways to calculate the maximum swing based on the untreated real-time speed or the treated speed. In practice, there is noise or other fluctuations added to the real-time signal. A smoothing algorithm may be used to process the real-time signal and calculate a first value from the smoothed signal.

During exhalation, the fan operates to force air out of the area between the face and mask. This improves comfort as exhalation becomes easier. This also draws additional air into the face, thereby reducing temperature and relative humidity. Between inspiration and expiration, fan operation increases comfort because fresh air is drawn into the space between the face and the mask, thereby cooling the space.

In one example, during inspiration, the outlet valve is closed (actively or passively), and the fan may be turned off to save power. This provides a mode of operation based on respiratory cycle detection.

If the fan is turned off during part of the breathing cycle and thus does not provide pressure information, the exact timing of the inspiration and expiration phases can be inferred from the previous breathing cycle.

For fan assisted exhalation, power needs to be restored before the outlet valve opens again. This also ensures that the next inspiration-expiration cycle remains in place and that sufficient pressure and flow is obtained.

Using this approach, power savings of approximately 30% can be easily achieved, thereby extending battery life. Alternatively, the power of the fan may be increased by 30% to improve efficiency.

Under different fan and valve configurations, the measurement of fan speed enables control to increase comfort.

In fan configurations where the filter is in series with the fan, pressure monitoring may be used to measure the flow resistance of the filter, especially based on the pressure drop across the fan and the filter. This may be done for a period of time after the mask has been turned on, but not yet worn on the face. This resistance can be used to represent the age of the filter.

As described above, fans using electronically commutated brushless DC motors have an internal sensor that measures the position of the rotor and switches the current through the coils in such a way that the rotor rotates.

Fig. 4 shows an H-bridge circuit, which acts as an inverter to generate an alternating voltage from the DC power supply VDD, GND to the stator coil 50 of the motor. The inverter has a set of switches S1 to S4 to generate an alternating voltage across the coil 50. The switches are controlled by signals that depend on the rotor position, and these rotor position signals can be used to monitor fan rotation.

Fig. 5 shows a general design of an optical particle sensor 24 that may be used as a sensor of the present invention.

There is a gas flow 60 from an inlet 61 to an outlet 62 of the entire sensor device. An infrared LED64 (λ=890 nm) is used to illuminate the gas stream to enable optical detection of entrained particles based on optical measurements of scattering. The LED is located on one side of the detection volume and the sensing is done on the opposite side. An alternative design may utilize reflection of light.

The optical sensor 66 includes a photodiode sensor 68 and a focusing lens 70 that collects scattered light.

The flow through the sensor device is provided by the respiration of the user. The air flow carries particles through the detection volume.

The controller 74 (which may be implemented as part of the controller 30) controls the processing of the sensor signals and the operation of the light sources.

The detection volume is for example part of a housing which is placed on a printed circuit board with electronics to convert the signals caused by the particles into counts. The internal shape of the housing minimizes leakage of LED light directly towards the photodiode light sensor, which leakage may create a background signal. By electronically filtering out any remaining dc signal, a pulsed particle signal is left.

The signal is amplified and compared to a threshold voltage. Above a certain particle size, the peak height is sufficient to exceed the threshold. Thus, the threshold value implements a band-pass filtering function. In one example of signal processing, pulses are counted and pulse lengths measured, resulting in a low pulse occupancy time (LPO%).

Thus, there are two basic outputs. One is a simple particle count, which is a count of the number of detected peaks that exceed a threshold set. The other is the proportion of time that is detected above the threshold. Thus, for a particular threshold level, if the total time the signal is at or above the threshold is 700ms within a 1s window, then the low pulse occupancy time is 70%. The low pulse occupancy measurement enables simple binary encoding of sensor output over time; for example, if the detected signal is above a threshold, a binary zero is output; if the detected signal is below the threshold, a binary 1 is output. The cumulative duration of the digital zero period corresponds to the low pulse occupation time. At this time, the combination time (per fixed unit of time) of the digital zero period is proportional to the analog output signal.

In this type of sensor, the amplitude of the analog signal is proportional to the particle size, whether particle counting or low pulse occupancy measurement is used. The threshold is realized as a threshold voltage applied to a comparator that controls the particle size sensitivity of the sensor system.

Larger particles scatter more light and thus generate a larger signal amplitude on the photodetector. The analog signal (after appropriate filtering and amplification stages) is provided to a comparator.

