Patent Description:
This document pertains generally to measuring airborne contaminants associated with a respiratory mask.

Emergency response personnel and military personnel use respirators for protection from airborne contaminants. Yet the effectiveness of these respirator depends not only on the quality of the filters employed, but also on the integrity of the fit of the respirator to the face of the user.

Technology for testing the fit of a respirator is inadequate.

<CIT> and <CIT> disclose prior art wearable devices for assessing the in-use effectiveness of respiratory masks.

The invention is directed to a wearable device for assessing the in-use effectiveness of a respiratory mask as defined in claim <NUM>.

In the next paragraphs a number of examples, not necessarily according to the invention, are given.

An example of the present user matter includes a dual-channel, ultrafine particle counter for in situ respirator fit testing. In situ respiratory fit testing is conduted with the respirator affixed to the user, and in some examples, this is referred to as on-person fit testing.

One example is directed to measuring the degree of protection from filterable, airborne contaminants afforded by a respirator mask while it is being worn by a user. One example assesses the fit of the mask on the user, as well as the effectiveness of the mask's filters. One example is a a wearable device configured to measure parameters while the user is physically active. One example measures and records selected indices of the user's activity level during respirator testing, thereby facilitating the study of the circumstances, or types of activities, that may degrade the respirator performance.

The quality of respirator fit may depend on the activity level of the user. An example of the present user matter is directed to evaluating the level of protection afforded by the mask in use. Such evaluation can be addressed through a wearable sensor.

One example includes a wearable device to assess the in-use effectiveness of the respirator mask. The degree of protection can be determined using a water-based condensation particle counter that measures the number concentration of airborne particles immediately outside the mask, and the concentration inside the mask, within the user's breathing area. These airborne particles act as a tracer for the amount of unfiltered air that penetrates the mask. A ratio of the number particle number concentration outside the mask to that inside the mask is called a "protection factor".

An example of the present user matter can be configured for measuring the number concentration of ultra fine, airborne particles, namely those with diameters ranging from approximately <NUM> to about <NUM>. These ultrafine particles are naturally highly abundant in the atmosphere. By enumerating their concentration immediately outside and inside of the respirator mask, it is possible to verify protection fitness factors as high as <NUM> over time periods of a few seconds, using ambient particles as the challenge. Thus, measurements can be done using ambient particles, without the need to generate a cloud of particles for testing.

Ultrafine airborne particles require condensational growth to enable their detection at the single particle level. One example of a condensation particle counter can detect ultrafine particles as small as <NUM>. One example of a commercially available condensation particle counter is designed for static testing, with the user seated and tethered to a desktop instrument. It is not suitable for measurements while the user is running, jumping, or otherwise physically active.

One example according to the invention includes a wearable, dual channel, water-based condensation particle counter configured to measure ultrafine particle concentrations both inside and outside of the respirator mask while the user is physically active. This example has two channels, permitting simultaneous measurement of particle concentrations inside and outside of the respirator mask.

One example of the present user matter includes an accelerometer to assess the activity level of the user during measurement. One example according to the invention incorporates a differential pressure sensor to detect the pressure drop across the mask, which is an indication of the nature and rate of the user's breathing. This example provides active flow monitoring of each of the two measurement channels. In one example, all these data are recorded in an on-board memory, with a common time stamp, so that leakage, when detected, can be correlated to the user's activity and breathing. Unlike the alcohol-based condensation particle counters of the prior art, one example of the present user matter uses a water-based condensation method, thus eliminating human exposure to this organic solvent, as well as the need for special supply item. Further, one example of the present user matter is battery powered, motion-tolerant, and compact. It can be mounted on the user's vest, belt or back pack. It may be worn by the user during measurement, enabling active, on-person measurement.

The present inventors have recognized, among other things, that a problem to be solved can include measuring respirator fit when worn by an active user. The present user matter can help provide a solution to this problem, such as by measuring particle counts both in the ambient environment and in the filtered-air environment under the respiratory mask as well as correlating particle count measuremnts with a measure of user actvity level.

This overview is intended to provide an overview of user matter of the present patent application.

An example of the present subject matter provides simultaneous measurement of ultrafine particle number concentrations in two channels, within a compact, battery operable, motion-tolerant instrument. The technical approach for ultrafine particle detection uses a motion-tolerant, water-based particle condensation method. One example of such a method is described in <CIT>), which in turn is based on the three-stage laminar flow water condensation technology described in <CIT>). It uses water, rather than alcohol, to add condensate to ultrafine particles to form optically detectable droplets. Additionally, water vapor is captured internally, thereby providing sustained operation without liquid replenishment, and without a liquid reservoir. Units based on this technology are impervious to jostling, shaking or orientation; a feature that results from the elimination of a liquid reservoir.

