Patent Publication Number: US-11644376-B2

Title: Directional differential pressure detector

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/078,041, filed Oct. 22, 2020, which claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Application Ser. No. 62/924,679, filed Oct. 22, 2019. The entire contents of these applications are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     Disclosed embodiments relate to methods and apparatuses for detecting the presence of a directional differential pressure. 
     DISCUSSION OF THE RELATED ART 
     Various applications within hospitals, laboratories, pharmaceutical facilities, clean room facilities, etc., often require a particular direction of air flow or differential pressure to be maintained, such as between neighboring rooms, compartments, corridors, ducts, or other spaces. The pressure of a room relative to adjacent space(s) will determine the net direction of air flow through an opening into or out of the room. 
     For example, a hospital operating room may be kept under a positive pressure so that air flows out of the room, thereby preventing unfiltered or contaminated air from entering the room from adjacent spaces. This positive pressure is accomplished by supplying clean air to the operating room at a greater flow rate than the flow rate at which air is exhausted from the room by the room&#39;s ventilation system. 
     Or, if a hospital patient is infected with an airborne communicable pathogen, a patient isolation room may be kept under a negative pressure which is accomplished when the rate at which potentially contaminated air is exhausted from the room is greater than the rate at which air is supplied to the room from the room&#39;s ventilation system. Such a negative pressure arrangement, where the room is under a comparatively lower pressure than its immediate surroundings, prevents potentially contaminated air from exiting the room and escaping into surrounding space(s). 
     The net differential pressure between rooms will cause air to flow through an opening from one room to the other in the direction from a higher pressure to a lower pressure. The desired degree of differential pressure to be maintained between rooms, compartments, corridors, etc. will vary, depending on the application. 
     Accordingly, it is often desirable to closely monitor the general direction of potential or actual air flow between compartments and in some cases the particular magnitude of differential pressure causing the net air flow. 
     SUMMARY 
     According to one embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate configured to mount the device to a first side of the barrier, and a first conduit portion configured to be in fluidic connection with the first space, the first conduit portion being configured to reach an opening in the first side of the barrier. At a location where the first conduit portion is configured to reach the first side of the barrier, an imaginary axis passes through a center of the first conduit portion, the imaginary axis being perpendicular to the baseplate. The device also includes a second conduit portion configured to be fluidically connected to the first conduit portion and the second space, where the second conduit portion is inclined at an angle relative to a horizontal plane when the baseplate is oriented vertically. The second conduit portion includes a movable element travel path section within which a movable element can travel, and the movable element travel path section has a longitudinal direction which is transverse to the imaginary axis. The device also includes a movable element disposed within the movable element travel path section and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The movable element travel path section has a first movable element stop and a second movable element stop, and the imaginary axis intersects the movable element travel path section at a location between the first movable element stop and the second movable element stop, and the imaginary axis does not intersect either of the first movable element stop and the second movable element stop. 
     According to another embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate configured to mount the device to a first side of the barrier, and a first conduit portion configured to be in fluidic connection with the first space, the first conduit portion being configured to reach an exterior opening in the first side of the barrier. At a location where the first conduit portion is configured to reach the first side of the barrier, an imaginary plane passes through a center of the first conduit portion, the imaginary plane being perpendicular to the baseplate. The device also includes a second conduit portion configured to be fluidically connected to the first conduit portion and the second space, where the second conduit portion is inclined at an angle relative to a horizontal plane when the baseplate is oriented vertically. The second conduit portion includes a movable element travel path section within which a movable element can travel, and the movable element travel path section has a longitudinal direction which is transverse to the imaginary plane. The device also includes a movable element disposed within the movable element travel path section and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The movable element travel path section has a first movable element stop and a second movable element stop, the first and second movable element stops being configured such that when the movable element is in contact with the first movable element stop, at least a portion of the movable element is positioned to a first side of the imaginary plane, and when the movable element is in contact with the second movable element stop, at least a portion the movable element is positioned to a second side of the imaginary plane, opposite to the first side of the imaginary vertical plane. 
     According to a further embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate and a first inclined conduit connected to the baseplate and configured to be fluidically connected to the first and second spaces. The first inclined conduit is connected to the baseplate with a first mounting portion, and the first inclined conduit is inclined at a first angle relative to a horizontal plane when the baseplate is oriented vertically. The first mounting portion is removable from the baseplate without damaging the baseplate or the first mounting portion. At least one movable element is disposed within the first inclined conduit and movable from a first, vertically lower region of the first inclined conduit to a second, vertically higher region of the first inclined conduit in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The device also includes a second mounting portion. When the first mounting portion is removed from the baseplate and the second mounting portion is connected to the baseplate, the second mounting portion is configured to hold an inclined conduit at a second angle, different from the first angle, relative to the horizontal plane when the baseplate is oriented vertically. 
     According to a further embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate and an inclined conduit connected to the baseplate and configured to be fluidically connected to the first and second spaces. The inclined conduit is inclined at an angle relative to a horizontal plane when the baseplate is oriented vertically. The device also includes a mounting portion which supports the inclined conduit, where the mounting portion is connected to the baseplate. The mounting portion includes a first locator, the baseplate includes a complementary second locator, and the first locator is configured to engage with the second locator to secure and orient the mounting portion at a desired roll orientation relative to the baseplate. Whenever the baseplate is secured to the barrier such that the baseplate is not rotatable relative to the barrier, and the mounting portion is secured to the baseplate, the angle of the inclined conduit relative to the horizontal plane is not adjustable without removing the mounting portion from the baseplate. The device also includes at least one movable element disposed within the inclined conduit and movable from a first, vertically lower region of the inclined conduit to a second, vertically higher region of the inclined conduit in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. 
     According to a further embodiment, device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate configured to be secured to the barrier such that the baseplate is not rotatable relative to the barrier, and an inclined conduit connected to the baseplate and configured to be fluidically connected to the first and second spaces. The inclined conduit is inclined at an angle relative to a horizontal plane when the baseplate is oriented vertically. While the baseplate is secured to the barrier such that the baseplate is not rotatable relative to the barrier, the angle of the inclined relative to the horizontal plane is not adjustable. The baseplate includes a plurality of baseplate mounting component sets configured to be aligned with a set of barrier mounting components. The baseplate mounting component sets are arranged such that the baseplate is securable to the barrier in a first roll orientation by aligning a first set of baseplate mounting components of the plurality of baseplate mounting component sets with a first barrier mounting component set, and securing the baseplate to the barrier using the first set of baseplate mounting components and the first set of barrier mounting components. The baseplate mounting component sets are arranged such that the baseplate is securable to the barrier in a second roll orientation, different from the first roll orientation, by aligning the first barrier mounting component set with a second baseplate mounting component set other than the first baseplate mounting component set, and securing the baseplate to the barrier using the first set of barrier mounting components and the second set of baseplate mounting components. The device also includes a roll indicator configured to indicate a threshold differential pressure set point when the baseplate is secured to the barrier in the first roll orientation and when the baseplate is secured to the barrier in the second roll orientation. At least one movable element is disposed within the inclined conduit and movable from a first, vertically lower region of the inclined conduit to a second, vertically higher region of the inclined conduit in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. 
     According to a further embodiment. a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a rotatable base configured to be rotatably attached to the barrier, and an inclined conduit coupled to the rotatable base. When the rotatable base is rotated, an inclination of the inclination conduit is adjusted relative to a horizontal plane. The inclined conduit has a longitudinal direction which is transverse to the rotatable base. The device also includes at least one movable element disposed within the inclined conduit and movable from a first, vertically lower region of the first conduit to a second, vertically higher region of the first conduit in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The device also includes a differential pressure set point indicator fixed to the rotatable base, where the differential pressure set point indicator includes a vial shaped in an arc and at least one movable marker disposed in the vial. 
     According to a further embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate configured to mount the device to the barrier, and a pivotable conduit connected to the baseplate and configured to be fluidically connected to the first space and the second space, where the pivotable conduit is pivotable about a pivot axis to be inclined at a plurality of angles relative to a horizontal plane. The device also includes a ball disposed within the pivotable conduit and movable from a first, vertically lower region of the pivotable conduit to a second, vertically higher region of the pivotable conduit in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The pivotable conduit includes a travel path for the ball, with a proximal end of the travel path being located at a first ball stop and a distal end of the travel path being located at a second ball stop. The first ball stop is positioned such that the ball intersects a longitudinal direction of the pivot axis when the ball is contacting the first ball stop, and the pivotable conduit is parallel to the barrier when the device is mounted to the barrier. 
     According to one embodiment, a device for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier is disclosed. The device includes a baseplate configured to mount the device to the barrier. A first conduit portion is configured to be in fluidic connection with the first space, where the first conduit portion is oriented to have a longitudinal direction which extends transversely to the barrier. A second conduit portion is configured to be fluidically connected to the first conduit portion and the second space, where the second conduit portion is inclined at an angle relative to a horizontal plane when the baseplate is oriented vertically, and the second conduit has a longitudinal direction which is transverse to the first conduit portion longitudinal direction. At least one movable element is disposed within the second conduit portion and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The second conduit portion forms a fluidic connection path which enters the second conduit in a direction transverse to a longitudinal direction of the second conduit, turns and travels in a direction away from the first conduit portion longitudinal direction, then turns and travels in a direction toward the first conduit portion longitudinal direction, passes the first conduit portion longitudinal direction, and travels away from the first conduit portion longitudinal direction toward an exit from the second conduit portion. 
