Patent Publication Number: US-2022215737-A1

Title: Gas Monitoring And Alarm Systems And Methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/862,318, filed on Apr. 29, 2020, which is a continuation of U.S. patent application Ser. No. 16/112,536, filed on Aug. 24, 2018 (now U.S. Pat. No. 10,679,483), which claims benefit of U.S. Provisional Patent Application Ser. No. 62/550,497, filed on Aug. 25, 2017, and U.S. Provisional Patent Application Ser. No. 62/633,451, filed on Feb. 21, 2018, the entire contents of which are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention generally concerns systems and methods for gas monitors and alarms. More specifically, the invention discloses systems and methods for monitoring gas levels and triggering alarms when high gas levels are detected. 
     BACKGROUND OF THE INVENTION 
     Many residential homes and business facilities utilize appliances and other systems that contain or emit gas that is harmful to humans at or above certain concentrations. For instance, many businesses that offer food and drink utilize soda-dispensing machines that use carbon dioxide to carbonate beverages. Carbon dioxide is lethal to humans above a certain concentration, but it is typically kept in cylinders that are intended to keep the gas contained and within safe concentrations for humans working in close contact with the gas. In the event of a leak, however, the concentration of the gas can rise rapidly to unsafe levels, especially in small, confined areas. Carbon dioxide, like many gases, is odorless and colorless, and thus cannot be detected by humans even in hazardously high concentrations without the aid of a gas monitoring system. 
     Existing gas monitoring and/or alarm systems merely sense the presence of a gas and may alert those nearby to its presence. Some systems may also alert emergency responders, such as the fire department. However, these systems are not designed to also trigger evacuation of the gas to quickly bring the concentration of the gas in the area back down to a safe level. Moreover, many of these systems are not designed with mechanisms for providing power backup to these lifesaving systems that may otherwise cease operating in the event of a power failure. 
     Additionally, existing gas monitors typically have an integrated sensor such that the sensor unit and the monitor itself must be physically located in the same area. This is problematic if a user must be near the monitor to know whether gas levels in an area are unsafe; by the time the user is close enough to see the monitor, the user may have already entered a potentially hazardous area. Additionally, most current systems utilize a standalone monitor requiring its own power source. If multiple areas within a building (e.g., different rooms in a building) are being monitored, an entirely separate sensor must be installed in each area. 
     Gas monitoring and alarm systems designed to overcome one or more of the aforementioned challenges are desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a block diagram of a gas monitoring and alarm system; 
         FIG. 2  is a block diagram of a primary monitor, a remote display unit, and a relay interface of the gas monitoring and alarm system of  FIG. 1 ; 
         FIG. 3  is a block diagram of a relay interface of a gas monitoring and alarm system according to a first embodiment; 
         FIG. 4A  is a front view of an exemplary gas monitoring and alarm system according to the first embodiment; 
         FIG. 4B  is a front view of a relay interface of the gas monitoring and alarm system of  FIG. 4A ; 
         FIG. 5  is a block diagram of a relay interface of the gas monitoring and alarm system according to a second embodiment; 
         FIG. 6A  is a front view of an exemplary gas monitoring and alarm system according to the second embodiment; 
         FIG. 6B  is a front view of a relay interface of the gas monitoring and alarm system of  FIG. 6A ; 
         FIG. 7  is a block diagram of a relay interface of the gas monitoring and alarm system according to a third embodiment; 
         FIG. 8A  is a front view of an exemplary gas monitoring and alarm system according to the third embodiment; 
         FIG. 8B  is a front view of a relay interface of the gas monitoring and alarm system of  FIG. 8A ; 
         FIG. 9  is a block diagram of a relay interface of the gas monitoring and alarm system according to a fourth embodiment; 
         FIG. 10A  is a front view of an exemplary gas monitoring and alarm system according to the fourth embodiment; 
         FIG. 10B  is a front view of a relay interface of the gas monitoring and alarm system of  FIG. 10A ; 
         FIG. 11  is a block diagram of a relay interface of the gas monitoring and alarm system according to a fifth embodiment; 
         FIG. 12A  is a front view of an exemplary gas monitoring and alarm system according to the fifth embodiment; 
         FIG. 12B  is a front view of a relay interface of the gas monitoring and alarm system of  FIG. 12A ; 
         FIG. 13A  is a block diagram of a gas monitoring system with a master monitor; 
         FIG. 13B  is a front view of an exemplary gas monitoring system with a master monitor; 
         FIG. 14A  is a block diagram of a master monitor of the gas monitoring system of  FIGS. 13A-13B ; 
         FIG. 14B  is a front view of an exemplary master monitor and master monitor sensor; 
         FIG. 14C  is a front view of the master monitor of  FIG. 14B ; 
         FIG. 14D  is a front view of the master monitor sensor of  FIG. 14B  with a faceplate secured; 
         FIG. 14E  is a front view of the master monitor sensor of  FIG. 14D  with the faceplate removed; 
         FIG. 15A  is a block diagram of a master monitor and a slave monitor of the gas monitoring system of  FIGS. 13A-13B ; 
         FIG. 15B  is a front view of an exemplary slave monitor and slave monitor sensor; 
         FIG. 15C  is front view of the slave monitor of  FIG. 15B ; 
         FIG. 15D  is a front view of the slave monitor sensor of  FIG. 15B  with a faceplate secured; 
         FIG. 15E  is a front view of the slave monitor sensor of  FIG. 15D  with the faceplate removed; 
         FIG. 16  is a front view of an exemplary gas monitoring system; 
         FIG. 17  is a flow diagram illustrating a first method for monitoring gas levels and triggering an alarm system; and 
         FIG. 18  is a flow diagram illustrating a second method for monitoring gas levels and triggering an alarm system. 
     
    
    
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a system is disclosed. The system includes a master monitor and at least one remote monitor. The master monitor is coupled to a master sensor that senses a concentration of a gas in a first area and sends data to the master monitor. The at least one remote monitor is communicatively coupled to the master monitor. The least one remote monitor is coupled to a remote sensor, which senses a concentration of gas in a second area. The at least one remote monitor receives data about the concentration of the gas in the second area from the remote sensor, and sends the data to the master monitor. The master monitor receives the data and triggers a first alarm status when the concentration of gas in at least one of the first area and the second area exceeds a first predefined alarm threshold. 
     In yet another aspect of the present invention, a system is disclosed. The system includes a master monitor and at least one remote monitor. The master monitor is coupled to a master sensor, which is configured to sense a concentration of a gas in a first area and send data about the concentration of the gas to the master monitor. The at least one remote monitor is communicatively coupled to the master monitor. The at least one remote monitor is configured to receive data about the concentration of the gas from the master monitor. The master monitor is further configured to trigger a first alarm status when the concentration of gas in the first area exceeds a first predefined alarm threshold, send data about the alarm status to the remote monitor, and activate an alarm system when the alarm status is triggered. 
     In another aspect of the present invention, a method is disclosed. A master monitor coupled to a master sensor is provided. The master sensor configured to sense a concentration of a gas in a first area and send data about the concentration of the gas to the master monitor. At least one remote monitor communicatively coupled to the master monitor is provided. The at least one remote monitor is coupled to a remote sensor configured to sense a concentration of gas in a second area. The at least one remote monitor receives data about the concentration of the gas in the second area from the remote sensor. The at least one remote monitor sends the data to the master monitor. The master monitor receives the data from the at least one remote monitor. The master monitor triggers a first alarm status when the concentration of gas in at least one of the first area and the second area exceeds a first predefined alarm threshold. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention provide systems and methods for monitoring and detection of gas levels, and triggering alarms when high levels of gas(es) are detected. Persons of ordinary skill in the art will realize that the following description of the presently invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons. According to the present invention, a system may include any combination of a gas monitoring and/or detection system and/or an alarm system. 
     Gas Monitoring and Alarm System with Optional Relay Interface 
     Referring to  FIG. 1 , a block diagram of a gas monitoring and alarm system is shown. A gas monitoring and alarm system  100  comprises a primary monitor  102 , a remote display unit  104 , and an optional relay interface  106 . Primary monitor  102  and relay interface  106  may be located at a source location  103 . Remote display unit  104  may be located at a remote location  105 . In some embodiments, there may be more than one remote location  105  if there are more than one remote display units  104  being utilized by system  100 . In some embodiments, the relay interface  106  may be an optional component of system  100 . 