One example of the present subject matter includes a wearable respirator protection assessment system. One example is configured for respirator fit test measurements.

One example has two flow channels, one which samples from the airspace inside the respirator mask, and one that samples the ambient air immediately outside the mask. In one example, the user's breathing space inside of the respirator mask is accessed via the respirator drink tube. For example, particles can be measured using a flexible tube coupled to a drink tube port of the respirator.

The flow in each channel is configured to pass through a growth tube where ultrafine particles are enlarged through water condensation to form droplets which are subsequently counted by the optical detector. This provides simultaneous detection of ultrafine particles inside, and immediately outside of the mask.

A ratio between these two values represents a measure of the instantaneous protection afforded by the respirator mask. In one example, data are reported every second, yielding second-by-second readings of this protection factor.

In addition to these particle concentration measurements, one example of the present subject matter also monitors indicators of (<NUM>) how deeply and rapidly the user is breathing and (<NUM>) how much the user is moving. These factors can facilitate in investigation of the the efficacy of a respirator mask, as the fit can depend on the user activity. The user's breathing is indicated by the differential pressure sensor to detect the pressure drop across the mask, as illustrated in <FIG>. The filters through which the air passes create a pressure drop, and this pressure drop depends on the rate of that air flow. Thus, the pressure difference between the inside and outside of the mask fluctuates with each breath, and the extent of that fluctuation depends on how rapidly the user draws in air. Thus, this measurement indicates the nature and rate of the user's breathing. In one example of the present subject matter, this parameter is recorded at the rate of <NUM>, so that individual breaths can be tracked.

The user's motion and orientation can be monitored by the onboard accelerometer, which detects acceleration in each of three coordinates (x, y and z directions) at the rate of <NUM>. This data set is sufficient to determine if the user is still, walking, running, jumping, etc. All these data are recorded on-board, with a common time stamp, so that leakage, when detected, can be correlated to the user's activity and breathing.

One example of the present subject matter incorporates active flow monitoring of each of the two measurement channels. The flow exiting each optics head passes through a flow metering orifice, with pressure transducers that are calibrated to provide a reading of the flow in each channel. This provides active flow measurement in each of the two channels on <NUM>-sec time scales. This maintains accuracy in the particle concentration measurement, which is the ratio of counts to the volume of air sampled, should heavy breathing temporarily alter the flow split between channels. These measurements are illustrated in <FIG>.

One example of the present subject matter utilizes motion-tolerant particle condensation technology such as that in <CIT> in a dual channel water condensation growth tube and pair of miniature optical detectors, as shown in <FIG>.

The dual channel growth tube has three stages, each at separate temperatures, spanned by a continuous wick that transports water via capillary action among the stages. The first stage, referred to as the "conditioner", cools and humidifies the incoming flow. The second stage, called the "initiator", has warm, wet walls that add water vapor to the flow, thereby creating the supersaturation required to initiate condensational growth of ultrafine particles. The third stage, called the "moderator", cools the flow and recovers water vapor while maintaining supersaturated conditions. Water recovered within the conditioner and moderator stages is transported via capillary action to the initiator where it evaporates to create the supersaturation.

<FIG> illustrates some design aspects to enable miniaturization in a dual channel design. The three stages are seen by the blocks <NUM>, <NUM>, and <NUM>, while the optics heads 26A and 26B sit on top. The instrument uses three thermal electric devices, each operated as a heat pump with a common heat sink. The air flow 100cc/min per channel. The size of thermal electric devices, and the coupling between stages, can be tailored to reduce the power consumption. An optical detector can be a miniaturized version of a forward scattering detector. While the overall focal length was maintained, the width of each optics head can be reduced from <NUM> inches to <NUM> inches. The laser module can be configrued to allow the laser to allow alignment while both optical detectors are mounted in place, i.e. side by side. The electronics can be configured to include the laser control together with the photo diode detector electronics on a single board that mounts to the optics head. In one example, the optics are configured as a complete module, which can be easily replaced.

One example includes a folded circuit board to house selected components and the electronics in a compact package. The display and microprocessor chip are on one board mounted at the top of the instrument. This connects via an edge connector to the power board, which has micro-connectors for fans, temperature sensors, thermal electric devices, pumps, etc, as well as USB and power connectors. This allows a thinner and more ergonomic package.