The threshold voltage provided to the comparator sets the boundary limit of the analog signal. For example, a threshold of 1V means that all signals greater than 1V will be registered as detection signals, and thus correspond to all particle sizes that generate analog signals above 1V. Also, the 2V threshold increases the boundary to allow only larger sized particles to produce output.

For simplicity, a threshold voltage of 1V may correspond to a signal generated for particles greater than or equal to 1 μm in diameter, while a threshold of 2V may correspond to particles greater than or equal to 2 μm in diameter.

The sensor may generate a count of individual particles (e.g., PM 2.5), or may apply different thresholds for different particle size ranges (also referred to as "size bins"). For example, for a particle size range between 1 μm and 2 μm, the number of signals generated at these threshold voltages is subtracted.

The sensor basically comprises:

a housing having an inlet and an outlet with a flow of gas therebetween;

a light source and an optical detector for performing optical scatterometry within the detection volume, wherein the detector signal is related (and e.g., proportional) to the particle size; and

and a signal processor for comparing the detector signal with a threshold value. The threshold may be fixed (for a single size detection function) or may be adjustable.

This is just one general example of an optical sensor. Other known optical sensor designs may also be used.

However, many such sensors require some time to produce a stable result. For example, the settling time of the PM2.5 sensor is known to be 10 seconds or longer. For Ultra Fine Particle (UFP) sensors this time may be even longer. The time required may also depend on the concentration of contamination, wherein the lower the concentration the longer the time required.

This delay in obtaining a stable signal is not due to physical limitations of the sensor, but rather because enough sample is needed to obtain a stable reading. The sensor generates data, for example, continuously, but requires some time before reliable results are given.

Fig. 6 shows the method of the invention in schematic form.

The graph shows a respiratory cycle wherein positive values represent exhalation and negative values represent inhalation. As described above, this may be measured by a differential pressure sensor or fan motor current.

Sampling windows are defined, such as window A, B, C representing an Expiration Phase (EP) and window X, Y, X representing an Inspiration Phase (IP).

The sensor is used to sample these data windows across multiple respiratory cycles in order to obtain enough data for a single reading from either the inspiratory portion or the expiratory portion. The number of respiratory cycles required depends on the duration of each respiratory cycle. For example, the faster breathing the more respiratory cycles are required.

In this way, enough samples are obtained for combining, defining (combined) readings of the individual sensors with sufficient accuracy. For example, by combining multiple samples from the inhalation cycle, the sensor may collect enough samples to create a measurement of inhaled air (after passing through the filter). Similarly, breath samples may be combined to give enough samples to create a measurement.

Depending on the flow to be analyzed, the sensor may detect only inhaled air or exhaled air.

One basic approach is to perform continuous monitoring and use post-processing to select the desired portion of the complete data stream. Since the final sensing result requires multiple respiratory cycles, the delay to wait for the complete data stream and perform the post-processing is not significant, e.g., a 10 second delay is not significant for generating the output.

However, real-time sensing may also be performed. The controller receives real-time sensed data from the sensor, for example. The amount of data is compared to a predefined threshold. The data may be used for pollution level calculation if the sampled data reaches a threshold, otherwise the data may be discarded.

Another approach is to perform sensing only during the sampling window. At other times between sampling windows, the sensor may be turned off, or the sensor may be physically exposed only during the intended portion of the cycle, with no sensor readings during other portions.

The preferred option is that the sensor samples continuously. The controller then determines which period of the sampled data is to be used to calculate the contamination level within the mask cavity based on the respiratory signal tracking (via the fan signal or the pressure sensor signal).

Fig. 7 shows three respiration waveforms. Fig. 7A shows breathing while sitting, fig. 7B shows breathing while walking, and fig. 7C shows breathing while running.

It can be seen that the user activity changes the breathing rate and depth.

Thus, the time window should be adapted to the breathing characteristics of the user. In particular, the time window should have the following width: such that the time window captures the main core portion of the inhalation or exhalation cycle, rather than being so wide as to overlap with the period of time that inhalation and exhalation are mixed. In particular, during the transition between the inspiration phase and the expiration phase, there is a mixture of inhaled air/exhaled air.

To this end, the system dynamically adjusts the sampling time based on changes in the respiratory cycle, particularly changes in the respiratory rate, for example in response to changes in user activity.