     Referring now to  FIG. 2 , a block diagram of a primary monitor, a remote display unit, and an optional relay interface of the gas monitoring and alarm system of  FIG. 1  is shown. Primary monitor  102  comprises a gas sensor  108 , a primary monitor horn  110 , a primary monitor display screen  112 , and a control logic  113 . Control logic  113  may be a computer, including a microprocessor, a programmable logic controller, or any other type of suitable controller for receiving sensor information and performing the operations described herein, including controlling horn/strobes, display screen of the primary monitor  102  and indicators thereof, the display of remote display unit  104  and indicators thereof, and relay interface  106 , as described in more detail below. Primary monitor  102  further comprises a first alarm level indicator  114 , a second alarm level indicator  116 , a fault indicator  118 , reset button  122 , and internal relays  127 ,  129 . In some embodiments, primary monitor  102  and/or remote display unit  104  may be configured to connect to, and send and receive data over, a wireless network, such as a WiFi network, cellular, or other network which enables primary monitor  102  and/or remote display unit  104  to send, for example, status reports and other data to remote locations and devices outside of system  100 . 
     The first alarm level may be adjustable to a first predefined concentration threshold. For instance, in the embodiment shown, a factory default setting is a concentration of CO 2  at 1.5% or 15,000 parts per million (PPM). The second alarm level may also be adjustable to a second predefined concentration threshold. For instance, in the embodiment shown, a factory default setting is a concentration of CO 2  at 3% or 30,000 parts per million (PPM). Thus, the two-level alarm system may allow detection of a gas at varying concentrations, with varying responses to gas detection at each level. Primary monitor display screen  112  may display information about the detected concentration levels of a gas. 
     Primary monitor  102  is activated when a gas is detected by the gas sensor  108 . In the embodiments shown herein, gas sensor  108  detects carbon dioxide (CO 2 ), but it will be understood that the present invention may be used to detect any gas at any concentration. When gas sensor  108  senses a gas at a concentration at or above the first predefined concentration threshold, the first alarm level indicator  114  and primary monitor horn  110  may be activated. First alarm level indicator  114  may comprise, for example, a blinking light, such as a red LED light. Primary monitor horn  110  may emit intermittent sounds at a predefined decibel level. Moreover, primary monitor  102  is connected to primary monitor strobe  120 , which may be external to primary monitor  102 . Primary monitor strobe  120  may begin to flash when the first alarm level is activated. 
     If gas sensor  108  detects that the concentration of the gas drops below the first predefined concentration threshold, first alarm level indicator  114  may discontinue blinking, primary monitor horn  110  may discontinue sounding, and primary monitor strobe  120  may discontinue flashing. 
     If gas sensor  108  detects that the concentration of the gas continues to rise above the second predefined concentration threshold, first alarm level indicator  114  will continue to blink. Primary monitor horn  110  may continue sounding and primary monitor strobe  120  may continue flashing, both at an increased tempo. Additionally, second alarm level indicator  116  may be activated. Second alarm level indicator  116  may comprise a blinking light, such as a red LED light. 
     Moreover, when the concentration of the gas meets or exceeds the second predefined concentration threshold, fault indicator  118  may be activated. Fault indicator  118  may comprise a flashing light, such as an amber LED light. Fault indicator  118  may continuously flash until primary monitor  102  is reset, either by pressing a reset button  122  or disrupting a power supply  124  connected to primary monitor  102 . 
     If gas sensor  108  detects that the concentration of the gas drops below the second predefined concentration and the first predefined concentration threshold, first alarm level indicator  114  and second alarm level indicator  116  may discontinue blinking, primary monitor horn  110  may discontinue sounding, and primary monitor strobe  120  may discontinue flashing. If gas sensor  108  detects that the concentration of the gas drops below the second predefined concentration but is still above the first predefined concentration threshold, second alarm level indicator  116  may discontinue blinking, but first alarm level indicator  114  may continue blinking and primary monitor horn  110  may continue sounding, and primary monitor strobe  120  may continue flashing, until gas sensor  108  detects that the concentration of the gas has dropped below the first predefined concentration threshold. 
     Primary monitor  102  is further coupled to remote display unit  108  (e.g., by a CAT6 cable, a CAT5 cable, or other Ethernet/network cable suitable to allow the primary monitor  102  to communicate with the remote display unit  108 ), which is intended to be placed externally to the primary monitor  102  and ideally in area separate from the gas-containing device that is being monitored (e.g., a CO 2  tank). Remote display unit  104  acts as an entry pre-warning device, such that it can be conveniently observed by a person before they enter the room where the primary monitor  102  and the gas-containing device are located. Remote display unit  104  may be a satellite information repeater, and displays the measurements made by primary monitor  102  on a remote display unit screen  126 , such as a digital LCD screen. In some embodiments, there may be more than one remote display unit  104 , which may be in more than one remote location. Remote display unit  104  further comprises a remote display unit horn  128 , and is coupled to a remote display unit strobe  130 . When the first alarm level and the second alarm level of primary monitor  104  are activated, remote display unit horn  128  and remote display unit horn strobe  130  are activated. When gas concentrations drop below the first predefined concentration threshold, remote display unit horn  128  and remote display unit horn strobe  130  will disengage. In some embodiments, remote display unit  104  may instead be controlled by a distinct controller separate from the control logic  113 , such that the remote display unit controller controls the operations related to the remote display unit  104  (e.g., operation of the remote display unit horn  128 , remote display unit screen  126 , etc.). In some embodiments, the controllers of the primary monitor  102  and the remote display unit  104  may be in communication over a network, such as a wireless, cellular, Ethernet, or LAN network, or any other suitable network to facilitate communication between the controllers. 
     In some embodiments, primary monitor  102  and/or remote display unit  104  may be capable of communicating over a wireless network such as a WiFi network, cellular, or other network which enables primary monitor  102  and/or remote display unit  104  to send and receive, for example, status reports and other data to and from remote locations and devices outside of system  100 . 
     Activation of the first alarm level of primary monitor  102  may, in some embodiments, trigger an internal relay system that activates a relay interface  106 . Relay interface  106  is discussed in more detail with respect to the various embodiments disclosed below. 
     Relay Interface First Embodiment 
     Referring now to  FIG. 3 , a block diagram of a relay interface of a gas monitoring and alarm system according to a first embodiment is shown. Relay interface  106  comprises a terminal bar  132 , a first contactor  134 , and a second contactor  136 . Terminal bar  132  generates a power supply, fed from power supply  124 , to deliver to first contactor  134 . First contactor  134  may be a 120-volt multi-purpose contactor, rated at 40 amps at 240 volts. First contactor  134  creates a circuit that is normally open and is energized by one of the primary monitor  102  internal relays  127 ,  129  upon its activation during alarm status. When first contactor  134  is energized, it closes the circuit that supplies power to an external exhaust ventilation system  138 , thereby allowing evacuation of gas when gas concentrations are at or above unsafe levels. 
     First contactor  134  is also coupled to second contactor  136 . Second contactor  136  may be a 120-volt contactor, rated at 15 amps at 240 volts. Second contactor  136  creates a circuit that is normally closed. The closed circuit is deactivated by the first contactor  134  when it is energized by one of the primary monitor  102  internal relays upon its activation during alarm status. Second contactor  136  is used to control power to a solenoid valve  140 . During normal operation, gas is allowed to flow freely though solenoid valve  140  that is powered by a 120-volt circuit that is normally closed. However, when high concentrations of gas are detected and primary monitor  102  internal relays are activated, power is supplied to first contactor  134 , thereby closing its circuit that is normally open. When this happens, power is supplied to exhaust ventilation system  138 . Furthermore, when first contactor  134  is energized, it disrupts power to the second contactor&#39;s circuit that is normally closed, there by breaking the circuit, closing solenoid valve  140 , and disrupting gas flow. 
     Referring now to  FIGS. 4A-4B , front views of an exemplary gas monitoring and alarm system and its relay interface according to the first embodiment are illustrated.  FIG. 4A  further shows external exhaust ventilation indicator  142  and solenoid valve indicator  144  that are included for illustration/demonstration purposes only. External exhaust ventilation system indicator  142  represents the exhaust ventilation system  138 , normally an open circuit. Solenoid valve indicator  144  represents the solenoid valve  140 , normally a closed circuit.  FIG. 4A  further includes optional additional exterior strobe/horn unit  146  that may be used in conjunction with the existing horns/strobes of the system as an additional safety mechanism. 