Further size reduction can be achieved through careful placement of components, taking into account electrical cabling and pressure sensor connections. <FIG> is an internal view of one example in a case, showing the mounting of the internal components in its case. In this example, the power circuit board is along the left side, and connects to the display board at the top. A ribbon cable runs between the main board and the optics board. Various micro-connectors on the power board are mounted on the side to provide a straight run to the components.

<FIG> shows the outside view of one example of the present subject matter. The ventilation intake is on a front surface, and is protected by a low-efficiency filter. Ventilation flow exhausts out a bottom surface. The battery door is also on the front surface, and is easily accessible. A pigtail allows the battery to be swapped. A display is oriented on a top surface and remains visible when the device is installed in a pouch or while held by an operator. The assembled system is shown in <FIG>. The battery is accessible through the door on the outside of the case. The air intake is through the battery door, and includes a field-replaceable dust filter. The size is <NUM><NUM>, and the weight, with battery, is <NUM>.

The user interface is through the display (screen) and buttons mounted on the top of the unit, as shown in <FIG>. The software is menu driven, with up/down and enter and escape buttons for navigation. The power (on/off) button turns power on and off when depressed for more than <NUM> seconds, and otherwise acts as an escape to carry the user up one level in the menu. The user interface has a main screen and three subscreens, as listed in Table <NUM>. From the main screen the user may select "counts", which gives the option of "concentration" or "ratio". An example of a concentration screen is shown in <FIG>, and displays the number concentration measured by each channel. In this example both lines are sampling from the ambient air, and thus concentration readings are comparable. The ratio sub-screen displays the ratio in counts between these two channels, and is useful for examining the precision between the two channels (i.e. a ratio within <NUM>±<NUM>) or for looking at a real-time protection factor, calculated as a running <NUM>-sec ratio of the average ambient particle concentration divided by the average in-mask concentration. The <NUM>-second interval can be used for averaging, and in one example, is stored in a variable, and can be selectable through a laptop or from a screen.

The "fit test" screen allows the user to run a pre-programed fit test. The software can be configured to allow the test protocol to be programmed through a laptop connected to the instrument. The operator presses "enter" to start, and can terminate at any point by pressing "escape". In one example, the screen shows the Pass/Fail status and Protection Factor, at each step, and the cumulative (harmonic mean) Protection Factor at the end of the test. A summary screen displayed at the conclusion shows the protection factor at each step.

One example of the present subject matter includes an on-board data storage and Wi-Fi capability for storing and transmitting data in real time. The Wi-Fi channel sends data to a router, which then communicates to a laptop computer. These data is stored in a text file, and read via a suitable program (such as Python) to make these data readable by the laptop. The on-board storage includes a flash memory, and is downloaded to a laptop via a USB connection. In one example, both the Wi-Fi and flash memory data share the same file structure.

Measurement of Protection Factor entails measuring very low particle concentrations, in other words the false count must be low. This can be tested by operating the pair of of channels for an extended duration (such as overnight) with a filter on one line, while the other line samples ambient air. An example of results are shown in <FIG>. While the ambient particle concentrations fell in the range of <NUM>,<NUM>-<NUM>,<NUM>/cm<NUM>, the filtered air line yielded less than <NUM> count/hour. Even if this one count occurred during a <NUM>-s reading of the protection factor, the corresponding in-mask concentration would be <NUM>/cm<NUM>, and the indicated protection factor (at ambient concentration of <NUM>,<NUM>/cm<NUM>) would be <NUM>.

Laboratory test data with one example of the present subject matter is shown <FIG>. One sampling line can be connected to a respirator, and the other sampling ambient air, as would be done for assessing the protection factor. Shown are the acceleration, as measured by the on-board sensor, the number concentration in each channel as well as that from a nearby benchtop condensation particle counter, and the resulting protection factor (calculated as a <NUM>-sec running average). With the respirator in place, the protection factor indicated by the Level <NUM> system varied from <NUM> to <NUM>,<NUM>, with a mean of <NUM>,<NUM> while the user was standing, and <NUM>,<NUM> while the user was jumping. When the respirator was removed the protection factor was <NUM>, indicating measurement within <NUM>% of ambient particles by both channels.

<FIG> shows results for on-person testing, in which the respirator is mounted on a vest worn by a user. The results here can depict testing condcuted during Chemical Biological Operational Analysis (known as CBOA), with the user donning the mask midway through.