Even with the same general type of activity, the respiratory cycle of each individual is different. Thus, the sampling window may also be adjusted within the individual respiratory cycle in an even more dynamic manner.

Fig. 8 shows three respiration waveforms and a static threshold. Fig. 8A shows breathing while sitting with a first threshold, fig. 8B shows breathing while walking with a second threshold (below the first threshold, i.e. less negative), and fig. 8C shows breathing while running with a third threshold (below the second threshold, i.e. less negative).

The sampling period is shown as t1 to t12. The width is variable because the width corresponds to the time in each respiratory cycle that the signal (pressure or representative pressure) is below the threshold. Thus, the width depends on the time width of the actual breathing cycle.

Upon inhalation, once the user begins inhaling, the pressure within the cavity becomes negative. At the beginning of the inspiration phase, there is still some air in the cavity that the user had previously expired. The pressure is rapidly reduced and the particle sensor sampling start time may be set to the time at which the pressure reaches the negative threshold.

In the example of fig. 8, the threshold is predefined as a static value, which is typically the half-peak pressure value of the respiratory cycle. The half-peak pressure is only an example and other settings of the threshold may be used.

In another example, the threshold may be a self-setting dynamic value.

Fig. 9 shows three respiration waveforms and a dynamically self-adjusting threshold. Fig. 9A shows breathing while sitting, fig. 9B shows breathing while walking, and fig. 9C shows breathing while running.

The mask system records data of a previous breathing cycle or a previous set of breathing cycles, for example. The threshold may be set to half (or other fraction) of the peak pressure value of the previous respiratory cycle or a combination of previous respiratory cycle groups. In this way, the system can accommodate different activities, different users, and different effects caused by different amounts of leakage.

To ensure that the period of time during which the data is sampled is long enough, the controller maintains a timing count. For example, the controller starts a timer once the pressure drops below the threshold and stops the timer (i.e., measures the duration of the sampling periods t1 to t 12) once the pressure increases above the threshold.

Time periods are added from different cycles to form a total timing value. When the total timing value reaches the desired sampling time, the sensor has enough data to calculate a sensing result, such as a PM value.

The sensor needs to collect enough samples from the core period of the inspiration (or expiration) phase to determine the contamination value. For example, if the core period of the inspiratory phase (the phase of data is reliable) is 2 seconds and the sensor requires 10 seconds of data to derive a stable value, a total of 5 respiratory cycles will be combined to generate the sensor reading.

The mask may be used to cover only the nose and mouth (as shown in fig. 1), or may be a full face mask. The mask shown is a mask for filtering ambient air.

The mask designs described above have a primary air chamber formed by the filter material through which the user inhales air. Also as described above, an alternative mask design has a filter in series with the fan. In this case, the fan helps the user inhale air through the filter, thereby reducing the user's respiratory effort. The outlet valve enables exhaled air to be expelled and the inlet valve may be provided at the inlet.

The present invention may utilize the detected pressure changes caused by respiration to control the inlet valve and/or the outlet valve.

An option as described above is to use only a fan to draw air from inside the air chamber to the outside, for example when the exhaust valve is open. In this case, the pressure within the mask volume may be maintained below the external atmospheric pressure by the fan so that during exhalation there is a net flow of clean filtered air into the mask volume. Thus, the low pressure may be caused by the fan during exhalation, or by the user during inhalation (when the fan may be off).

An alternative is to use only a fan to draw air from the surrounding environment into the air chamber. In this case the fan is operated to increase the pressure within the air chamber, but in use the maximum pressure within the air chamber is kept below 4cmH2O higher than the pressure outside the air chamber, especially because high pressure assisted breathing is not envisaged. Therefore, a low power fan may be used.

Thus, it can be seen that the present invention can be applied to many different mask designs, with such fan assisted inhalation or exhalation, and with an air chamber formed by a filter membrane or with a sealed airtight air chamber.

In all cases, the pressure within the air chamber is preferably kept below 2cmH2O, or even below 1cmH2O or even below 0.5cmH2O above the external atmospheric pressure. Thus, the anti-contamination mask is not used to provide continuous positive airway pressure, nor is it a mask used to deliver therapy to a patient.

The mask is preferably battery powered, and therefore low power operation is of particular interest.

Fig. 10 illustrates a method of measuring particle or contamination levels within the air chamber of an anti-contamination mask.