     Relay Interface Second Embodiment 
     Referring now to  FIG. 5 , a block diagram of a relay interface of the gas monitoring and alarm system according to a second embodiment is shown. Relay interface  106  comprises a terminal bar  132 , a first contactor  134 , a second contactor  136 , and a receptacle  148 . Terminal bar  132  generates a power supply, fed from power supply  124 , to deliver to first contactor  134 . Terminal bar  132  and first contactor  134  together supply power to exhaust ventilation system  138  and solenoid valve  140 . Terminal bar  132  also delivers power to receptacle  148 . Receptacle  148  may be a 120-volt receptacle that, in turn, supplies power to primary monitor  102 . 
     First contactor  134  may be a 120-volt definite-purpose contactor (3 Pole), rated at 40 amps at 240 volts. First contactor  134  creates a circuit that normally open and is energized by one of the primary monitor  102  internal relays upon its activation during alarm status. When first contactor  134  is energized, it closes the circuit that supplies power to the external exhaust ventilation system  138 , thereby allowing evacuation of gas when gas concentrations are at or above unsafe levels. 
     First contactor  134  is also interfaced with second contactor  136 . Second contactor  136  may be an auxiliary contactor, rated at 40 amps and carrying no voltage. Second contactor  136  creates a circuit that is normally closed. The closed circuit is deactivated by the first contactor  134  when it is energized by one of the primary monitor  102  internal relays upon its activation during alarm status. Second contactor  136  is used to control power to solenoid valve  140 . During normal operation, gas is allowed to flow freely though solenoid valve  140  that is powered by a 120-volt circuit that is normally closed. However, when high concentrations of gas are detected and primary monitor  102  internal relays are activated, power is supplied to first contactor  134 , thereby closing its circuit that is normally open. When this happens, power is supplied to exhaust ventilation system  138 . Furthermore, when first contactor  134  is energized, it disrupts power to the circuit of second contactor  136  that is normally closed, there by breaking the circuit, closing solenoid valve  140 , and disrupting gas flow. 
     Furthermore, according to this embodiment, relay interface  106  further comprises a receptacle  148 , which provides power to primary monitor  102  instead of power supply  124  (see  FIG. 2 ). Receptacle  148  may be a 120-volt receptacle, and is located inside relay interface  106  in order to make it more difficult for power to primary monitor  102  to be disrupted, since relay interface  106  may be encased in a closable (and, optionally, lockable) container to prevent or deter access to its components. 
     Referring now to  FIGS. 6A-6B , front views of an exemplary gas monitoring and alarm system and its relay interface according to the second embodiment are illustrated.  FIG. 6A  further shows external exhaust ventilation system indicator 142  and solenoid valve indicator  144  that are included for illustration/demonstration purposes only. External exhaust ventilation system indicator  142  represents the exhaust ventilation system  138 , normally an open circuit. Solenoid valve indicator  144  represents the solenoid valve  140 , normally a closed circuit. 
     Relay Interface Third Embodiment 
     Referring now to  FIG. 7 , a block diagram of a relay interface of the gas monitoring and alarm system according to a third embodiment is shown. Relay interface  106  comprises terminal bar  132 , first contactor  134 , second contactor  136 , a first transformer  150 , a battery charger  152 , a second transformer  154 , and a backup battery  156 . 
     Terminal bar  132  generates a power supply, fed from power supply  124 , to deliver to first contactor  134 . Terminal bar  132  and first contactor  134  together supply power to exhaust ventilation system  138  and solenoid valve  140 . Terminal bar  132  also delivers power to first transformer  150  and second transformer  154 . 
     First contactor  134  may be a 120-volt multi-purpose contactor (3 Pole), rated at 40 amps at 240 volts. First contactor  134  creates a circuit that normally open and is energized by one of the primary monitor  102  internal relays  127 ,  129  upon its activation during alarm status. When first contactor  134  is energized, it closes the circuit that supplies power to an external exhaust ventilation system  138 , thereby allowing evacuation of gas when gas concentrations are at or above unsafe levels. First contactor  134  also supplies power to first transformer  150 . First transformer  150  may be a 120-volt to 24-volt stepdown transformer. 
     First contactor  134  is also interfaced with second contactor  136 . Second contactor  136  may be an auxiliary contactor, rated at 40 amps at 240 volts. Second contactor  136  creates a circuit that is normally closed. The closed circuit is deactivated by the first contactor  134  when it is energized by one of the primary monitor  102  internal relays  127 ,  129  upon its activation during alarm status. Second contactor  136  is used to control power to solenoid valve  140 . During normal operation, gas is allowed to flow freely though solenoid valve  140  that is powered by a 120-volt circuit that is normally closed. However, when high concentrations of gas are detected and primary monitor  102  internal relays  127 ,  129  are activated, power is supplied to first contactor  134 , thereby closing its circuit that is normally open. When this happens, power is supplied to exhaust ventilation system  138 . Furthermore, when first contactor  134  is energized, it disrupts power to the circuit of second contactor  136  that is normally closed, there by breaking the circuit, closing solenoid valve  140 , and disrupting gas flow. 
     First transformer  150  supplies 24-volt power to battery charger  152 . Battery charger  152  converts the 24-volt power to  6 -volts DC, which in turn supplies power to primary monitor  102 . Battery charger  152  also monitors and trickle charges backup battery  156 . 
     When power is lost (e.g., power supply  124  is cut off) during an alarm status, battery charger  152  engages battery backup  156 , which supplies instantaneous backup power to primary monitor  102 , remote display unit  104 , primary monitor horn  110 , remote display unit horn  128 , primary monitor and remote display unit strobes  120  and  130 , and/or exterior alarm strobe/horn unit  146 . 
     Furthermore, when power is lost (e.g., power supply  124  is cut off) during an alarm status, exhaust ventilation system  138  is automatically shut down (in  FIG. 7 , a scaled version of exhaust ventilation system  138  is shown; it will be understood that the system will likely be many times larger than the one shown), despite that evacuation of the gas via this system is the primary life safety system protocol in the presence of high concentrations of dangerous gases, such as CO 2 . Therefore, battery backup  156  may be used to: (1) maintain power to primary monitor  102 , thus allowing it to continue monitoring concentration of the gas; (2) continue activation of all system horns and strobes; and (3) supply power to an optional alarm panel monitoring circuit  158 , which connects the system  100  to an external monitoring service, such as a monitoring company that can alert fire and rescue, that monitors the status of the system  100 . This power backup system allows the system to continue to alert occupants (including emergency responders) that harmful concentrations of the gas are present, even during power outages. It also allows the monitoring service to maintain a connection to the system to monitor the alarm status via the alarm panel monitoring circuit  158 . 
     Second transformer  154  may supply power to exterior strobe/horn unit  146  and an actuator  160 . Actuator  160  may be a 24-volt actuator, and may be used to open a sealed damper  162  to exhaust ventilation system  138  during an alarm status. Second transformer  154  may be a 120-volt to 24-volt stepdown transformer. Second transformer  154  may be wired through second contactor  136 . When first contactor  134  is energized, its circuit (which is normally open) is closed, thereby mechanically closing the circuit of second contactor  136  (which is normally open) and activating actuator  160  to open damper  162  to exhaust ventilation system  138 . It also activates exterior strobe/horn unit  146 . 
     Referring now to  FIGS. 8A-8B , front views of an exemplary gas monitoring and alarm system and its relay interface according to the third embodiment are illustrated.  FIG. 8A  further includes a terminal box  164 , which may be optionally used to house wiring terminals. Additionally, as illustrated in  FIG. 8A , primary monitor  102  may optionally be integrated into the front of a box/case that houses relay interface  106 , rather than mounted externally to relay interface  106 .  FIG. 8A  further shows solenoid valve indicator  142  that is included for illustration/demonstration purposes only. Solenoid valve indicator  142  represents the solenoid valve  144 , normally a closed circuit.  FIG. 8A  further includes optional additional exterior strobe/horn unit  146  that may be used in conjunction with the existing horns/strobes of the system as an additional safety mechanism, and optional alarm panel monitoring circuit  158 , both discussed above. 
     Relay Interface Fourth Embodiment 
     Referring now to  FIG. 9 , a block diagram of a relay interface of the gas monitoring and alarm system according to a fourth embodiment is shown. Relay interface  106  comprises terminal bar  132 , first contactor  134 , second contactor  136 , a first transformer  150 , a battery charger  152 , and a backup battery  156 . 