     According to one embodiment, a device is provided for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier. The device includes a first conduit portion and a second conduit portion. The second conduit portion is fluidly connected to the first conduit portion and attached to a baseplate which is mountable to the barrier. The second conduit portion is inclined relative to the first conduit portion, and any rotation of the second conduit portion requires rotation of the baseplate. A roll orientation of the second conduit portion relative to the base is fixed. At least one movable element is disposed within the second conduit portion and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. 
     According to another embodiments, a device is provided for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier. The device includes a first conduit portion and a second conduit portion. The device further includes a mounting portion separated from the first conduit portion and configured to be connected to the first conduit portion such that the second conduit portion is fluidly connected to the first conduit portion. At least one movable element disposed within the second conduit portion and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. Once the mounting portion is connected to the first conduit portion, the mounting portion is not rotatable relative to the first conduit portion. 
     According to another embodiment, a device is provided for indicating a presence of a directional differential pressure between a first space and a second space separated from the first space by a barrier. The device includes a first conduit portion having a longitudinal axis, and a second conduit portion fluidly connected to the first conduit portion. At least one movable element disposed within the second conduit portion and movable from a first, vertically lower region of the second conduit portion to a second, vertically higher region of the second conduit portion in response to the directional differential pressure between the first and second spaces being greater than a threshold differential pressure. The second conduit portion has a travel path for the movable element, wherein the travel path extends transversely to an extension of the first conduit portion longitudinal axis and extends beyond the extension of the first conduit portion longitudinal axis in two opposite directions. 
     Advantages, novel features, and objects of the present disclosure will become apparent from the following detailed description of the present disclosure when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the present disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are not intended to be drawn to scale. In the drawings, some identical or nearly identical components that are illustrated in various figures are represented by a like numeral. Various embodiments of the present disclosure will now be described, by way of example, with reference to the accompanying drawings. The embodiments and drawings shown are not intended to narrowly define the present disclosure. In the drawings: 
         FIG.  1    is a front view of one embodiment of a device for indicating a directional differential pressure, the device being installed in a first orientation; 
         FIG.  2    is a front view of the embodiment of  FIG.  1    with the device installed in a second orientation. 
         FIG.  3    is a cross-sectional side view of the embodiment of  FIG.  1    in the installed orientation shown in  FIG.  1   ; 
         FIG.  4    is a cross-sectional side view of the embodiment of  FIG.  1    in the installed orientation shown in  FIG.  2   ; 
         FIG.  5 A  is a cross-sectional side view according to an alternative embodiment; 
         FIG.  5 B  is a cross-sectional side view of a conduit and conduit mounting portion which may be used with the device shown in  FIG.  5 A ; 
         FIG.  6    is a cross-sectional side view of an alternative embodiment; 
         FIG.  7    is a rear view of the embodiment of  FIG.  1   ; 
         FIG.  8    is a front view of an alternative embodiment; 
         FIG.  9    is a front view of an alternative embodiment; 
         FIG.  10    is a front view of another alternative embodiment where a conduit portion is rotatable relative to a baseplate; 
         FIG.  11    is a front view of another embodiment wherein a baseplate is adjustable across a continuous range of angles; 
         FIG.  12    shows the embodiment of  FIG.  10    with a photoelectric detector attached to the device; 
         FIG.  13    is a front view of an alternative embodiment; 
         FIG.  14    is a front view of an alternative embodiment with a rotatable base; 
         FIG.  15    is a top cross-sectional view of an alternative embodiment of a device for indicating a directional differential pressure; 
         FIG.  16    is a front view of an embodiment similar to the embodiment shown in  FIG.  15   ; 
         FIG.  17    is a top cross-sectional view of an alternative embodiment; and 
         FIG.  18    is a front view of the embodiment shown in  FIG.  17   ; 
         FIG.  19    is a cross-sectional side view of an alternative embodiment of a device for indication a directional differential pressure; 
         FIG.  20    is a top cross-sectional view of an alternative embodiment of a device for indicating a directional differential pressure; 
         FIG.  21    is a top cross-sectional view of an alternative embodiment of a device for indicating a directional differential pressure; 
         FIG.  22    is a top cross-sectional view of an alternative embodiment of a device for indicating a directional differential pressure; and 
         FIG.  23    is a top cross-sectional view of an alternative embodiment of a device for indicating a directional differential pressure 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to devices and systems which provide an indication of potential or actual directional air flow and/or whether a particular degree of directional differential pressure exists between spaces (e.g., two neighboring rooms or a room and an adjacent corridor) separated by a barrier such as a wall. In some embodiments, the device includes a first component located on a first side of a barrier, and a second component located on a second side of the barrier such that each component is subject to the air pressure within its respective space. The overall device is adapted to react to pressure differences between the two spaces to provide an indication to a viewer of the device. In some embodiments, the device may include sensors which communicate a status to a remote device, such as an alarm. 
     An air flow conduit may extend from one space to another space (e.g., room to hallway or hallway to a room that is separated by an anteroom between them). According to some embodiments, a visual indicator such as a lightweight ball or other movable element moves within the conduit in response to differences in air pressures between the two spaces. For example, in some embodiments, the air pressure in a room may be higher than in an adjacent hallway, and if the difference surpasses a threshold pressure, the movable element may move toward an end of the conduit to indicate the pressure difference exceeding the threshold. 
     An air flow conduit does not necessarily require that the conduit be arranged to permit air to be transferred from one space to another. Instead, the pressures on opposite sides of a wall may communicate without air flow moving all the way through the air flow conduit. For example, a conduit may pass from a hallway to a room, and a piston may be positioned with within the conduit. If pressure in the room is sufficiently higher than in the hallway to surpass a threshold pressure differential, the piston may move toward the hallway and be visible within the conduit in the hallway. If the piston is sealed within the interior of the conduit, no room air escapes into the hallway space, though a small amount of air flows behind the piston within the conduit. In this manner, the air flow conduit may provide a fluidic connection between two spaces where some minor air flow occurs within the conduit, yet no air is transmitted from one space to the other. 
     As discussed further below, in other embodiments, the fluidic connection may allow air to be transmitted between two spaces until a ball seats against an end of a conduit. In still further embodiments, air flows from one space to another even when a ball (or other movable element) reaches the end of its travel path. For purposes herein, when a first component is described as being fluidically connected to a space or to a second component, intermediate components may be present as part of the fluidic connection. 
     In some embodiments, a device for indicating a differential pressure between two spaces includes one or more conduits in communication with the air in both spaces such that a movable element disposed in the conduit(s) can react to directional air flow caused by the differential pressure. As described further herein, the conduit(s) may extend through the wall, or reside predominantly on one side of the wall, and adjustability of the incline of portions of the device may reside on a single side of the wall in some embodiments. The movable element (e.g., at least one ball) is disposed within a passageway of the conduit and moves freely back and forth along at least a portion of the length of the conduit. Restraints or end stops may be located at the ends or at other areas of the conduit to contain the ball within the conduit. The end stops may have openings that allow fluid (e.g., air, gas, liquid, water vapor, etc.) to flow through the passageway of the conduit from one end to an opposite end. 
     Systems are available for detecting whether a differential pressure between two spaces (e.g., between a clean room and an adjacent corridor) is above a threshold pressure difference. In some conventional systems, an inclined single conduit passes from one space to another through a wall, and a movable ball is placed in the conduit. On one side of the wall, for example the clean room side, the conduit has a lower region inside of the clean room and a higher region in the corridor. Gravity pulls the ball toward the lower region of the conduit. As the pressure in the clean room is raised higher than the corridor pressure, air pressure and/or air flow apply forces against the ball. Once the pressure difference between the clean room and the corridor reaches a threshold level, the force of the air against the ball overcomes the force of gravity, and the ball moves to a higher region of the conduit. By observing the presence of the ball in the higher region, a user can quickly see that the pressure difference between the two spaces equals or exceeds the desired directional differential pressure threshold level. To change the threshold pressure difference set point, the angle of inclination of the conduit is adjusted such that the amount of gravitational force on the ball in the direction of the conduit is adjusted. That is, in some embodiments, a greater incline of the conduit in which the ball travels requires a greater pressure differential between the two rooms to overcome gravity and move the ball from a lower to a higher region. 
     According to some embodiments of the present disclosure, a device is provided which provides for ease of installation. For example, in some embodiments, a differential pressure detector is arranged such that once the device is mounted to a barrier (e.g., a wall), an angle of inclination of a conduit portion is not adjustable. Further, the device may include a pitch indicator and/or a roll indicator to aid the installer in confirming the proper angle of inclination. In this manner, if a specific threshold pressure differential set point is desired, a simplified device can be installed with a conduit portion inclined such that the threshold pressure is set to the desired set point. In some embodiments, no further actions are required of the user, and potentially unwanted changes to the set point can be inhibited. For example, tampering with the set point may be discouraged with such an arrangement. 
     According to some embodiments, the combination of a roll indicator and a pitch indicator with a non-adjustable inclined conduit provides an arrangement which permits the installer and/or user to confirm that the device is set at a desired threshold pressure set point. For example, in such an arrangement, an installer can orient the baseplate until the roll indicator shows that the baseplate is at the desired roll orientation. The pitch indicator then may be used to confirm that the pitch of the inclined conduit is at the desired angle. With the roll at the desired orientation, the pitch indicator is useable to confirm the pitch of the inclined conduit. If the roll indicator were not present, and the roll orientation were not confirmed, the pitch indicator may not work in some embodiments. Or, in some embodiments, the pitch indicator may falsely indicate a correct pitch of the inclined conduit if the roll orientation is not actually at the desired orientation. In this manner, the combination of the roll indicator, pitch indicator, and non-adjustable incline conduit provides a device which may be correctly set to a threshold pressure set point without the need for extra equipment and/or burdensome calibration procedures. 