Step 80 is an initialization step that includes setting a pressure threshold in step 80a, setting a desired (i.e., target) sensor sample time (typically 10 seconds) in step 80b, and setting a timer to zero in step 80 c.

The threshold pressure is used to determine when to begin sampling with the sensor and when to stop. The timer is used for recording the sensor sampling time.

In step 82, the user begins to use the mask and the system begins to sample the pressure, thereby tracking the user's breath.

In step 84, the sampled pressure is compared to a threshold pressure (Th) to determine if a steady portion of the breathing period has been reached within the inspiratory period (in this example).

If the pressure remains above the threshold, meaning that the breath has not reached the steady (core) period of the cycle, the method returns to step 82 (i.e., yes as shown) and pressure continues to be monitored.

When the pressure drops below the threshold (i.e., no as shown), this means that the sampling period of the particle sensor is reached.

The method then proceeds to step 86 where a timer is started to record the sampling period.

In step 88, the sensor is activated (or exposed to an air flow) to obtain sensed data such as particle counts.

In step 90, pressure continues to be monitored and sensing continues.

In step 92, the pressure is compared to a threshold pressure.

If the pressure is below the threshold, meaning that the breathing cycle is still in a steady period, the method returns to step 90 (i.e., no as shown) and the sensor continues to sample.

If the pressure is above the threshold, this means that the stable sampling period is over (i.e., the result shown is "yes"). The timer is then stopped in step 94. The time of the new record is the sampling time of the current cycle. However, the total sampling time is recorded by a timer.

Thus, steps 84-94 enable detection of the inspiratory portion of one respiratory cycle of the user and measurement of the sampling duration.

In step 96, the (total) time is compared with a set sampling period T (e.g., 10 seconds). If the desired total sampling time has not been reached (i.e., no result), it means that the particulate sensor data is not yet sufficient to obtain a reliable PM value. The method returns to step 82. The timer will then continue recording, i.e. the current timer value is used as the starting value for the next timing recording.

If the (total) time has reached or exceeded the sampling period T (yes result), it means that the sensor has enough data to calculate the PM value.

In step 98, a combined sensing result, such as a PM2.5 value, is obtained. The timer is then reset to zero in step 100 and the method returns to step 82.

By performing steps 82-96 multiple cycles, a combined sensing result is obtained for multiple inhalation (or exhalation) fractions.

Note that an alternative to the illustrated method is to continuously acquire sensor data, but to select an appropriate data sampling period using a method similar to that described above.

The mask may be supplemented with additional functionality and user interface options, but these are outside the scope of this disclosure.

As described above, embodiments utilize a controller to perform various desired functions, which may be implemented in software and/or hardware in a variety of ways. A processor is one example of a controller employing one or more microprocessors that may be programmed with software (e.g., microcode) to perform the desired functions. However, a controller may be implemented with or without a processor, and may also be implemented as a combination of special purpose hardware and processors (e.g., one or more programmed microprocessors and associated circuitry) that perform certain functions to perform other functions.

Examples of controller components that may be employed in embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application Specific Integrated Circuits (ASICs), and Field Programmable Gate Arrays (FPGAs).

In various implementations, the processor or controller may be associated with one or more storage media, such as volatile and non-volatile computer memory, such as RAM, PROM, EPROM and EEPROM. The storage medium may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform the desired functions. The various storage media may be fixed in the processor or controller or may be transportable such that the one or more programs stored therein are loaded into the processor or controller.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If the term "adapted" is used in the claims or specification, it should be noted that the term "adapted" is intended to be equivalent to the term "configured to". Any reference signs in the claims shall not be construed as limiting the scope.

Claims (15)

1. An anti-contamination mask comprising:

an outer wall (12), the outer wall (12) being adapted to define an air chamber (18) between the outer wall and a face of a user when the anti-pollution mask is worn;

-a filter (16) for forming a boundary between the air chamber and an ambient environment outside the air chamber;

a detection circuit for detecting an inhalation portion and an exhalation portion of the user's respiratory cycle;

A particle or contaminant sensor for sensing the interior of the air chamber and providing a sensing result;

a timer; and

a controller (30), the controller (30) being adapted to:

using the timer to time a combined duration of a plurality of inspiratory portions, combining sensed results from the detection circuit for the plurality of inspiratory portions to obtain sufficient data to derive a single combined inspiratory sensed result for a target combined duration without deriving an inspiratory sensed result for an individual inspiratory portion; or (b)

The combined duration of the plurality of expiratory portions is timed using the timer, and the sensed results from the detection circuit regarding the plurality of expiratory portions are combined so as to obtain sufficient data to derive a single combined expiratory sensed result for the target combined duration without deriving an expiratory sensed result for the individual expiratory portions.