     Terminal bar  132  generates a power supply, fed from power supply  124 , to deliver to first contactor  134 . Terminal bar  132  and first contactor  134  together supply power to exhaust ventilation system  138  and solenoid valve  140 . Terminal bar  132  also delivers power to first transformer  150  and second transformer  154 . 
     First contactor  134  may be a 120-volt definite-purpose contactor (3 Pole), rated at 40 amps at 240 volts. First contactor  134  creates a circuit that normally open and is energized by one of the primary monitor  102  internal relays upon its activation during alarm status. When first contactor  134  is energized, it closes the circuit that supplies power to an external exhaust ventilation system  138 , thereby allowing evacuation of gas when gas concentrations are at or above unsafe levels. First contactor  134  also supplies power to first transformer  150 . First transformer  150  may be a 120-volt to 24-volt stepdown transformer. 
     First contactor  134  is also interfaced with second contactor  136 . Second contactor  136  may be an auxiliary contactor, rated at 40 amps at 240 volts. Second contactor  136  creates a circuit that is normally closed. The closed circuit is deactivated by the first contactor  134  when it is energized by one of the primary monitor  102  internal relays upon its activation during alarm status. Second contactor  136  is used to control power to solenoid valve  140 . During normal operation, gas is allowed to flow freely though solenoid valve  140  that is powered by a 120-volt circuit that is normally closed. However, when high concentrations of gas are detected and primary monitor  102  internal relays are activated, power is supplied to first contactor  134 , thereby closing its circuit that is normally open. When this happens, power is supplied to exhaust ventilation system  138 . Furthermore, when first contactor  134  is energized, it disrupts power to the circuit of second contactor  136  that is normally closed, there by breaking the circuit, closing solenoid valve  140 , and disrupting gas flow. 
     First transformer  150  supplies 24-volt power to battery charger  152 , backup battery  156 , and exterior strobe/horn unit  146 , and actuator  160 . First transformer is wired through second contactor  136 . When first contactor  134  is energized, its circuit (which is normally open) is closed, thereby mechanically closing the circuit of second contactor  136  (which is normally open) and activating actuator  160  to open damper  162  to exhaust ventilation system  138 . It also activates exterior strobe/horn unit  146 . 
     Battery charger  152  converts the 24-volt power from first transformer  150  to 24-volts DC, which in turn supplies power to primary monitor  102 . Battery charger  152  also monitors and trickle charges backup battery  156 . Backup battery  156  may be, for example, a 24-volt battery or two 12-volt batteries. 
     When power is lost (e.g., power supply  124  is cut off) during an alarm status, battery charger  152  engages battery backup  156 , which supplies instantaneous backup power to primary monitor  102 , remote display unit  104 , primary monitor horn  110 , remote display unit horn  128 , primary monitor and remote display unit strobes  120  and  130 , and/or exterior alarm strobe/horn unit  146 . 
     Furthermore, when power is lost (e.g., power supply  124  is cut off) during an alarm status, exhaust ventilation system  138  is automatically shut down, despite that evacuation of the gas via this system is the primary life safety system protocol in the presence of high concentrations of dangerous gases, such as CO 2 . Therefore, battery backup  156  may be used to: (1) maintain power to primary monitor  102 , thus allowing it to continue monitoring concentration of the gas; (2) continue activation of system horns and strobes; and (3) supply power to an optional alarm panel monitoring circuit  158 , which connects the system  100  to an external monitoring service, such as a monitoring company that can alert fire and rescue, that monitors the status of the system  100 . This power backup system allows the system to continue to alert occupants (including emergency responders) that harmful concentrations of the gas are present, even during power outages. It also allows the monitoring service to maintain a connection to the system to monitor the alarm status via the alarm panel monitoring circuit  158 . 
     Referring now to  FIGS. 10A-10B , front views of an exemplary gas monitoring and alarm system and its relay interface according to the fourth embodiment are illustrated. Optionally, the panel monitoring circuit  158  illustrated in  FIG. 10A  may include a data transfer system, which allows the monitoring service to read the concentration of the gas in parts per million (PPM) that is being displayed in real time on the primary monitory  102 . The data transfer may be a 20 milliamp data transfer system.  FIG. 10A  further shows a lightbulb indicator  142  that is included for illustration/demonstration purposes only. Lightbulb  142  represents the exhaust ventilation system  138 , normally a closed circuit.  FIG. 10A  further includes optional additional exterior strobe/horn unit  146  that may be used in conjunction with the existing horns/strobes of the system as an additional safety mechanism, and optional alarm panel monitoring circuit  158 , both discussed above. 
     Relay Interface Fifth Embodiment 
     Referring now to  FIG. 11 , a block diagram of a relay interface of the gas monitoring and alarm system according to a fifth embodiment is shown. The sets of lines (labeled red, green, blue, pink, purple, yellow, orange, brown) show wiring connections between various components of system  100 . It is contemplated that other wiring configurations would be possible. 
     Relay interface  106  comprises terminal bar  132 , a first transformer  150 , a battery charger  152 , a backup battery  156 , a first relay  168 , a second relay  170 , a third relay  172 , and a buzzer  174 . First, second, and third relays  168 ,  170 , and  172  may be ice cube relays. 
     Terminal bar  132  receives power from power supply  124  and supplies a terminal connection location between second relay  170  and alarm panel monitoring circuit  158 . 
     First transformer  150  may be a 120-volt to 24-volt step-down transformer that converts 24-volt AC power to 24-volts DC. First transformer  150  supplies power to primary monitor  102 . It also monitors and trickle-charges backup batter  156 , which may be a 24-volt battery. First transformer  150  supplies 24-volt power to battery charger  152 , backup battery  156 , and first, second, and third relays  168 ,  170 , and  172 . Exhaust system disconnect  165 , which may be a manual circuit breaker (switch), as illustrated in  FIG. 12A , is connected to exhaust system relay  166  and power supply  124 . 
     Through first relay  168 , power is supplied to actuator  160 /damper  162  and an exhaust relay  166 . Exhaust relay  166  is a normally open circuit. When power is supplied to exhaust relay  166 , the circuit is closed, thereby supplying power to exhaust ventilation system  138 . 
     Second relay  170  is constantly energized, which allows for simultaneous normally open circuit and normally closed circuit conditions. Constant power to second relay  170  allows for a normally closed circuit loop for alarm panel monitoring circuit  158 . It also allows for a normally open circuit for buzzer  174 , which may be piezoelectric. 
     When power is lost (e.g., power supply  124  is cut off), the normally closed circuit is opened, which sends alarm panel monitoring circuit  158  into alarm status and may, for instance, alert an external monitoring service, such as a monitoring company that can alert fire and rescue. 
     When power is lost (e.g., power supply  124  is cut off) during an alarm status, battery charger  152  engages battery backup  156 , which supplies instantaneous backup power to primary monitor  102 , remote display unit  104 , primary monitor horn  110 , remote display unit horn  128 , primary monitor and remote display unit strobes  120  and  130 , and/or exterior alarm strobe/horn unit  146 . 
     Furthermore, when power is lost (e.g., power supply  124  is cut off) during an alarm status, exhaust ventilation system  138  is automatically shut down, despite that evacuation of the gas via this system is the primary life safety system protocol in the presence of high concentrations of dangerous gases, such as CO 2 . Therefore, battery backup  156  may be used to: (1) maintain power to primary monitor  102 , thus allowing it to continue monitoring concentration of the gas; (2) continue activation of system horns and strobes; and (3) supply power to an optional alarm panel monitoring circuit  158 , which connects the system  100  to an external monitoring service, such as a monitoring company that can alert fire and rescue, that monitors the status of the system  100 . This power backup system allows the system to continue to alert occupants (including emergency responders) that harmful concentrations of the gas are present, even during power outages. It also allows the monitoring service to maintain a connection to the system to monitor the alarm status via the alarm panel monitoring circuit  158 . 
     Additionally, backup power that is fed by backup battery  156  is triggered to supply power to the line side of second relay  170 , which sends 24-volt power to buzzer  174 . This produces an audible signal that house power has been lost to relay interface  106  and exhaust ventilation system  138 , alerting that the system  100  is now running on 24-volt DC backup battery power. 
     Third relay  172  has a 24-volt powered coil but runs a normally closed 120-volt circuit that powers solenoid valve  140 . In the event that house power is lost, as described above, the relay opens and power is lost to solenoid valve  140 , thereby cutting off gas supply. 