Accelerometer data in each of the x, y, and z axis are shown in <FIG>, which for this test was mostly small. The <NUM>-g reading on the one trace indicates gravity, and the orientation of the unit. Pressure differential data, that is the difference in air pressure from outside, and inside of the mask, is shown in <FIG>. In this example of <FIG>, the pressure difference is near zero until shortly after <NUM>:<NUM> AM, when the sujbect donned his respirator mask. Subsequent pressure variations, recorded at <NUM>, are due to the pressure drop, and over pressure, created by the user's breathing through the respirator. <FIG> shows the flow readings for each channel, which vary by <NUM>%, and these are mostly due to pulsations introduced by the pump, rather than from the users breathing. The data is corrected for these flow variations. <FIG> shows the <NUM> protection factor, calculated as the ratio outside/in-mask particle concentrations reported each second. When particle counts inside the mask are <NUM>, we assume a concentration corresponding <NUM> counts, as to prevent infinite protection factors. Before putting on the mask, reported protection factors are around <NUM>, indicating agreement between channels. With the mask, the protection factor was around <NUM>.

Data from later on in the same test as shown in <FIG>. The figure shows on-person testing conducted during CBOA, when a user wears the mask throughout.

Here, considerable variation is evident in the protection factor during the user's activities, with <NUM>-sec averaged values ranging from <NUM> to <NUM>,<NUM>. The plots, marked <FIG>, depict the type of data that can be obtained with one example of the present system. Further, the data shows that there is variability in the mask performance as it is worn.

One example of the present subject matter includes a wearable device to measure the protection afforded by a respirator while the user is physically active, through simultaneous measurement of the penetration of unfiltered air into the users breathing space, and further through simultaneous detection and recording of the user's activity level as indicated by breathing rate and accelerometer readings. In a miniaturized, battery-powered and wearable unit, the system couples measurement of the respirator protection factor simultaneously with measurement of key indicators of the users activity level. Further, one example uses water rather than alcohol to enable ultrafine particle detection, and combines two channels in a single unit. The wearable, dual channel, water-based, ultrafine particle counting, incorporating accelerometer sensor and inside/outside mask differential pressure sensor provides the opportunity to better understand in-use respirator fit and integrity.

In one example of the present subject matter uses two channels with each channel having separate growth tubes and separate optics. Unlike systems using a single channel and ports selected by a valve or switch, the two ports can be simulatneously measured. One example uses a common thermal unit (heating and cooling).

The processor of one example of the present subject matter can be configured to process the pressure signal from the differential pressure sensor and discern breathing rate and associated activity.

Wick materials can include Nylon, high-density polyethylene resin (HDPE), low-density polyethylene resin (LOPE), polyethylene, stainless steel, sintered material, ceramic, polyvinylidene fluoride (PVDF) , nitrocellulose, polytetrafluoroethylene (PTFE), or other hydrophilic material. The wick is fully wettable, designed to transport by capillary action, small pores (sub-micron), uniform pores.

Wick is wetted by distilled water or tap water. No reservoir required for make-up water - uses a self-sustaining water wick.

The above description includes references to the accompanying drawings, which form a part of the detailed description.

In the event of inconsistent usages between this document and any cited documents, the usage in this document controls.

" Also, in the following claims, the terms "including" and "coniprising" are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim.

Geometric terms, such as "parallel", "perpendicular", "round", or "square", are not intended to require absolute mathematical precision, unless the context indicates otherwise. Instead, such geometric terms allow for variations due to manufacturing or equivalent functions. For example, if an element is described as "round" or "generally round," a component that is not precisely circular (e.g., one that is slightly oblong or is a many-sided polygon) is still encompassed by this description.

Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or nonvolatile tangible computer-readable media, such as during execution or at other times.

Claim 1:
A wearable device for assessing the in-use effectiveness of a respiratory mask, the wearable device comprising:
a first condensation particle counter (26A) having a first inlet port, a first growth column, and a first optical element for counting particles detected at the first inlet port, the first condensation particle counter (26A) configured to provide a first signal corresponding to the particles counted at the first inlet port;
a second condensation particle counter (26B) having a second inlet port, a second growth column, and a second optical element for counting particles detected at the second inlet port, the second condensation particle counter (26B) configured to provide a second signal corresponding to the particles counted at the second inlet port;
wherein the first condensation particle counter (26A) and the second condensation particle counter (26B) are configured to include a wick in which the wick is wetted by water;
a differential pressure sensor coupled to the first inlet port and coupled to the second inlet port, the sensor configured to provide a pressure signal;
a processor coupled to memory and configured to receive the first signal, the second signal, and the pressure signal and generate an output corresponding to a ratio of the first signal and the second signal and correlate the ratio with the pressure signal; and
a housing configured to receive the first condensation particle counter (26A) and the second condensation particle counter (26B), the differential pressure sensor, the processor, and the memory.