     According to some embodiments of the present disclosure, a viewer of the detector is able to check whether the device is calibrated. An out-of-calibration detector may result in the detector indicating a pressure differential which is not actually present, and the actual pressure differential may not meet minimum infection control or contamination standards. Applicant has recognized that it can be advantageous to have the detector arranged such that calibration can be performed using components which form part of the device such that external calibration instruments and/or procedures may be avoided in some embodiments. 
     Some embodiments of the device may be tamper-resistant in that once the device is installed, the inclination of the conduit portion which houses the movable element cannot be changed. Further, when installing the device in some embodiments, mounting the conduit portion at an incorrect inclination angle may be revealed by the pitch indicator and/or the roll indicator. 
     According to some embodiments, the above-described feature is provided by arranging a device to have a first conduit portion which is configured to pass through a wall, and a second conduit portion which is angled relative to the first conduit portion. The first and second conduit portions may be fixed to each other in such a manner (e.g., integrally formed) such that rotation of one portion rotates the other portion. In this manner, if the first portion is fixed to the wall such that the first portion cannot rotate, the inclination of the second portion relative to a horizontal plane remains fixed. For purposes herein, references to a “horizontal plane” refer to a plane which is perpendicular to the direction of the force of gravity. “Vertical plane” refers to a plane which is parallel to the direction of the force of gravity. 
     According to some embodiments, a conduit portion, within which a movable element travels, is inclined relative to the horizontal plane when the pitch indicator indicates that the device is at a desired pitch. For example, the pitch indicator may be a level, and when the level shows that the level is horizontal, the conduit potion may be inclined relative to the horizontal plane. 
     When mounting the device to a barrier, a baseplate may be used. If a barrier is not fully vertical, the baseplate may be shimmed or otherwise adjusted to orient the baseplate vertically. According to some embodiments, when the baseplate is oriented vertically, the conduit which holds the movable element is inclined relative to a horizontal plane. For purposes herein, a baseplate may be considered to be oriented vertically when its barrier-contacting surface has an orientation that the baseplate would have if it were to be placed against and secured to a smooth, vertical surface. That is, when referencing a “vertically oriented baseplate”, the orientation of the baseplate would be the same as when the baseplate is placed against and secured to a smooth, vertical surface. Referencing a vertically oriented baseplate to explain the inclination or orientation of another component does not require a baseplate to be vertically oriented or to be secured to a vertical barrier. 
     In some embodiments, a device is provided which can be installed to have a certain threshold pressure differential set point selected from among a discrete number of set points. For example, the device may have a choice of mounting holes in a baseplate such that the device is mountable to a wall at different roll angles. In such a device, once mounted, the device provides a certain threshold set point that is not adjustable without first at least removing the baseplate from the wall. 
     Turning to the figures,  FIGS.  1 - 4    shows one embodiment of a device  400  configured to be installed in either of two orientations. Device  400  includes a first conduit portion  402  which is configured to pass through at least a portion of a barrier  404 . A first end  406  of the first conduit portion  402  is attached to a first conduit support  408 , which in this embodiment is a cylinder with an internal diameter that accepts the external diameter of the first conduit portion. 
     A second conduit portion  410  is attached to a second conduit support  412 , which in this embodiment is a cylinder with an internal diameter that accepts the external diameter of the second conduit portion. The first and second conduit supports,  408 ,  412  are shown as being integrally formed with a baseplate  414 , though in other embodiments, one or both of the conduit supports may be separately formed and then attached to the baseplate  414 . 
     Second conduit portion  410  has a longitudinal axis  416  which is angled relative to a longitudinal axis  417  of first conduit support  408 . Longitudinal axis  417  may be coextensive with a longitudinal axis  418  of the first conduit portion  402 . With the first conduit support longitudinal axis  408  being horizontal in the illustrated embodiment, the longitudinal axis  416  of the second portion is inclined relative to a horizontal plane. Accordingly, in the orientation shown in  FIGS.  1  and  3   , to move a ball  420  (or other movable element) upwardly within the second conduit portion, the space on the right hand side of the barrier  404  will need to have a pressure that is higher than the pressure on the left hand side of the barrier. Additionally, to move the ball, the pressure difference between the two spaces will have to provide enough force on the ball to overcome the gravitational force on the ball. In this manner, the weight of the ball, the diameter of the ball, the inner diameter of the second conduit portion, and the incline of the second conduit portion establish a threshold pressure differential. 
     Two mounting holes  430 ,  432  are provided on the baseplate  414  to aid in mounting the device to a wall or other barrier. In the illustrated embodiment, the mounting holes are positioned 180° apart from each other and positioned relative to the second conduit such that the second conduit is pitched at the maximum angle relative a horizontal plane when the mounting holes are aligned vertically. Such an arrangement can ease installation by not requiring measurements or calibrations to be performed beyond confirming a suitable roll orientation and confirming that the device is plumb. 
     The illustrated embodiment may be installed in either of two orientations when the mounting holes are vertically aligned. In this manner, the device may be used to indicate positive pressure when mounted in a first orientation, or to indicate negative pressure when mounted in a second orientation. Other orientations are possible if the mounting holes are rotated to be not vertically aligned. However, installation procedures can be set forth in a straightforward manner to achieve a desired set point by manufacturing a device with second conduit portion which does not change in angle relative to the first conduit portion, and instructing the installer to align the mounting holes vertically using the on-board roll indicator. 
     In some embodiments, to maintain a constant angle between longitudinal axis  416  of second conduit portion  410  and longitudinal axis  417  of first conduit support  408 , conduit supports  412  and  408  are connected such that the supports are fixed relative to each other from an orientation standpoint. Conduit support  412  cannot be rotated relative to conduit support  408  in the illustrated embodiment. In this manner, once conduit support  412  is fixed to the wall via baseplate  414 , the angle of inclination is set and not adjustable without removing the baseplate. 
     In the illustrated embodiment, longitudinal axes  417  and  418  are horizontal, though in some embodiments, one or both of longitudinal axes  417  and  418  may be non-horizontal. Having longitudinal axis  418  be horizontal helps permit baseplate  414  to be oriented in either of two orientations that are 180° opposite to each other in a manner which allows second conduit portion  410  to have either of two opposite angles (e.g., +5° or −5°, or +15° and −15°). 
     According to some embodiments, the device includes a first level  434  and a second level  436  which are disposed on the baseplate  414  and are used to assist in mounting the rotatable base to a first side of the barrier to confirm that the second conduit portion is inclined at the correct angle. The second level  436  may be arranged in a direction transverse to the first side  10  of the barrier and may be configured to indicate whether the baseplate  414  is aligned with a vertical plane. When the baseplate is secured to the barrier, the second level also may indicate whether the barrier is out of plumb and not vertical. If the baseplate is not aligned with a vertical plane in the illustrated embodiment, the angle of inclination of the second conduit portion will not have the correct angle of inclination which establishes the threshold pressure differential set point. 
     An installer may set the correct threshold pressure set point by ensuring the second level  436  indicates alignment of a rear of the baseplate with a vertical plane. For example, if the wall is not plumb, the baseplate  414  may be shimmed or otherwise adjusted until the second level  436  shows that the device is correctly aligned. In one embodiment, the second level  436  may use an air bubble in liquid to indicate whether the device is oriented correctly, though other arrangements may be used. 
     In some embodiments, the second level may not need to be mounted to a baseplate surface. Instead, a different surface of the device may have second level  436  mounted thereon, and this different surface may be arranged such that when the surface is horizontal, the second conduit is set at a desired inclination with respect to the horizontal plane. 
     In some embodiments, the baseplate may not necessarily need to be aligned with a vertical plane to have the second conduit portion set to a correct angle. For example, the baseplate may be arranged to be oriented at an angle relative to a vertical plane, and other portions of the device may play a role in situating the device to a barrier. Second level  436  may still be used to indicate that a certain horizontal surface is horizontal to verify the desired inclination of the second conduit portion. By having a pitch indicator, such as second level  436 , attached to the overall device, ease of installation may be facilitated, and the confirmation of pitch may be checked periodically. 
     The first level  434  is configured to allow an installer to see whether a roll orientation of the baseplate  414  on the barrier is correct, and therefore the first level is oriented perpendicularly to the second level  436 . That is, the first level indicates when the baseplate is in a correct roll orientation relative to the barrier so that the roll orientation of the second conduit portion is at a desired orientation relative to a vertical plane. By incorporating a roll indicator on the device, ease of installation may be facilitated, and the roll orientation may be confirmed periodically. 
     A conduit cover  448  may be positioned over a second end  446  of the first conduit portion  402 . The conduit cover may include a collar  444  configured to receive the second end of the first conduit portion, and may further include air passageways  442  to allow for the flow of air through the device. 
     In some cases, devices of exemplary embodiments described herein may include a fire stop system that, upon the detection of a threshold level of smoke or fire, provides a barrier that blocks or otherwise mitigates travel of the smoke/fire from one space or room to another. The fire stop system may include various components used to seal the passage within the wall. For example, the fire stop system may include a fire stop ring  450  located on each side of the barrier. In some embodiments, there may be a single fire stop ring. The fire stop ring may include an intumescent substance that swells significantly as a result of heat exposure. The fire stop materials may be appropriately installed, for example, employing intumescent material as known to those of ordinary skill in the art. In some cases, the intumescent substance may produce char, which is a substance that acts to retard heat transfer. Devices of exemplary embodiments herein may be employed in fire-rated or non-fire-rated applications, as the present disclosure is not so limited. 