     Referring now to  FIGS. 12A-12B , front views of an exemplary gas monitoring and alarm system and its relay interface according to the fifth embodiment are illustrated.  FIG. 12A  shows a solenoid valve indicator  144  that is included for illustration/demonstration purposes only. Solenoid valve indicator  144  represents the solenoid valve  140 , normally a closed circuit. FIG.  12 A further includes optional additional exterior strobe/horn unit  146  that may be used in conjunction with the existing horns/strobes of the system as an additional safety mechanism, as discussed above. 
     Gas Monitoring and Alarm System with Master Monitor 
     Referring to  FIG. 13A , a block diagram of a gas monitoring and alarm with a master monitor is shown. A gas monitoring and alarm system  200  comprises a power supply  202 , a master monitor  204 , one or more optional slave monitors  206 , and an optional alarm system  208 . Master monitor  204  may be located at a source location  203 . Slave monitor  206  may be located at a remote location  205 . In some embodiments, there may be more than one remote location  205  if there are more than slave monitors  206  being utilized by system  200 . 
     Referring now to  FIG. 13B , a front view of an exemplary gas monitoring system with a master monitor is shown. Power supply  202  supplies power to master monitor  204  and optional slave monitor  206 . In one embodiment, power supply  202  may be configured to supply 24V to master monitor  204 . Master monitor  204  may be coupled to alarm system  208 . Master monitor  204  and slave monitor  206  are discussed in detail below with reference to  FIGS. 14A-E  and  FIGS. 15A-E , respectively. 
     Referring now to  FIGS. 14A-B , a block diagram and a front view of master monitor  202  and master monitor sensor  210  of the gas monitoring system  200  of  FIGS. 13A-13B  are shown. Master monitor  204  receives power from power supply  202 . Power supply  202  may be connected to any power source, such as a wall outlet (e.g., a 110V outlet). Power supply  202  may optionally include a backup battery to be used when the primary power source is lost (e.g., during a power outage) to send backup power to master monitor  204 . 
     Master monitor  204  may be coupled to a master monitor sensor  210 . Master monitor sensor  210  may monitor levels of gas(es) and/or other environmental conditions, such as temperature, etc. In the illustrated embodiment, master monitor sensor  210  is remote from master monitor  204 . However, in other embodiments, master monitor sensor  210  may be integrated into master monitor  204 . It may be desirable for master monitor sensor  210  to be remote from master monitor  204 . For example, it may be desirable to keep master monitor  204  separate from an area holding a gas-containing device (e.g., a CO 2  tank), which would also be where master monitor sensor  210  would be kept. Master monitor  204  may act as an entry pre-warning device such that it can be conveniently observed by a person to determine whether it is safe to enter the area. By way of example and not limitation, master monitor  204  could be kept on a wall immediately outside of a closet, a walk-in cooler, etc. where the gas-containing device is located. 
     Master monitor  204  comprises a display screen  212 , indicator lights  214 , a master monitor horn  216 , and a control logic  217 . Display screen  212  may comprise a digital LCD screen. Display screen  212  may display information about environmental conditions and/or status of gas monitoring system  200 . Master monitor horn  216  may be activated when master monitor sensor  210  senses a condition that exceeds a predefined threshold. Master monitor  204  may further be coupled to master monitor strobe  218 , which may be the same or distinct from the strobe of alarm system  208 . Master monitor strobe  218  may be activated when master monitor sensor  210  senses a condition that exceeds a predefined threshold. Master monitor strobe  218  may be activated simultaneously with master monitor horn  216 . 
     Control logic  217  may be a computer, including a microprocessor, a programmable logic controller, or any other type of suitable controller for receiving sensor information and performing the operations described herein, including controlling horn/strobes  216 ,  218 , display screen  212  and indicators  214 , optionally the display of any slave monitor  206  and indicators thereof, as described in more detail below. Master monitor  204  may be coupled to alarm system  208  (e.g., by a CAT5 cable, CAT6 cable, or other Ethernet/network cable suitable to allow the master monitor  204  to communicate with the remote slave monitor  206 ). Alarm system  208  may be an internal or external alarm system, such as a system that includes a strobe light and/or horn, and may be remote from master monitor  204 . Alarm system  208  may be activated when master monitor sensor  210  senses a condition that exceeds a predefined threshold, and/or when any connected slave monitor  206  triggers an alarm status (as discussed below). Alarm system  208  may, in some embodiments, be connected to a relay interface system (see various relay interface system embodiments, described above) that may be synced to an external monitoring service, such as a monitoring company that can alert fire and rescue services when needed, or it may be connected directly to fire and rescue services. A relay interface system may activate various safety measures to prevent or limit injury once gas levels reach an unsafe level. In yet another embodiment, alarm system  208  may not be connected to any services but may be used merely as an internal alarm system to indicate danger to those in the vicinity. 
     In systems that include slave monitor  206 , master monitor  204  may be coupled to slave monitor  206  (e.g., by a CAT5 cable, CAT6 cable, or other Ethernet/network cable suitable to allow the master monitor  204  to communicate with the slave monitor  206 ). Slave monitor  206  may receive power from master monitor  204  (e.g., 24V), or may receive power from power supply  202 . Slave monitor  206  may be a satellite information repeater and display the measurements made by master monitor  204 . In some embodiments, slave monitor  206  may instead be controlled by a distinct controller separate from the control logic  217 , such that the remote display unit controller controls the operations related to the slave monitor  206  (e.g., operation of its own display screen, indicator lights, horn/strobes, etc.). In some embodiments, the controllers of the master monitor  204  and the slave monitor(s)  206  may be in communication over a network, such as a wireless, cellular, Ethernet, or LAN network, or any other suitable network to facilitate communication between the controllers. Slave monitor  206  is discussed in more detail below with reference to  FIGS. 15A-15E . 
     In some embodiments, master monitor  204  and/or slave monitor  206  may be capable of communicating over a wireless network such as a WiFi network, cellular, or other network which enables master monitor  204  and/or slave monitor  206  to send and receive, for example, status reports and other data to and from remote locations and devices outside of system  200 . 
     Although the term “slave monitor” is used herein, it will be understood that a slave monitor  206  may, in some embodiments, be used as a standalone unit, while in other embodiments, the slave monitor  206  may be required to be used in connection with a master monitor  204 . The terms “slave” and “remote” may be used interchangeably throughout all embodiments described herein to refer to any monitor/unit that is distinct from the “primary” or “master” monitor/unit. 
     Referring now to  FIG. 14C , a front view of the master monitor of  FIG. 14B  is shown. Display screen  212  may include information about environmental conditions sensed by master monitor sensor  210 . For example, display screen  212  may include a temperature indicator  220  and a gas level indicator  222 . Temperature indicator  220  may indicate an ambient temperature of the room/area in which master monitor  204  and/or sensor  210  is placed. Gas level indicator  222  may indicate an ambient gas level (of any gas that is being monitored, such as, for instance, carbon dioxide or carbon monoxide) in the room/area in which master monitor  204  and/or sensor  210  is placed. It will be understood that display screen  212  may comprise other indicators for any other type of condition, including other environmental conditions, or any other relevant status information. 
     Master monitor indicator lights  214  may be used as a quick visual indication of the status of gas monitoring system  200 . For instance, in the illustrated embodiment, master monitor indicator lights  214  comprise four indicator lights  224 ,  226 ,  228 , and  230 . First indicator light  224  may be a steady color (e.g., green), when gas monitoring system  200  is powered on and master monitor  204  is in a “normal” state. For example, a normal state may indicate that master monitor sensor  210  has not sensed any conditions that exceed any predefined thresholds (e.g., gas levels, temperature, etc.). 
     First indicator light  224  may blink and/or turn a different color (e.g., red) to indicate an alarm status. An alarm status may be triggered, for example, when master monitor sensor  210  has sensed that one or more conditions exceed a predefined threshold. In the embodiments shown herein, master monitor sensor  210  detects carbon dioxide (CO 2 ), but it will be understood that the present invention may be used to detect any gas at any concentration, or other environmental conditions (e.g., temperature). Moreover, gas monitoring system  200  may be capable of detecting multiple levels of alarm status based on user input. For example, a first alarm level may be adjustable to a first predefined concentration threshold. In one embodiment, the first predefined concentration threshold may be a concentration of CO 2  at 0.5% or 5,000 parts per million (PPM). A second alarm level may be adjustable to a second predefined concentration threshold. In one embodiment, the second predefined concentration threshold may be a concentration of CO 2  at 1.5% or 15,000 PPM. A third alarm level may be adjustable to a third predefined concentration threshold. In one embodiment, the third predefined concentration threshold may be a concentration of CO 2  at 3% or 30,000 PPM. However, these levels are fully customizable in increments as small as 50 PPM. Thus, the three-level alarm system may allow detection of a gas at varying concentrations, with varying responses to gas detection at each level. In some embodiments, an alarm level of master monitor  204  and/or a slave monitor  206  triggers an internal relay system, which may be coupled to a relay interface. 