2. The anti-contamination mask according to claim 1, wherein the detection circuit is to detect an inhalation portion and an exhalation portion based on a pressure inside the air chamber.

3. The anti-contamination mask according to claim 1, further comprising:

A fan (20) for drawing air from the outside of the air chamber (18) into the inside of the air chamber and/or drawing air from the inside of the air chamber to the outside of the air chamber.

4. The anti-contamination mask according to claim 3, wherein the detection circuit comprises:

a pressure sensor; or (b)

Means (34, 36) for determining the rotational speed of the fan, wherein the controller is further adapted to derive the pressure between the air chamber and the ambient environment from the rotational speed of the fan such that the fan speed is used as a representation of a pressure measurement.

5. The anti-pollution mask according to any one of claims 1-4, wherein the controller is further adapted to:

continuously collecting sensing results during a plurality of respiratory cycles; and

creating a subset of the sensing results related to the plurality of inspiratory portions to derive the combined inspiratory sensing result; and/or

A subset of the sensing results associated with the plurality of expiratory portions is created to derive the combined expiratory sensing result.

6. The anti-pollution mask according to any one of claims 1-4, wherein the controller is further adapted to:

Performing sensing at selected times corresponding to the plurality of inspiratory portions to derive the combined inspiratory sensing result; and/or

Sensing is performed at selected times corresponding to the plurality of exhalation portions to derive the combined exhalation sensing result.

7. The anti-pollution mask according to any one of claims 1-4, wherein the controller is further adapted to:

implementing a low pressure threshold below which the inspiratory portion is identified; and/or

A high pressure threshold is implemented above which the expiratory portion is identified.

8. The anti-contamination mask according to claim 7, wherein:

the low pressure threshold and/or the high pressure threshold are set according to a respiration rate; or (b)

The low pressure threshold and/or the high pressure threshold are dynamically adjusted based on the pressure within the air chamber during a previous inhalation portion and/or during an exhalation portion.

9. The anti-contamination mask according to any one of claims 1 to 4, wherein the particle or contaminant sensor comprises a light sensor based on light scattering.

10. The mask according to any one of claims 1-4, wherein the filter comprises an outer wall (16) of the air chamber.

11. A method of measuring a level of particulate or contamination within an air chamber of a contamination-resistant mask, the method comprising:

detecting an inspiratory portion and an expiratory portion of a user's respiratory cycle;

sensing a level of particulate or contamination within the air chamber of the anti-contamination mask; and

timing the combined duration of the plurality of inspiratory portions, combining the sensed results for the plurality of inspiratory portions so as to obtain sufficient data to derive a single combined inspiratory sensed result for the target combined duration without deriving an inspiratory sensed result for the individual inspiratory portion; or (b)

The combined durations of the plurality of expiratory portions are timed, and the sensed results for the plurality of expiratory portions are combined so as to obtain sufficient data to derive a single combined expiratory sensed result for the target combined duration without deriving an expiratory sensed result for the individual expiratory portions.

12. The method according to claim 11, comprising:

continuously collecting sensing results during a plurality of respiratory cycles; and

creating a subset of the sensing results related to the plurality of inspiratory portions to derive the combined inspiratory sensing result; and/or

A subset of the sensing results associated with the plurality of expiratory portions is created to derive the combined expiratory sensing result.

13. The method according to claim 11, comprising:

performing sensing at selected times corresponding to the plurality of inspiratory portions to derive the combined inspiratory sensing result; and/or

Sensing is performed at selected times corresponding to the plurality of exhalation portions to derive the combined exhalation sensing result.

14. The method according to any one of claims 11 to 13, comprising:

implementing a low pressure threshold below which the inspiratory portion is identified; and/or implementing a high pressure threshold above which the expiratory portion is identified.

15. The method according to claim 14, wherein:

the low pressure threshold and/or the high pressure threshold are set according to a respiration rate; or (b)

The low pressure threshold and/or the high pressure threshold are dynamically adjusted based on the pressure within the air chamber during a previous inhalation portion and/or during an exhalation portion.