     The second conduit  410  may be transparent so as allowing viewing of the moveable element  420 . The second conduit support portion support  412  may be constructed with an opaque material so that the ball is not visible from the side of the device. In this manner, the presence or absence of the ball can be readily noticed to understand whether the threshold pressure differential is being met. The ball may be at least partially hidden or hidden by the support  412  from a side view of the conduit  410  and support  412 . 
     By hiding or at least partially hiding the ball in the second conduit portion support (e.g. a collar), it is not necessary for the ball to enter the wall or pass through the wall for the ball to be hidden. Accordingly, the first conduit portion may have a smaller diameter than the ball, which may reduce the size of the penetration that is made through the wall to install the device. For example, the ball may have a diameter of 1.5 inches, and the second conduit portion may have an inside diameter slightly larger than the ball. The first conduit portion may have an inner diameter of one inch, or half an inch, or any other suitable inner diameter that is smaller than the diameter of the ball. 
     The embodiment illustrated in  FIG.  5 A  shows a second conduit portion  460  and a second conduit portion support  462  which are separable from a baseplate  464 . The second conduit portion support  462  may include a mounting portion  473 , which may be circular, with snap-fit connectors  471 ,  472  for attachment of the assembly to the baseplate  464 . The baseplate may include notches configured to receive snap-fit connectors  471 ,  472  such that the second conduit portion assembly is attachable in the baseplate in only two orientations. In this manner, the second conduit portion assembly may be set at a positive incline or a negative. In other embodiments, the snap-fit connectors  471 ,  472  and the baseplate may be arranged such that the second conduit portion assembly can be attached to the baseplate in only one orientation. The interaction between the snap-fit connectors and the notches may prevent rotation of the second conduit portion assembly once the assembly is attached to the baseplate. In this manner, tampering or accidental movement of the second conduit portion may be inhibited. 
     The snap-fit connectors  471 ,  472  may act as locators to orient the mounting portion  473  in a desired roll orientation relative to the baseplate. The associated notches in the baseplate may serve as complementary locators on the baseplate to receive the locators which are positioned on the mounting portion  473 . Other suitable locators may be used. 
     In some embodiments, conduit mounting portion  473  and baseplate  464  may be constructed such that the conduit mounting portion is removable from the baseplate without damaging the conduit mounting portion or the baseplate. For example, a user may squeeze the members holding snap-fit connectors  471 ,  472  toward one another to remove the conduit mounting portion from the baseplate. Such an arrangement may permit installation and/or removal of the conduit mounting portion without the use of a tool. In some embodiments, a tool may be used to attach and/or detach the conduit mounting portion to the baseplate. 
     In some embodiments, mounting portion  473  may have a geometry other than circular. For example, mounting portion may be square, thereby preventing rotation once the mounting portion is attached to the baseplate  464 . In the case of a square, in some embodiments the second conduit portion may be mounted in one of four different roll orientations. In other embodiments, a triangle or other shapes may be used. 
     In some embodiments, the conduit mounting portion shown in  FIG.  5 A  may be arranged to hold the inclined conduit such that the inclined conduit is parallel to the baseplate and/or barrier. 
     The embodiment illustrated in  FIG.  5 B  shows a second conduit portion  460  and the mounting portion  473  as a single piece. In some embodiments, the second conduit portion  460  and the mounting portion  473  may be integrally formed. The mounting portion  473  of  FIG.  5 B  may be configured to hold second conduit portion  460  at a different inclination relative to the horizontal plane when installed as compared to the second conduit portion shown in  FIG.  5 A . In this manner, a user may be able to swap mounting portions to attain a different angle of inclination. In some embodiments, the same second conduit portion may be used with both mounting portions. In some embodiments, a different second conduit portion may be used with each conduit mounting portion. A portion of the second conduit  460  in the embodiment of  FIG.  5 B  may be opaque, while another portion may be transparent. 
     A telescoping first conduit portion  475  is also shown in  FIG.  5 A . Two pieces  476 ,  477  are slidable relative to one another to allow for adjustment in length. In some embodiments, once the two pieces  476 ,  477  and arranged to form a first conduit portion of a desired length, the pieces may be adhered to another and adhered to first and second collars  478 ,  479 . In other embodiments, only some or none of the pieces may be permanently attached, and the mounting of baseplate  464  and conduit cover  480  to the barrier may serve to hold the conduit portion pieces  476 ,  477  in place. 
     The second conduit portion support  412  may be constructed with an opaque material so that the ball is not visible from the side of the device. In this manner, the presence or absence of the ball can be readily noticed to understand whether the threshold pressure differential is being met. 
     A ramp  490  may be positioned around the circumference of an inside of an end cap on second conduit portion  460  to aid in seating the ball  470  against a hole in the end cap. In this manner, the ball may seal (or reduce) air flow through the second conduit portion when the ball is pushed against the end cap. The ramp  490  may be positioned around the entire inner circumference of the second conduit portion, or the ramp may be present in select areas. For example, if the second conduit is rotatable only to certain roll angles, the ramp may only be present in certain arcs of the inner portion of the second conduit portion which correspond to where the ball will be traveling at those roll angles. 
     By hiding or at least partially hiding the ball in the second conduit portion support (e.g. a collar), it is not necessary for the ball to enter the wall or pass through the wall for the ball to be hidden. Accordingly, the first conduit portion may have a smaller (or larger) diameter than the ball, which, when smaller, may reduce the size of the penetration that is made through the wall to install the device. For example, the ball may have a diameter of 1.5 inches, and the second conduit portion may have an inside diameter slightly larger than the ball. The first conduit portion may have an inner diameter of one inch, or half an inch, or any other suitable inner diameter that is smaller than the diameter of the ball. 
     The embodiment illustrated in  FIG.  6    includes device  500  which is similar to device  400  shown in  FIGS.  1 - 4   . A pitch level  536  is shown in an alternative position as compared to the embodiments of  FIGS.  1 - 4   . In this embodiment, the pitch level  536  is mounted on a side of a conduit support  512 . 
     A detector such as a photoelectric sensor  550  may be employed to detect the presence and/or absence of the movable element, such as a ball  520 . In the illustrated embodiment, when the ball returns to a lower vertical region, as shown in  FIG.  6   , thereby indicating the differential pressure that is below the threshold differential pressure, photoelectric sensor  550  detects the presence of the ball and sends a signal. The detector may transmit the signal to trigger an alarm or annunciator to alert someone that the differential pressure is below the threshold. In some systems, the detector may transmit a signal to a controller such as an HVAC controller or a building services controller. 
     As shown in  FIG.  6   , the device  500  also includes a transparent shield  530  which may be used to protect the second conduit portion and other components from unintentional contact while allowing the movable element to remain visible so that a differential pressure may be indicated. The shield includes an orifice  532  which allows air to pass from the first side of the barrier to the second conduit portion through an end stop  518 . Accordingly, the shield does not interfere with the differential pressure based movement of a movable element in the second conduit portion. It should be noted that the shield may be omitted from the device  500  without a corresponding loss in functionality of the device and/or movable element disposed therein. 
     The embodiments shown in  FIGS.  1 - 6    allow an installer to adjust the length of the device to conform to the thickness of the wall or other barrier when installing the device to a wall or other barrier. For example, the first conduit portion  402  may be telescoping or may be a continuous tube which is cut to size and then inserted into first conduit support  408  and collar  444  of the rear cover so that the device fits in a particular barrier. In prior devices with a single, straight conduit portion that penetrates through both sides of a wall and allows the ball to travel through the wall, the thickness of the wall would typically need to be known before manufacture of the device. Cutting can lead to particles entering the conduit, and therefore in prior devices, cutting a conduit that acts as a full passageway for the ball could lead to particles which obstruct the travel of the ball. In some embodiments disclosed herein, separate conduit portions are used, and the ball travels only in the one of the portions. The other portion (e.g., the portion that travels through the wall) can be cut and cleaned, and then attached to the conduit support without affecting the conduit portion through which the ball travels. 
       FIG.  6    shows an embodiment where a conduit portion traveling through at least a portion of the wall has a smaller diameter than the conduit portion which contains the movable ball  520 . 
       FIG.  7    shows conduit cover  448  from a viewpoint toward the outside of the barrier to which the conduit cover is attached. The conduit cover includes their passageways  442 , which may be sized and shaped in any suitable configuration. Mount holes  454 ,  456  may be included. 
       FIG.  8    shows an embodiment where a baseplate  714  is mountable in any one of four discrete roll orientations, although more or fewer discrete roll orientations may be used. A second conduit portion  710  remains fixed in its inclination once the baseplate  714  is secured to the wall. In this manner, different inclinations of the second conduit portion  710  are available to the installer. Accordingly, four different threshold pressure differentials are achievable with this single device. In the orientation illustrated in  FIG.  8   , the maximum downward inclination achievable with this particular embodiment is shown. Rotating the baseplate  714  clockwise to vertically align mounting holes  734  and  736  will rotate second conduit portion  710  clockwise and thereby decrease the downward angle of the second conduit portion. In this embodiment, the second conduit portion is not rotatable relative to the baseplate. As such, the threshold pressure is not adjustable unless the baseplate is uninstalled, repositioned, and reinstalled. 
     The embodiment illustrated in  FIG.  8    includes four sets of baseplate mounting components: a first set including mounting holes  730 ,  732 ; a second set including mounting holes  734 ,  736 ; a third set including mounting holes  738 ,  740 ; and a fourth set including mounting holes  742 ,  744 . While the sets of mounting holes shown in  FIG.  8    include two mounting holes, a set may include at least two mounting holes, three or more mounting holes, or any suitable number of mounting holes. 