     When master monitor  204  senses that it is connected to a slave monitor  206 , first indicator light  224  may illuminate to a steady color (e.g., green). First indicator light  224  may continue to be illuminated at this color as long as it is connected to slave monitor  206 . 
     When master monitor sensor  210  senses a gas at a concentration at or above the first predefined concentration threshold, first indicator light  224  may stay illuminated at the steady color (e.g., green), and second indicator light  226  may be illuminated an alarm status color (e.g., red) and may also blink. Master monitor horn  216  may also be activated and may emit intermittent sounds at a predefined decibel level. Master monitor strobe  218  may also be activated and may begin to flash. 
     If master monitor sensor  210  detects that the concentration of the gas drops below the first predefined concentration threshold, second indicator light  226  may discontinue blinking, master monitor horn  216  may discontinue sounding, and master monitor strobe  218  may discontinue flashing. 
     If master monitor sensor  210  detects that the concentration of the gas continues to rise above the second predefined concentration threshold, second indicator light  226  will continue to blink. Additionally, third indicator light  128  may be activated to an alarm status color (e.g., red) and may begin blinking. Master monitor horn  210  may continue sounding and master monitor strobe  218  may continue flashing, both at an increased tempo. 
     If master monitor sensor  210  detects that the concentration of the gas drops below the second predefined concentration and the first predefined concentration threshold, second indicator light  226  and third indicator light  228  may discontinue blinking, master monitor horn  216  may discontinue sounding, and master monitor strobe  218  may discontinue flashing. If master monitor sensor  210  detects that the concentration of the gas drops below the second predefined concentration but is still above the first predefined concentration threshold, third indicator light  228  may discontinue blinking, but second indicator light  226  may continue blinking and master monitor horn  216  continue sounding, and master monitor strobe  218  may continue flashing, until master monitor sensor  210  detects that the concentration of the gas has dropped below the first predefined concentration threshold. 
     If master monitor sensor  210  detects that the concentration of the gas continues to rise above the third predefined concentration threshold, second indicator light  226  and third indicator light  228  will continue to blink. Master monitor horn  210  may continue sounding and master monitor strobe  218  may continue flashing. Additionally, fourth indicator light  230  may be activated an alarm status color (e.g., red) and may begin blinking. 
     If master monitor sensor  210  detects that the concentration of the gas drops below the third, second, and first predefined concentration thresholds, then fourth indicator light  230 , third indicator light  228 , and second indicator light  226  may discontinue blinking, master monitor horn  216  may discontinue sounding, and master monitor strobe  218  may discontinue flashing. If master monitor sensor  210  detects that the concentration of the gas drops below the third predefined concentration but is still above the first and second predefined concentration thresholds, fourth indicator light  230 may discontinue blinking, but third indicator light  228  and second indicator light  226  may continue blinking and master monitor horn  216  continue sounding, and master monitor strobe  218  may continue flashing, until master monitor  210  detects that the concentration of the gas has dropped below the second and first predefined concentration thresholds. 
     In systems that include at least one slave monitor  206 , indicator lights  214  may additionally indicate the status of slave monitor(s)  206 , such that a user may be able to quickly view the status of master monitor  104  and all slave monitor(s)  206  at a glance. For instance, when master monitor  204  is in a normal state, first indicator light  224  may be a steady color (e.g., green), as described above. If a slave monitor  206  is coupled to master monitor  204 , the indicator lights  224 ,  226  function the same as if only the master monitor sensor  210  is connected (e.g., indicator light  224  is illuminated a steady color, such as green, and indicator lights  226 ,  228 , and  230  may be illuminated an alarm status color, such as red, if an alarm state is triggered) It will be appreciated that although the illustrated embodiments show master monitor  204  coupled to three slave monitors  206 , more or fewer slave monitors  206  may be utilized. More master monitor indicator lights  214  may be included on master monitor display  212  if more slave monitors  206  are included in the system  200 . If fewer than all of the available slave monitors  206  are connected or in use, then fewer than all of the available indicator lights  214  may be utilized. 
     In the event that an alarm status is triggered in one of the slave monitors  206 , the corresponding indicator light  214  may also turn a different color (e.g., red) and/or begin blinking. Therefore, a user who is viewing master monitor  204  may be able to see that one or more monitors  204  or  206  is in a normal state while one or more of the other monitors  204 / 206  is in an alarm state. Master monitor  204  may be programmable to activate an alarm based on user input. For example, the user may program the system to activate an alarm on all (or select) monitors  204 / 206  if any one of the monitors  204 / 206  indicates an alarm status. Alternatively, the user may program master monitor  204  to activate an alarm only on the monitors  204 / 206  where the alarm status was actually triggered based on sensor data. 
     Master monitor display screen  212  may simultaneously display all information about all monitors  204  and/or  206  and their associated sensors (if any). For example, in the illustrated embodiment ( FIG. 13B ), three slave monitors  206  are connected to master monitor  204 . However, the second slave monitor  206  is not connected to a sensor, and therefore no information is relayed to master monitor  204 ; this slave monitor  206  may be used, for example, as a repeater, displaying the level and alarm state of the master monitor  204  at a remote location. The other slave monitors  206  a relaying information to master monitor  204 , including temperature and gas level (e.g., the same conditions being monitored by master monitor  204 ; however, in some embodiments, different conditions may be monitored by different slave monitors  206 ). In the illustrated embodiment (see  FIG. 14C ), the numeral “1” indicates information about master monitor  204 , and numerals “2” through “4” indicate information about slave monitors  206 , respectively. Configuration of the slave monitor(s)  206  is discussed in more detail below. 
     Referring again to  FIG. 14C , each master monitor indicator light  214  may additionally have corresponding toggle buttons  232 A-D. When pressed, toggle buttons  232 A-D may display more detailed information about the monitor  204  program settings. Furthermore, if toggle buttons  232 A and  232 D are pressed and held simultaneously, display screen  212  may display programmable relay concentration thresholds. 
     Toggle buttons  232 A-D may be configured to permit additional programming operations, such as a supervisor setup mode. For instance, in a supervisor setup mode, toggle buttons  232 A-D may be used to change an alarm setup. In one configuration, an individual alarm mode and a common alarm mode are provided. In an individual alarm mode, alarms sound only at the unit (master monitor  204 /slave monitor  206 ) that has detected an alarm level, and at the master monitor if the alarm is at a slave monitor. In a common alarm mode, an alarm sounds at the master monitor  204  and all connected slave monitor(s)  206 , which each display a message indicating which of the connected units has raised the alarm. 
     Toggle buttons  232 A-D may also be used to set up an averaging mode. In this mode, the system compares the lowest alarm level to the average of a preset number of hours&#39; (e.g., eight hours) worth of sensor readings, taken at predetermined intervals (e.g., approximately once per minute). This cannot begin until the unit has accumulated at least the preset number of hours&#39; worth of readings, and until that point, the alarm level is compared to the instantaneous reading as normal. This averaging feature can be turned off or on in supervisor mode based on the user&#39;s needs. 
     Toggle buttons  232 A-D may also be used to configure strobe settings. For example, the strobes of the system may be programmed to activate with third alarm level only, with both the second alarm level and the third alarm level, or with all three alarm levels (alarm level one, alarm level two, and alarm level three), or any similar configurations. In some embodiments, the master monitor  204  and any slave monitors  206  will beep when any alarm level is triggered, regardless of this setting. 
     Toggle buttons  232 A-D may also be used to configure an alarm reset mode. For example, in an automatic mode, as the gas level falls from a higher to a lower alarm level, the alarms will “step down” automatically and cancel when the gas concentration falls below the lowest alarm level. In a manual mode, the alarms will not cancel until manually reset by a user (for example, by pressing a correct combination of toggle button(s)  232 A-D, such as pressing and holding toggle buttons  232 A,  232 B, and  232 C simultaneously), system  200  is reset and all strobes and horns are discontinued from flashing/sounding. In some embodiments, the alarms cannot be reset even while in manual mode so long as there is still a gas concentration higher than one of the preset alarm levels. 