     A roll level  731  may be used to confirm that mounting holes  730 ,  732  are vertically aligned. Additional roll levels may be mounted on the baseplate adjacent to mounting holes  736 ,  740 , and  744  so that vertical alignment of those mounting holes may be confirmed when the device is installed in the different roll orientations. Markings  746  indicating threshold pressure differentials associated with each orientation may be included directly on the baseplate. A pitch level  733  may be mounted to the baseplate and/or to a conduit support  712 . A photoelectric detector  750  may be included to detect the presence and/or absence of a ball or other movable element within the second conduit portion. 
     Mounting holes  730 ,  734 ,  738 , and  742  may all have a same radial distance from the center of the baseplate. Mounting holes  732 ,  736 ,  740 , and  744  may all have a same radial distance from the center of the baseplate. Though the radial distance of mounting holes  732 ,  736 ,  740 , and  744  may differ from the radial distance of mounting holes  730 ,  734 ,  738 , and  742 . 
     Other types of mounting components may be used as baseplate mounting components and/or barrier mounting components. For example, the baseplate may have resilient plugs which can be pushed into receptors adhered to the barrier 
       FIG.  9    illustrates an alternative embodiment of a baseplate  800  in which instead of mounting holes, mounting slots  802 ,  804  are provided. In this manner the orientation of the baseplate continuously varied across a given range. 
     As with other embodiments disclosed herein, the roll orientation of the second conduit portion relative to the baseplate may be fixed. A vial  806  with a weighted ball  808 , or a gas bubble  814  or other pointer may be included on the baseplate to indicate the threshold pressure differential set point associated with the installed roll orientation of the baseplate. For example, threshold pressure differential values may be marked along the length of vial  806 . Other suitable markings may be used in other embodiments. Any suitable device may be used to indicate the roll angle and/or threshold pressure differential set point. For example, a device which responds to the force of gravity (e.g., bubble inclinometer, pendulum inclinometer, etc.) may be mounted to an appropriate portion of the baseplate so that an accurate determination can be made as to the actual degree of roll of the baseplate. 
     A photoelectric detector  850  or other detector may be used to sense the presence and/or absence of a movable element within a second conduit portion  810 . 
       FIG.  10    is a front view of another embodiment of a device  100  for indicating a directional differential pressure. The embodiment of  FIG.  10    is configured to indicate a threshold differential pressure set point based on the angle of inclination of a pivot arm  116  relative to a horizontal plane. That is, in the depicted embodiment, the pivot arm  110  includes a rotatable base  140  which rotates concurrently with the pivot arm. The rotatable base includes an arrow  144  which is aligned with an end of the pivot arm which is inclined as the pivot arm rotates. Pluralities of markings  142  are disposed on a baseplate  102  which is fixed to the wall. The markings are disposed around a circumference of the rotatable base in a predetermined interval and denote various angles of the pivot arm. The markings may correspond to threshold differential pressure set point values from a separate chart or may list threshold differential pressure set point values. Thus, during installation of the device, the pivot arm may be rotated to a position so that an appropriate differential pressure threshold may be set for a given space. The accuracy of the markings  142  may be affected by the alignment of the pivot arm axis of rotation with a horizontal plane, which may be indicated with a first level  120 . Additionally, the accuracy may also be partly determined by the roll orientation of the rotatable base  102 , the correct orientation of which is indicated by a second level  122 . Together, the pitch indicator  120  and the roll indicator  122  may be used to calibrate the correct orientation of the device so the markings and pointer may be calibrated. A photoelectric detector  950  and/or other detector may be employed to detect the presence and/or absence of a ball  200  within pivot arm  116 . Mounting holes  103  may be provided at any suitable locations to mount baseplate  102  to the wall. Shims may be used along with the plumb level  120  to set the base  102  plumb, and thus set a horizontal axis of rotation for pivot arm  110 . 
       FIG.  11    illustrates an embodiment where a device  1000  includes a second conduit portion  1016  which is rotationally fixed to a baseplate  1014 . In this manner, the inclination of the second conduit portion  1016  is not adjustable relative to the baseplate. The inclination of the second conduit portion can be changed by loosening mounting fasteners  1020 ,  1022 , rotating mounting slots  1002 ,  1004  about the fasteners, and tightening mounting fasteners  1022 ,  1024 . 
     A curved vial  1006  with a weighted ball  1008  or other suitable pointer may be used indicate the roll angle and/or the threshold pressure differential set point brought about by the roll angle of the baseplate. The vial may include a liquid and a gas bubble. A pitch level  1030  may be included to help installation of the device such that the baseplate  1014  is vertically aligned. Together, the pitch indicator  1030  and the roll indicator  1006  are used to calibrate the correct orientation of the device so that the inclination angle of the second conduit  1016  may be calibrated. 
       FIG.  12    shows an embodiment similar to the embodiment of  FIG.  11   , and additionally includes a photoelectric sensor  1150  or other sensor to sense the presence and/or absence of a ball  1120 . 
       FIG.  13    shows an embodiment of a device  1200  which is similar to the embodiments illustrated in  FIGS.  11  and  12    in several respects, but has a second conduit portion  1210  which is not parallel to the barrier. In this embodiment, the second conduit portion  1210  has a yaw rotation relative to baseplate  1214 . As such, a ball in the transparent portion of the second conduit portion  1210  may be viewable from the side of the device and the front of the device. As discussed above regarding various embodiments, a plurality of mounting holes  1230  may be provided to permit mounting of the device in a plurality of roll orientations. In some embodiments, the device may provide fewer discrete mounting orientations, for example, only one orientation or only two mounting orientations. A weighted ball  1208  may held within a curved vial  1206  to associate a mounted orientation with markings  1240  to indicate the threshold differential pressure set point. A photoelectric sensor  1250  or other sensor may be included to sense the presence and/or absence of a ball. 
       FIG.  14    shows an embodiment of a device  1300 , which, similar to the embodiment of  FIG.  13   , includes a second conduit portion  1310  that is rotated away from the baseplate so that a side of the transparent portion of the second conduit portion  1310  is visible both from the side of the device and from the front of the device. 
     In the embodiment of  FIG.  14   , the second conduit  1310  is mounted to a rotatable base  1338  which is rotatable relative to a baseplate  1314 . In this manner, the second conduit portion  1310  can be rotated continuously along a range of roll angles. A weighted ball  1308  may held within a curved vial  1306  to associate a mounted orientation with markings  1340  to indicate the threshold differential pressure set point. A photoelectric sensor  1350  or other sensor may be included to sense the presence and/or absence of a ball. A lock, such as a rotating tab  1311 , may be used to hold the rotating base against rotating. 
       FIG.  15    shows an embodiment of a threshold directional differential pressure indicator configured to provide a reduced radial extent of a second conduit portion  1110  from a rotation axis of the second conduit portion as compared to some arrangements where a second conduit portion is attached to a baseplate with a single ninety degree bend. In the orientation illustrated in  FIG.  15   , an airflow path  1109  between a first conduit portion  1102  and the second conduit portion  1110  travels in a first lateral direction upon exiting the first conduit toward the second conduit, and then turns and travels in a second lateral direction within the second conduit portion. This arrangement allows the second conduit portion to be positioned farther to the left (from the viewpoint of  FIG.  15   ) as compared to an arrangement where the airflow path exits the first conduit portion and makes a single turn into the second conduit portion. In some embodiments, portion  1103  may be considered to be part of a first conduit portion, or in some embodiments may be an entirety of a first conduit portion. 
     The embodiment illustrated in  FIG.  15    allows the device threshold differential pressure set points to be adjustable after the baseplate is secured to the barrier. 
     In some embodiments, a movable element such as a ball  1120  travels along a travel path, such as a travel path  1115 , which is located in a travel path section  1116  of the second conduit. When the ball travels toward the opening of conduit  1110  closest to the fluid path of the first space (e.g., a proximal end of the travel path section), a ball stop, such as an end stop  1130  stops the ball from leaving second conduit  1110 . End stop  1130  has an opening for fluidic communication between the first space and the second space. When the ball travels toward the opening of second conduit portion  1110  closest to the fluid path of the second space (e.g., toward a distal end of the travel path section), a ball stop, such as an end stop  1140  stops the ball from leaving second conduit  1110 . End stop  1140  has an opening for fluidic communication between the first space and the second space. When the ball is located next to end stop  1140 , the transparent conduit  1110  allows a viewer to see the ball. When the ball travels at least one ball diameter towards end stop  1130 , conduit wall  1145  of the second conduit portion may be opaque and the ball is no longer visible from the side of conduit  1110 . 
     In some embodiments, the travel path length may be one and a half ball diameters, two or more ball diameters, or any suitable length. Proximal end stop  1130  may be located on an opposite side of a rotation axis  1117  as distal end stop  1140 . A plenum portion  1150  may be provided in second conduit portion  1110  and provide at least part of a fluidic connection between the first conduit portion  1102  and the second conduit portion  1110 . 
     When the travel path starts at a lateral position which is at or near the lateral position of a rotation axis  1117  of the second conduit portion  1110 , the second conduit extends radially by approximately the length of the second conduit portion (when the second conduit portion is parallel to the wall). By shifting the second conduit portion, the travel path  1115  of the ball  1120  crosses the location of rotation axis  1117 , and reduces the lateral extent of the second conduit portion from the rotation axis, which may be the approximate center of the device in the front view. In this manner, a suitable travel length for the movable element may be provided while reducing the radial extent of the device. 
     The pathway between the first and second spaces may be configured such that the fluid (e.g., air) path adjacent to an entrance to a proximal end of the travel path section is substantially aligned with the direction of travel path  1115 . 
       FIG.  16    shows a front view of an embodiment similar to the embodiment of  FIG.  15   . In the embodiment of  FIG.  16   , the second conduit portion  1110  is attached to a rotatable base  1121  which rotates relative to a baseplate  1114 , the baseplate being fixed to the wall. A pointer  1125  on rotatable base  1121  may be arranged to point to markings  1127  on the baseplate  1114 . Pluralities of markings  1127  may be disposed on a baseplate  1114  which is fixed to the wall. The markings may be disposed around a circumference of the rotatable base  1121  at predetermined intervals and may denote various inclination angles of the second conduit  1110 . The markings may correspond to threshold differential pressure set point values shown on a separate chart, or the markings may directly display threshold differential pressure set point values. During installation of the device, the rotatable base  1121  may be rotated to an orientation such that a desired differential pressure threshold may be set for a given space. The accuracy of the markings  1127  may be affected by the alignment of the rotating base  1121  axis of rotation with a horizontal plane. Whether the axis of rotation is aligned as desired may be indicated with a first level  1129 . Additionally, the accuracy may also be partly determined by the roll orientation of the baseplate  1127 . Whether the roll orientation is at a desired angle may be indicated by a second level  1131 . Together, the pitch indicator  1129  and the roll indicator  1131  may be used to calibrate the orientation of the device so the markings and pointer provide accurate readings. A photoelectric detector  950  and/or other detector may be employed to detect the presence and/or absence of a ball. Shims may be used along with the pitch level  1129  to set the baseplate  1114  plumb, and thus set a horizontal axis of rotation for rotatable base  1121 . 
     A pitch level  1129  and/or a roll level  1131  may be included on the device to facilitate an accurate installation of the device, and to confirm continued alignment of the device over time. 
       FIGS.  17  and  18    show an embodiment of a threshold directional differential pressure indicator configured to provide a reduced radial extent of a second conduit portion  1110 . The illustrated embodiment allows the device threshold differential pressure set points to be adjustable when the baseplate is loosely mounted and then becomes non-adjustable after the baseplate is secured to the barrier. The embodiment of  FIGS.  17  and  18    are similar to the embodiment illustrated in  FIGS.  15  and  16   , but instead of including a rotatable base, the embodiment of  FIGS.  17  and  18    includes mounting slots  1702 ,  1704  in the baseplate. In this manner the roll orientation of the baseplate may be continuously varied across a given range prior to securing the baseplate to the barrier. 
     A weighted ball  1708  may held within a curved vial  1706  to associate a mounted orientation with markings  1740  to indicate the set point. A photoelectric sensor  1750  or other sensor may be included to sense the presence and/or absence of a ball. 
     An imaginary axis  1720  may be oriented to be perpendicular to the baseplate, and oriented to extend through a center of the first conduit portion  1712 . A travel path section  1716  of the second conduit portion  1710  may be positioned such that imaginary axis  1720  intersects travel path section  1716  between a proximal ball stop and a distal ball stop, such as proximal end stop  1730  and distal end stop  1740 . And as shown in  FIG.  17   , the imaginary axis does not intersect either of the proximal ball stop and the distal ball in some embodiments. In some embodiments, travel path section  1716  of the second conduit portion  1710  may be positioned such that when ball  1120  is contacting a proximal ball stop such as end stop  1730 , at least a portion of the ball may travel past imaginary axis  1720 . In some embodiments, the entire ball may be positioned on a first side of the imaginary axis when in contact with proximal end stop  1730 , and the entire ball may be positioned on second, opposite side of the imaginary axis when in contact with distal end stop  1740 . In some embodiments, the imaginary axis intersects the travel path section  1720  at a middle of travel path section  1720 . In some embodiments, the travel path section is oriented parallel to the baseplate, though in some embodiments (see  FIG.  23    for example), the travel path section may be oriented transverse to the baseplate. In some embodiments, the imaginary axis intersects the second conduit portion in the middle of a side-to-side extent of the second conduit axis. For example, the second conduit portion may have a radial extent to one side of the imaginary axis which is the same as the radial extent on an opposite side of the imaginary axis. 
     The location where the imaginary axis is defined in part by the first conduit may be where the first conduit portion reaches the barrier. For example, in  FIG.  17   , the first conduit portion may include a collar  1734  attached to the baseplate. An internal perimeter of the collar at a location  1736  where the collar reaches the exterior opening in the barrier may be the location where the center of the first conduit portion is used to help define the imaginary axis. In some embodiments, the device may not protrude into the barrier, and an opening in the baseplate which abuts the barrier may be considered to be a first conduit portion, and the internal perimeter at the location where the baseplate opening abuts the barrier may be considered to be the portion which is used in part to define the imaginary axis. The center of the first conduit portion is the center of a circle in many embodiments. If the inside perimeter of the first conduit is not a circle, for purposes herein, the center of the conduit is considered to be the centroid. 
     In some embodiments where the second conduit portion is pivotable about a pivot axis, the imaginary axis may be aligned with the pivot axis. In some embodiments, the imaginary axis may be parallel to the pivot axis. The imaginary axis may be constructed in other embodiments disclosed herein, including at least  FIGS.  18 - 23   . 
     In some embodiments, an imaginary vertical plane may be defined in a plane which includes the imaginary vertical axis. For example, an imaginary vertical plane  1782  is shown in  FIG.  18   , and imaginary vertical plane  1782  may include the imaginary vertical axis as described above. The imaginary vertical plane may be perpendicular to the baseplate in some embodiments. 
       FIG.  19    shows one embodiment of a device  1900  that is similar to the embodiment shown in  FIGS.  1  and  3   , but in  FIG.  1    the device is mounted to a barrier having a single skin.  FIG.  19    shows the barrier partially penetrated by the first conduit portion  1908 . In some embodiments, no portion of the device penetrates the barrier and the first conduit portion  1908  is aligned with the opening in the barrier. Device  1900  includes a first conduit portion  1908  which is configured to pass through at least a portion of a barrier  1904 . Notably, the barrier  1904  may be a single solid piece of material, such as a glass pane. That is, the first conduit portion  1908  may provide fluid communication between two spaces separated by the barrier  1904 , where the barrier does not include any air gap or internal space. As shown in  FIG.  19   , a second conduit portion  1910  is attached to a second conduit support  1912 , which in this embodiment is a cylinder with an internal diameter that accepts the external diameter of the second conduit portion. The first conduit and second conduit support,  1908 ,  1912  are shown as being integrally formed with a baseplate  1914 , though in other embodiments, one or both of the conduit supports may be separately formed and then attached to the base baseplate  1914 . 
     According to the embodiment of  FIG.  19   , the second conduit portion  1910  has a longitudinal axis  1916  which is angled relative to a longitudinal axis  1918  of the first conduit  1908 . With the first conduit portion longitudinal axis  1918  being horizontal in the illustrated embodiment, the longitudinal axis  1916  of the second portion is inclined relative to a horizontal plane. Accordingly, in the orientation shown in  FIG.  19   , to move a ball  1920  (or other movable element) upwardly within the second conduit portion, the space on the right hand side of the barrier  1904  will need to have a pressure that is higher than the pressure on the left hand side of the barrier. Additionally, to move the ball, the pressure difference between the two spaces will have to provide enough force on the ball to overcome the gravitational force on the ball. In this manner, the weight of the ball and the incline of the second conduit portion establish a threshold pressure differential. 
     According to the embodiment of  FIG.  19    and similar to the embodiment of  FIGS.  1 - 4   , the device  1900  includes two mounting holes  1930 ,  1932  on the baseplate  1914  to aid in mounting the device to a wall or other barrier. In the illustrated embodiment, the mounting holes are positioned 180° apart from each other and positioned relative to the second conduit such that the second conduit is pitched at the maximum angle relative a horizontal plane when the mounting holes are aligned vertically. Such an arrangement can ease installation by not requiring measurements or calibrations to be performed beyond confirming a suitable roll orientation and confirming that the device is plumb. 
     The illustrated embodiment may be installed in either of two orientations when the mounting holes are vertically aligned. In this manner, the device may be used to indicate positive pressure when mounted in a first orientation, or to indicate negative pressure when mounted in a second orientation. Other orientations are possible if the mounting holes are rotated to be not vertically aligned. However, installation procedures can be set forth in a straightforward manner to achieve a desired set point by manufacturing a device with second conduit portion which does not change in angle relative to the first conduit portion, and instructing the installer to align the mounting holes vertically. 
     In some embodiments, to maintain a constant angle between longitudinal axis  1916  of second conduit portion  1910  and longitudinal axis  1918  of first conduit portion  1908 , the first conduit portion and second conduit portion are connected such that the supports are fixed relative to each other from an orientation standpoint. Conduit support  1912  cannot be rotated relative to the first conduit portion  1908  in the illustrated embodiment. In this manner, once conduit support  1912  is fixed to the wall via baseplate  1914 , the angle of inclination is set and not adjustable without removing the baseplate. 
     In the illustrated embodiment, longitudinal axis  1918  is horizontal, though in some embodiments, longitudinal axis  1918  may be non-horizontal. Having longitudinal axis  1918  be horizontal helps permit baseplate to be oriented in either of two orientations that are 180° opposite to each other in a manner which allows second conduit portion  1910  to have either of two opposite angles (e.g., +5° or −5°, or +15° and −15°). 
     According to some embodiments as shown in  FIG.  19   , the device includes a first level  1934  and a second level  1936  which are disposed on the baseplate  1914  and are used to assist in mounting the rotatable base to a first side of the barrier to confirm that the second conduit portion is inclined at the correct angle. The second level  1936  is arranged in a direction transverse to the first side of the barrier and is configured to indicate whether the baseplate  1914  is aligned with a vertical plane. When the baseplate is secured to the barrier, the second level also may indicate whether the barrier is out of plumb and not vertical. If the baseplate is not aligned with a vertical plane in the illustrated embodiment, the angle of inclination of the second conduit portion will not have the correct angle of inclination which establishes the threshold pressure differential set point. An installer may set the correct threshold pressure set point by ensuring the second level  1936  indicates alignment of a rear of the baseplate with a vertical plane. For example, if the wall is not plumb, the baseplate  1914  may be shimmed or otherwise adjusted until the second level  1936  shows that the device is correctly aligned. In one embodiment, the second level  1936  may use an air bubble in liquid to indicate whether the device is oriented correctly, though other arrangements may be used. 