     First indicator light  224  may act as the system status light (e.g., normal state versus alarm state), second indicator light  226  may act as the first alarm status indicator, third indicator light  228  may act as the second alarm status indicator, and fourth indicator light  230  may act as the third alarm status indicator, all as described above with reference to master monitor  204 . 
     Master monitor  204  may additionally comprise a number of ports for accepting connection cables. A first port  234  may accept a cable to connect master monitor  204  to power supply  202 . A second port  236  may accept a cable to connect master monitor  204  to a relay interface system. In systems that include slave monitor  206 , ports  238  may accept a cable or cables to connect master monitor  204  to slave monitor(s)  206 . Ports  236  and  238  may accept, for example, a CAT5 cable, a CAT6 cable, or other suitable Ethernet or network cable. Additionally, a sensor port  239  may accept a cable to connect master monitor  204  to master monitor sensor  210 . Sensor port  239  may accept, for example, a common phone cable or other suitable cable. A strobe port  241  may accept a cable to connect master monitor  204  to master monitor strobe  218 , which may be the same or distinct from the strobe of alarm system  208 . 
     Referring now to  FIGS. 14D-14E , front views of the master monitor sensor  210  of  FIG. 14B  are shown.  FIG. 14D  shows master monitor sensor  210  with a faceplate  240  secured. Faceplate  240  comprises an aperture  242 , to allow for ambient air to flow to the sensor(s). Master monitor sensor  210  further comprises a port  244 . Port  244  may accept a cable to connect master monitor sensor  210  to master monitor  204 . Port  244  may accept, for example, a common phone cable or other suitable cable.  FIG. 14E  is a front view of the master monitor sensor  210  of  FIG. 14D  with faceplate  240  removed. Master monitor sensor  210  may include any number of sensors to sense any type of condition. In the illustrated embodiment, master monitor sensor  210  includes a gas sensor  246  as well as a temperature sensor  248 . Gas sensor  246  may be a nondispersive infrared (NDIR) sensor or any suitable gas sensor. Master monitor sensor  210  relays information gathered from sensors  246 ,  248  to master monitor  204 . 
     Referring now to  FIGS. 15A-15B , a block diagram and a front view of master monitor  204  and slave monitor  206  of the gas monitoring system  200  of  FIGS. 13A-13B  are shown. As previously discussed, slave monitor  206  is coupled to master monitor  204 . In some embodiments, one slave monitor  206  may be utilized. In yet other embodiments, more than one slave monitor  206  may be utilized. For instance, in  FIG. 13B , three slave monitors  206  are shown. 
     To connect master monitor  204  to one or more slave monitors  206 , each slave monitor  206  may be assigned a unique address. For example, removable jumpers may be used to fit on pins of a circuit board to set an address of the slave monitor  206 . In one embodiment, where three slave monitors  206  are possible, the following two-jumper, four-pin configuration may be used to set the address(es) of the slave monitors  206 : to set a first address, no jumpers are utilized; to set a second address, one jumper is fitted to the two left pins; to set a third address, one jumper is fitted to the two right pins; to set a fourth address, both jumpers cover all four pins. It will be understood that this is only one possible configuration, described for illustrative purposes only, and is in no way limiting. Other methods or configurations for assigning a unique address to each slave monitor  206  may be used. 
     Referring again to  FIGS. 15A-15B , master monitor  204  receives power from power supply  202  and each slave monitor  206  may receive power from master monitor  204 . However, slave monitor  206  may be remote from master monitor  204  (e.g., different areas or even different rooms). In an alternate embodiment, slave monitor  206  is not connected to master monitor  204  and is instead connected to its own power source such that it may operate independently as a standalone monitor. 
     Each slave monitor  206  may be coupled to a slave monitor sensor  250 . Slave monitor sensor  250  may monitor levels of gas(es) and/or other environmental conditions, such as temperature, etc. In the illustrated embodiment, slave monitor sensor  250  is external to slave monitor  206 . However, in other embodiments, slave monitor sensor  250  may be integrated into slave monitor  206 . It may be desirable for slave monitor sensor  250  to be remote from slave monitor  206 . For example, it may be desirable to keep slave monitor  206  separate from an area holding a gas-containing device (e.g., a CO 2  tank), which would also be where slave monitor sensor  250  would be kept. Slave monitor  206  may act as an entry pre-warning device such that it can be conveniently observed by a person to determine whether it is safe to enter the area. By way of example and not limitation, slave monitor  206  could be kept on a wall immediately outside of a gas closet or cooler where the gas-containing device is located. In other embodiments, the slave monitor  206  and the slave monitor sensor  250  may be kept in the same room/area, with the slave monitor sensor  250  mounted near the floor, where gas is likely to be concentrated, while the slave monitor  206  is mounted closer to eye-level for convenient viewing by the user. 
     Each slave monitor  206  comprises a slave monitor display screen  252 , slave monitor indicator lights  254 , and slave monitor horn  256 . Slave monitor display screen  252  may comprise a digital LCD screen. Slave monitor display screen  252  may display information about environmental conditions and/or status of slave monitor sensor  250 . Slave monitor horn  256  may be activated when slave monitor sensor  250  senses a condition that exceeds a predefined threshold. Slave monitor  206  may further be coupled to slave monitor strobe  258 . Slave monitor strobe  258  may be activated when slave monitor sensor  250  senses a condition that exceeds a predefined threshold. 
     Referring now to  FIG. 15C , a front view of the slave monitor of  FIG. 15B  is shown. Slave monitor display screen  252  may include information about environmental conditions sensed by slave monitor sensor  250 . For example, slave monitor display screen  252  may include a temperature indicator  260  and a gas level indicator  262 . Temperature indicator  260  may indicate an ambient temperature of the room/area in which slave monitor sensor  250  is placed. Gas level indicator  1262  may indicate an ambient gas level (of any gas that is being monitored, such as, for instance, carbon dioxide) in the room/area in which slave monitor sensor  250  is placed. It will be understood that slave monitor display screen  252  may comprise other indicators for any other type of condition, including other environmental conditions, or any other relevant status information. 
     Slave monitor indicator lights  254  may be used as a quick visual indication of the status of slave monitor  206 . For instance, in the illustrated embodiment, slave monitor indicator lights  254  comprise four indicator lights  264 ,  266 ,  268 , and  270 . First indicator light  264  may be a steady color (e.g., green), when slave monitor  206  is powered on and in a “normal” state. For example, a normal state may indicate that slave monitor sensor  250  has not sensed any conditions that exceed any predefined thresholds (e.g., gas levels, temperature, etc.). 
     Second indicator light  266  may blink (e.g., red) to indicate an alarm status. An alarm status may be triggered, for example, when slave monitor sensor  250  has sensed that one or more conditions exceed a predefined threshold. In the embodiments shown herein, slave monitor sensor  250  detects carbon dioxide (CO 2 ), but it will be understood that the present invention may be used to detect any gas at any concentration, or other environmental conditions (e.g., temperature). 
     As previously discussed, gas monitoring system  200  may be capable of detecting multiple levels of alarm status based on user input. For example, a first alarm level may be adjustable to a first predefined concentration threshold, a second alarm level may also be adjustable to a second predefined concentration threshold, and a third alarm level may be adjustable to a third predefined concentration threshold. 
     When slave monitor sensor  250  senses a gas at a concentration at or above the first predefined concentration threshold, second indicator light  266  may blink an alarm status color (e.g., red) and master second indicator light  226  may also blink an alarm status color (e.g., red). Slave monitor horn  256  may also be activated and may emit intermittent sounds at a predefined decibel level. Slave monitor strobe  258  may also be activated and may begin to flash. 
     If slave monitor sensor  250  detects that the concentration of the gas drops below the first predefined concentration threshold, second indicator light  266  may discontinue blinking, slave monitor horn  256  may discontinue sounding, and slave monitor strobe  258  may discontinue flashing. First indicator light  264  may stay illuminated at the normal state color (e.g., steady green) so long as there is a connection between the master monitor  204  and the slave monitor  206 . 
     If slave monitor sensor  250  detects that the concentration of the gas continues to rise above the second predefined concentration threshold, third indicator light  268  and master third indicator light  228  will begin to blink an alarm status color (e.g., red). Slave monitor horn  256  may continue sounding and slave monitor strobe  258  may continue flashing, both at an increased tempo. Additionally, indicator light  226  may continue blinking. 