     According to the embodiment of  FIG.  19   , the first level  1934  is configured to allow an installer to see whether a roll orientation of the baseplate  1914  on the barrier is correct, and therefore the first level is oriented perpendicularly to the second level  1936 . That is, the first level indicates when the baseplate is in a correct roll orientation relative to the barrier so that the roll orientation of the second conduit portion is correct. 
     According to the embodiment of  FIG.  19   , the device  1900  may include a fire stop system that, upon the detection of a threshold level of smoke or fire, provides a barrier that blocks or otherwise mitigates travel of the smoke/fire from one space or room to another. The fire stop system may include various components used to seal the passage within the wall. For example, as shown in  FIG.  19   , the fire stop system may include a single fire stop ring  1950  located on the barrier  1904 . The fire stop ring may include an intumescent substance that swells significantly as a result of heat exposure. The fire stop materials may be appropriately installed, for example, employing intumescent material as known to those of ordinary skill in the art. In some cases, the intumescent substance may produce char, which is a substance that acts to retard heat transfer. Devices of exemplary embodiments herein may be employed in fire-rated or non-fire-rated applications, as the present disclosure is not so limited. 
     According to the embodiment of  FIG.  19   , the second conduit support  1912  may be constructed with an opaque material so that the ball is not visible from the side of the device. In this manner, the presence or absence of the ball can be readily noticed to understand whether the threshold pressure differential is being met. By hiding or at least partially hiding the ball in the second conduit portion support (e.g. a collar), it is not necessary for the ball to pass through the barrier  1904  for the ball to be hidden. Accordingly, the first conduit portion  1908  may have a smaller diameter than the ball, which may reduce the size of the penetration that is made through the wall to install the device. For example, the ball may have a diameter of 1.5 inches, and the second conduit portion may have an inside diameter slightly larger than the ball. The first conduit portion  1908  may have an inner diameter of one inch, or half an inch, or any other suitable inner diameter that is smaller than the diameter of the ball. 
     In some embodiments, a device may not extend into a barrier or wall to which it is attached. For example, in some embodiments the device may be positioned only on a single side of the barrier. According to some embodiments, a device may only include a single inclined conduit, where the inclined conduit does not penetrate the barrier. That is, the device may be attached to a single side of the wall (e.g., with fasteners such as mechanical fasteners or adhesives) without any portion of the device protruding through the barrier. Of course, in other embodiments a device may fully or partially penetrate a barrier, as the present disclosure is not so limited. 
       FIG.  20    shows an embodiment of a threshold directional differential pressure indicator device  2000  configured to provide a reduced radial extent of a second conduit portion  2010  from a rotation axis of the second conduit portion, similar to the embodiment of  FIG.  15   . In the orientation illustrated in  FIG.  20   , an airflow path  2009  between a first conduit portion  2002  and the second conduit portion  2010  travels in a first lateral direction upon exiting the first conduit, and then turns and travels in a second lateral direction within the second conduit portion. This arrangement allows the second conduit portion to be positioned farther to the left (from the viewpoint of  FIG.  20   ) as compared to an arrangement where the airflow path exits the first conduit portion and makes a single turn into the second conduit portion. According to the embodiment of  FIG.  20   , the device  2000  is mounted on a single side of a barrier  2004 . The barrier  2004  may be formed as solid object, having no interior volume or space. For example, the barrier  2004  may be configured as a glass pane. A baseplate  2014  of the device may be secured to the barrier  2004  with a suitable fastener such as a mechanical fastener or adhesive. While in the embodiment of  FIG.  20    the device may protrude into the barrier  2004  slightly, in other embodiments the device may be mounted solely on one side of barrier, where no portion of the device protrudes into the barrier. Of course, in other embodiments the device may protrude partially through a barrier, as the present disclosure is not so limited. 
     According to the embodiment of  FIG.  20   , a movable element such as a ball  2020  has a travel path, such as a travel path  2015 . When the travel path starts at a lateral position which is at or near the lateral position of a rotation axis of the second conduit portion  2010 , the second conduit extends radially by approximately the length of the second conduit portion (when the second conduit portion is parallel to the wall). By shifting the second conduit portion, the travel path  2015  of the ball  2020  crosses the location of the rotation axis, and reduces the lateral extent of the second conduit portion from the rotation axis, which may be the approximate center of the device in the front view. Put alternatively, the second conduit portion  2010  has a longitudinal travel path for a movable element that extends transversely to a longitudinal axis of the first conduit portion. The travel path extends beyond the longitudinal axis of the first conduit portion in two opposite directions. In this manner, the travel path in the second conduit portion may be intersected (in some cases bisected) by the longitudinal axis of the first conduit portion. In some embodiments, the travel path of the second conduit portion may be perpendicular to the longitudinal axis of the first conduit portion. The travel path for the movable element need not be linear to have a longitudinal direction. If the travel path is curved, then the longitudinal direction of the travel path also has a curve. For purposes herein, an axis or direction which is said to be transverse to a different axis or direction need not necessarily intersect with the different axis or direction. The axes or directions may be in different planes and not parallel, and be considered to be transverse. Embodiments herein with axes and/or directions which are indicated to be transverse may also intersect in some embodiments. 
       FIG.  21    shows an embodiment of a threshold directional differential pressure indicator device  2000  configured to provide a reduced radial extent of a second conduit portion  2010  from a rotation axis of the second conduit portion, similar to the embodiment of  FIG.  20   . Like  FIG.  20   , and in the orientation illustrated in  FIG.  21   , an airflow path  2009  between a first conduit portion  2002  and the second conduit portion  2010  travels in a first lateral direction upon exiting the first conduit, and then turns and travels in a second lateral direction, substantially opposite to the first lateral direction within the second conduit portion. According to the embodiment of  FIG.  21   , the device  2000  is mounted on a single side of a barrier  2004 , where no portion of the device protrudes into an opening  2022  formed in the barrier  2004 . The barrier  2004  may be formed as solid object, having no interior volume or space. For example, the barrier  2004  may be configured as a glass pane. A baseplate  2014  of the device may be secured to the barrier  2004  with a suitable fastener such as a mechanical fastener or adhesive. As shown in  FIG.  21   , the device also includes a seal  2024  positioned between the baseplate  2014  and the barrier  2004 . The seal may be configured as an O-ring or another suitable seal that prevents air from passing between the baseplate  2014  and the barrier  2004 . In some embodiments, the fastener attached the baseplate to the barrier (such as adhesive) may form the seal between the baseplate and the barrier. 
       FIG.  22    shows an embodiment of a threshold directional differential pressure indicator device  2200  where movable element  2220  is positionable entirely to a first side of pivot axis  2215  when the movable element is contacting a movable element stop  2230 —the movable element is shown in dashed lines in this position. In some embodiments, a portion of the movable element extends to a first side of pivot axis  2215 . When the movable element  2220  is contacting a distal movable element stop  2240 , the movable element is shown as entirely on a second side, opposite from the first side, of the pivot axis  2215 . In some embodiments the line representing pivot axis  2215  may instead or additionally represent an imaginary axis or an imaginary plane (such as a vertical plane) as explained above with reference to  FIGS.  17 - 18   . When discussing proximal and distal movable element stops, the terms proximal and distal are used in a relative sense. A proximal movable element does not necessarily mean that the proximal movable element is at an end of a conduit portion, and likewise, a distal movable element does not necessarily mean that the distal movable element is at an end of a conduit portion. Generally, the term proximal is used herein for a component which is configured to be closer to the barrier opening along a fluid connection path or air flow path when the device is mounted, as compared to a more distal component which is configured to be farther from the barrier opening along a fluid connection path or air flow path when the device is mounted. 
     A photoelectric sensor  2250  may be positioned at one or both regions of a travel path section  2260  to either side of the pivot axis. 
     A plenum  2252  may be present adjacent to a proximal end of the travel path section  2260 . The plenum may serve to help align air flow so that as air flow can enter an opening  2242  located on an end face of travel path section  2260 . By entering through an end face, the air flow is more aligned with a longitudinal direction of the travel path section that if the air flow were to enter from a sidewall of the travel path section. 
     The second conduit portion may be attached to a rotating base  2380  which is rotatable relative to baseplate  2214 . 
     A flow path  2270  shows how fluid may travel from an opening in baseplate  2278 , through first conduit portion  2202 , and to opening  2242  through several bends. The path is shown as turning ninety degrees three times. Fluid may flow in either direction in some embodiments. In some embodiments, and as shown in  FIG.  22   , the path may reverse on itself by one hundred eighty degrees. In some embodiments, the path may change direction in the plenum  2252  by at least one hundred thirty-five degrees. 
     The cross-hatched portion of the movable element travel path section  2260  may be transparent in some embodiments, while the non-cross-hatched portion may be opaque in some embodiments, such that the movable element  2220  is visible when located at the distal ball stop  2240 , and not as readily visible when located at proximal ball stop  2230 . 
       FIG.  23    illustrates a similar embodiment a shown in  FIG.  22   , but with a second conduit portion  2358  and a travel path section  2360  being transverse to a base plate  2314 . This embodiment is shown as being non-rotatable, though the structure may be mounted in a rotating manner to a baseplate to allow rotation. An imaginary axis is shown as perpendicular to the baseplate and/or barrier  2304  and passes through a center of the first conduit portion  2302  where the first conduit portion is configured to reach the barrier  2304 . This imaginary axis intersects the second conduit portion  2358 , and movable element  2320  may at least partially cross the axis, and may fully cross the axis as shown in  FIG.  23   . The movable element  2320  may be positioned entirely to one side of the imaginary axis  2315  when contacting a proximal ball stop  2330 , and may be positioned entirely to the opposite side of the imaginary axis when contacting a distal ball stop  2340 . 
     The cross-hatched portion of the movable element travel path section  2360  may be transparent in some embodiments, while the non-cross-hatched portion may be opaque in some embodiments, such that the movable element  2320  is visible when located at the distal ball stop  2340 , and not as readily visible when located at proximal ball stop  2330 . 
     Various embodiments disclosed herein may include a threshold directional differential pressure set point indicator mounted to the baseplate—the threshold directional pressure difference being the difference which is sufficient to cause the movable element to move from a lower region of the inclined conduit to a higher region. The directional differential pressure set point indicator may include, for example, a bubble vial, a rotating weighted pendulum pointer, or any other suitable component that responds to the incline of the conduit. In the descriptions presented above, the pitch and the roll indicators, used together, provide a calibration to allow the device to be installed to a desired pitch and roll orientations of the inclined conduit containing the moveable element, such that the desired orientation corresponds to the desired directional differential pressure set point between the two separate spaces. 
     The pressure difference required to move the ball from a home position (the ball&#39;s position when there is no pressure difference between the rooms) can vary based at least on the physical features of the conduit (e.g., passageway diameter, straightness/curvature, surface finish), physical features of the ball (e.g., diameter, weight, surface finish), degree of incline of the conduit, fluid properties of the media between compartments, and the orifice sizes at the end stops. In many cases, each of the above parameters is known to a sufficient degree such that threshold directional pressure differences can be linked to the angle of inclination of the conduit portion within which the movable element travels. In some embodiments, balls of different weights may be used to adjust the threshold pressure differences. In such embodiments, the conduit angle may or may not be adjustable. 
     As an example, for a hospital isolation room occupied by a patient with an infectious disease that is capable of airborne transmission, it may be desirable to keep the room at a negative differential pressure relative to one or more adjacent rooms, so as to substantially prevent airborne transmission of the disease to an adjacent room. In such an arrangement, the room&#39;s ventilation system exhausts more air than is supplied within it to an extent that the negative pressure is of a greater magnitude than any adjacent space. Thus, the device may be installed in the corridor, outside of the isolation room. The inclined conduit is installed with a downward orientation such that the end of the conduit that is closer to the wall toward the isolation room is at a higher position than the opposite end of the conduit that is away from the wall in the corridor. 
     When the net directional differential pressure between the isolation room and the outside space is zero (e.g., a door between the room and the outside space is opened), or the pressure in the isolation room is greater than the adjacent spaces, the ball will fall to the lower end of the conduit such that an observer in the corridor would see the ball at the bottom of the lower end, farthest away from the wall. When the appropriate degree of negative pressure is applied to the room to overcome gravity and the device characteristics, the ball moves upwardly within the conduit toward the wall to the vertically higher end of the inclined conduit. That is, the difference between the pressure of the isolation room and the pressure in the corridor outside on the opposite side of the wall causes forces on the ball that are sufficient to move the ball upwardly, thereby indicating that at least the appropriate direction of air flow through an opening between the rooms and degree of negative pressure is applied to the isolation room to prevent the escape of infectious pathogen air in the isolation room. It should be noted that Applicant has appreciated that the communicating conduit can not only be through one wall or barrier and sense the pressure conditions on each side, but, in some embodiments, the conduit may leave a room and pass through adjacent spaces and open up to a space not immediately adjacent to the initial room. 
     In the case of a hospital operating room that is required to exhibit a positive pressure, so as to substantially prevent potentially contaminated air from flowing into the room from a surrounding space, the device may be installed in the corridor outside of the operating room such that the end of the conduit that extends toward the operating room is at a lower position than the opposite end of the conduit that extends away from the operating room and into the corridor. Thus, when a suitable amount of positive pressure is applied to the operating room, there is sufficient directional differential pressure to move the ball upwardly, farthest away from the wall to the higher end of the conduit. 
     The inclined conduit containing the ball may be clear to allow visibility of the position of the ball. The conduit may be of a length that is twice as long as the diameter of the ball in some embodiments. The conduit may have an opaque cover at the half-end of the conduit closest to the wall the device is mounted to on one side of the wall. When the ball travels to a position closest to the wall, the ball may be hidden when the device is viewed from the side. This feature facilitates a view of the position of the ball. 
     When installed, the conduit may be oriented at an appropriate angle of inclination that corresponds to the desired threshold differential pressure set point. In some embodiments, the desired differential pressure set point may be between 0.001 inch of H 2 O and 10 inches of H 2 O (e.g., between 0.001 inch of H 2 O and 1 inch of H 2 O, between 0.001 inch of H 2 O and 5 inch of H 2 O, between 0.005 inches of H 2 O and 0.5 inches of H 2 O, between 0.1 inch of H 2 O and 0.5 inches of H 2 O, between 0.01 inch of H 2 O and 0.1 inches of H 2 O, between 0.01 inch of H 2 O and 0.05 inches of H 2 O, between 0.01 inch of H 2 O and 0.03 inches of H 2 O, between 0.005 inches of H 2 O and 0.1 inch of H 2 O, between 0.001 inch of H 2 O and 0.005 inches of H 2 O, between 0.001 inch of H 2 O and 0.003 inches of H 2 O, etc.), as measured by a standard water column manometer. It will be appreciated that devices of the present disclosure may provide an indication of other differential pressures between adjacent spaces outside of these ranges. 
     Physical features other than the incline of the conduit may provide an indication of whether the directional differential pressure between spaces meets a certain threshold. For instance, the type of ball placed within the conduit may be chosen based on particular characteristics, such as weight or surface finish of the ball. For example, a greater differential pressure will be required to move a heavier ball from a lower region of the conduit to a higher region of the conduit. Conversely, if the ball is lighter, a smaller differential pressure will be required to move the ball toward the higher end of the conduit. Alternatively, a ball having a rough surface finish may require a greater degree of air flow provided through differential pressure to move the ball toward the higher end of the conduit. Accordingly, different balls, or movable elements, may be marked according to the range of differential pressure that the detector, incorporating the particular ball(s), may indicate. For example, two or more movable elements having different weights may be provided, each with a different color and/or markings. The markings may indicate what threshold differential pressure set point is set when the particular movable element (e.g., ball) is used in the conduit. When the device is configured to permit only one inclination, the movable element may have a pressure marking directly on the movable element. A user may select which movable element (e.g., ball) to place in the device from among a plurality of movable elements of different weights. Or the user may select which movable element (e.g., ball) to place in the device from among a plurality of movable elements having different diameters. In this manner, a second ball may be swapped for a first ball by removing the first ball from the conduit and inserting the second ball into the conduit. Other parameters may include the diameter of a ball and the inside diameter of the inclined conduit containing the ball. 
     In some embodiments, an end stop that forms a suitable fit (e.g., interference fit, snap fit) over an end of a conduit may include a sound attenuator. In some cases, a movable element may be a plastic ball (e.g., a ping pong ball) and the end stop may be made of a hard plastic. Thus, without inclusion of the sound attenuator between the conduit and the end stop, when the ball impacts against the end stop, an abrupt sound may be produced which can be easily heard by a person located in the space where the impact occurs, and possibly in an adjacent space where the other open end of the conduit resides. When the sound attenuator is placed between the conduit and the end stop, impact of the ball against the sound attenuator will produce a much softer sound which is not as readily noticeable as compared with the sound produced when the energy-absorbing material is not present. The sound attenuator may be formed in a separate layer on the end stop, or may be integrated into the end stop (e.g., the end stop may exhibit a geometry similar to a diaphragm), as the present disclosure is not so limited. 
     In some embodiments, there may not be an alignment of the travel path of the center of the ball and an opening at the end of the conduit. For example, an interior-facing portion of an opening at the end of the conduit may be arranged and positioned such that the movable element substantially prevents air flow when the movable element abuts the interior-facing portion of the opening, yet a center axis of the opening (e.g., the centroid of the area of the opening) is not aligned with a travel path of a center of the movable element. A ramp may be present toward the end of the conduit such that the movable element is pushed up into the opening. 
     Screws may be used to mount a baseplate to a wall, though other suitable fasteners may be used. It should be noted that while screws are shown in exemplary embodiments described herein, any suitable arrangement may be employed to join various components. 
     The conduit(s) of exemplary embodiments described herein may include any suitable material. In some embodiments, the conduit(s) may be made up of glass, plastic, or another appropriate material. In some cases, the conduit(s) may be transparent or translucent so that the movable element within the conduit is viewable to an observer. In some embodiments, the conduit(s) are rigid, though, in various embodiments, the conduit(s) are flexible. The device may include a combination of rigid and flexible conduits. For example, a flexible conduit may be used within a barrier as part of a connection between a first space on one side of the barrier and a second space on the other side of the barrier. The flexible conduit may connect to a collar on the back side of baseplate in some embodiments. A conduit need not be cylindrical in shape as any suitable shape may be used. 
     For purposes herein, a first component being connected or attached to a second component does not necessarily require that the first and second component be directly connected to one another. The first component may be connected to the second component via a third component. For example, a second conduit portion may be attached to a baseplate via a first conduit portion. Or a conduit portion may be attached to a baseplate via a rotating base. 
     While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.