     If slave monitor sensor  250  detects that the concentration of the gas drops below the second predefined concentration and the first predefined concentration threshold, second indicator light  266  and third indicator light  268 , as well as master second indicator light  226  and master third indicator light  228 , may discontinue blinking, slave monitor horn  256  may discontinue sounding, and slave monitor strobe  258  may discontinue flashing. First indicator light  264  may stay illuminated at the normal state color (e.g., steady green) so long as there is a connection between the master monitor  204  and the slave monitor  206 . 
     If slave monitor sensor  250  detects that the concentration of the gas continues to rise above the third predefined concentration threshold, second indicator light  266  and third indicator light  268 , as well as master second indicator light  226  and master third indicator light  228 , will continue to blink the alarm status color (e.g., red). Additionally, fourth indicator light  270 , as well as master fourth indicator light  230 , may be activated and may begin blinking an alarm status color (e.g., red). Slave monitor horn  1256  may continue sounding and slave monitor strobe  258  may continue flashing. 
     If slave monitor sensor  250  detects that the concentration of the gas drops below the third, second, and first predefined concentration thresholds, then fourth indicator light  270 , third indicator light  268 , and second indicator light  266  may discontinue blinking, slave monitor horn  256  may discontinue sounding, and slave monitor strobe  258  may discontinue flashing. First indicator light  264  may return to the normal state color (e.g., steady green). 
     Slave monitor  206  may additionally comprise a number of ports for accepting connection cables. A first port  272  may accept a cable to connect slave monitor  206  to master monitor  204 . A second port  274  may accept a cable to connect slave monitor  206  to slave monitor strobe  258 . First and second ports  272 ,  274  may accept, for example, a CATS cable or other suitable cable. A third port  276  may accept a cable to connect slave monitor  206  to slave monitor sensor  250 . Third port  276  may accept, for example, a common phone cable or other suitable cable. 
     Referring now to  FIGS. 15D-15E , front views of the slave monitor sensor  250  of  FIG. 15B  are shown.  FIG. 15D  shows slave monitor sensor  250  with a faceplate  280  secured. Faceplate  280  comprises an aperture  282 , to allow for ambient air to flow to the sensor(s). Slave monitor sensor  250  further comprises a port  284 . Port  284  may accept a cable to connect slave monitor sensor  250  to slave monitor  206 . Port  284  may accept, for example, a common phone cable or other suitable cable.  FIG. 15E  is a front view of the slave monitor sensor  250  of  FIG. 15D  with faceplate  280  removed. Slave monitor sensor  250  may include any number of sensors to sense any type of condition. In the illustrated embodiment, slave monitor sensor  250  includes a gas sensor  286  as well as a temperature sensor  288 . Gas sensor  286  may be a nondispersive infrared (NDIR) sensor or any suitable gas sensor. Slave monitor sensor  250  relays information gathered from sensors  286 ,  288  to slave monitor  206 . In turn, slave monitor  206  relays all gathered information to master monitor  204 . 
     In some embodiments, master monitor  204  and/or slave monitor(s)  206  may additionally include a real-time clock and/or may be configured to log the date and/or time of any alarms that are triggered, which may be useful for reporting or inspection purposes. 
     Gas Monitoring and Alarm System 
     Referring now to  FIG. 16 , a front view of an exemplary gas monitoring system  300  is shown. Power supply  302  may supply power to master monitor  304  and/or one or more slave monitors  306 . In one embodiment, power supply  302  may be configured to supply 24V to master monitor  304 . Master monitor  304  and slave monitor  306  may each be coupled to sensors (e.g., gas/temperature sensors) and may be similar to master monitor  204  and slave monitor  206 , as discussed in detail above with reference to  FIGS. 14A-E  and  FIGS. 15A-E , respectively. 
     Referring again to  FIG. 16 , the system  300  may include relay interface  308 , which may be similar to any of the embodiments of relay interfaces described with reference to  FIG. 3, 5, 7 , or  9  herein. 
     The system  300  may further include additional exterior strobe/horn unit  310  that may be used in conjunction with the existing horns/strobes of the system as an additional safety mechanism, and optional alarm panel monitoring circuit  312 . Both of these components are described in more detail above, with respect to  FIGS. 8A and 7 , respectively. In some embodiments, one or more of the alarm strobes of the system  300  may be daisy chained. 
     The system  300  may further include an exhaust ventilation system  316 . External exhaust ventilation indicator  314  is shown in  FIG. 16   for  illustration/demonstration purposes only. External exhaust ventilation system indicator  314  represents the exhaust ventilation system  316 , normally an open circuit. Exhaust ventilation system  316  may be similar to the exhaust ventilation system  138  described above, for example, with reference to  FIGS. 5, 7, 8A, 9, 10A, 11, and 12A . 
     It will be understood that the primary/master monitors and the remote/slave monitors of the systems described herein may be fully programmable and customizable to suit the user&#39;s needs. For instance, specific alarm responses and alarm levels that differ from the embodiments described above may be programmed based on the user&#39;s particular needs. The example alarm responses/levels are provided for illustrative purposes and are not meant to be restrictive. Additionally, it will be understood that any combination of any of the components of the systems described herein may be used to provide a customized gas monitoring and/or alarm system according to the user&#39;s needs. For instance, the number of monitors (either primary/master or slave/remote) may vary, and some components, such as a relay interface and external exhaust ventilation system, may be included or omitted from a system based on the user&#39;s needs. The various combinations of components if the embodiments of the systems described herein are provided for illustrative purposes and are not meant to be restrictive. 
     Gas Monitoring and Alarm Methods 
     Referring now to  FIG. 17 , a flow diagram illustrating a first method  400  for monitoring gas levels and triggering an alarm system is shown. At a first step  402 , a primary monitor (e.g., primary monitor  102 ) is provided. The primary monitor is configured to monitor a concentration of a gas in an area. At a second step  404 , a sensor of the primary monitor (e.g., gas sensor  108 ) senses that the concentration of the gas exceeds a predefined alarm threshold. At a third step  406 , the primary monitor triggers an alarm status. At a fourth step  408 , the primary monitor activates at least one of a first strobe (e.g., primary monitor strobe  120 ) and a first horn (e.g., primary monitor horn  110 ). At a fifth step  410 , information related to the concentration of the gas and the alarm status is displayed on a remote display unit (e.g., remote display unit  104 ) communicatively coupled to the primary monitor. At a sixth step  412 , the remote display unit activates at least one of a second strobe (e.g., remote display unit strobe  130 ) and a second horn (e.g., remote display unit horn  128 ) when the alarm status is triggered. At a seventh step  414 , a relay interface (e.g., relay interface  106 ) communicatively coupled to the primary monitor activates an exhaust and ventilation system (e.g., external exhaust ventilation system  138 ) configured to evacuate the gas from the area. 
     Referring now to  FIG. 18 , a flow diagram illustrating a second method  500  for monitoring gas levels and triggering an alarm system is shown. At a first step  502 , a master monitor (e.g., master monitor  204  or  304 ) is provided. The master monitor is coupled to a master sensor (e.g., sensor  210 ). The master sensor is configured to sense a concentration of a gas in a first area and send data about the concentration of the gas to the master monitor. At a second step  504 , at least one remote monitor (e.g., slave monitor  206  or  306 ) communicatively coupled to the master monitor is provided. The at least one remote monitor is coupled to a remote sensor (e.g., slave monitor sensor  250 ) configured to sense a concentration of gas in a second area. At a third step  506 , the at least one remote monitor receives data about the concentration of the gas in the second area from the remote sensor. At a fourth step  508 , the at least one remote monitor sends the data to the master monitor. At a fifth step  510 , the master monitor receives the data from the at least one remote monitor. At a sixth step  512 , the master monitor triggers a first alarm status when the concentration of gas in at least one of the first area and the second area exceeds a first predefined alarm threshold. At a seventh step  514 , the master monitor triggers a second alarm status when the concentration of gas in at least one of the first area and the second area exceeds a second predefined alarm threshold. At an eighth step  516 , the master monitor triggers a third alarm status when the concentration of gas in at least one of the first area and the second area exceeds a third predefined alarm threshold. 
     Although the figures may include particular components (e.g., brands and/or product types) for illustration purposes, it is understood that such components may comprise any brand or product type with comparable specifications. 
     It is to be appreciated that the terms “include,” “includes,” and “including” have the same meaning as the terms “comprise,” “comprises,” and “comprising.” 
     Several embodiments have been discussed in the foregoing description. However, the embodiments discussed herein are not intended to be exhaustive or limit the invention to any particular form. The terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations are possible in light of the above teachings and the invention may be practiced otherwise than as specifically described.