1. A modular heating, ventilation, and air conditioning system for providing positive pressure to an interior of a positive pressure facility, wherein the system comprises: a. an enclosure for securing to an exterior of the positive pressure facility, wherein the enclosure comprises: (i) a base; (ii) a condenser compartment mounted to the base, wherein the condenser compartment has: 1. an air inlet grill covering a side of the condenser compartment; and 2. an air venturi mounted to a condenser coil in the condenser compartment, wherein the air venturi is configured to pull air through the air inlet grill and across the condenser coil using fan blades mounted to a condenser motor in the condenser compartment; (iii) an evaporator motor compartment in the enclosure comprising at least one evaporator motor mounted therein; (iv) an evaporator compartment in the enclosure comprising: 1. an evaporator fan connected with each evaporator motor; 2. an evaporator coil mounted in the evaporator compartment and configured to receive a refrigerant to cool fresh air and form conditioned air; 3. a refrigerant liquid line connected with the evaporator coil; 4. a refrigerant suction line connected with the evaporator coil; 5. a thermostatic expansion valve connected with the refrigerant liquid line; and 6. an evaporator compartment drain configured to allow a condensate from the evaporator coil to exit the evaporator compartment; and (v) a compressor compartment connected with the evaporator motor compartment, wherein the compressor compartment comprises: 1. a compressor mounted in the compressor compartment and connected between the refrigerant suction line and a refrigerant discharge line; 2. a high pressure transducer connected with the refrigerant discharge line; 3. a low pressure transducer connected with the refrigerant suction line; 4. a shut off valve connected with the refrigerant discharge line; 5. a hot gas bypass valve connected with the refrigerant suction line; and 6. a refrigerant shut off valve connected with the hot gas bypass valve; b. a fresh air intake section formed in the enclosure and configured to draw in the fresh air from outside of the enclosure into the evaporator compartment; c. a heater compartment in the enclosure comprising: (i) at least two fin heaters connected with a power supply; (ii) a conditioned air temperature sensor configured to monitor a temperature of the conditioned air; and (iii) a plurality of resistive temperature detectors, wherein each resistive temperature detector is connected with and monitors a temperature of one of the fin heaters; and d. an enclosure extension attached to the enclosure, wherein the enclosure extension is configured to protrude through the exterior and into the interior of the positive pressure facility, and wherein the enclosure extension comprises: (i) a return air compartment comprising: 1. a plurality of opposed blade dampers; 2. a humidistat; and 3. a return air resistive temperature detector; (ii) an electrical compartment connected with the return air compartment, wherein the electrical compartment comprises: 1. an electrical control box configured to receive power from the power supply, wherein the electrical control box comprises a relay, a connector, and an overload protection circuit for the at least one evaporator motor, the condenser motor, and the compressor; 2. a process control unit connected with the electrical control box for controlling electrical flow through the electrical compartment, wherein the process control unit is in communication with: the evaporator coil, the evaporator fan, the at least one evaporator motor, the condenser coil, the fan blades, the condenser motor, the compressor, the low pressure transducer, the high pressure transducer, the conditioned air temperature sensor, the plurality of resistive temperature detectors, and the return air resistive temperature detector; and 3. a pressure transducer for determining a differential pressure between a pressure outside of the positive pressure facility and a pressure of the interior of the positive pressure facility, wherein the pressure transducer is connected with the process control unit; and (iii) a human machine interface connected with the process control unit comprising a display configured to present: 1. real-time temperature values; 2. real-time humidity values; 3. real-time building pressure; 4. a home control button; 5. a control button; 6. a health control button; 7. a set points control button; 8. a values control button; 9. a heating, cooling, and dehumidifying indicator; 10. an operating indicator; 11. a building pressure OK indicator; 12. a system OK alarm; and 13. a time.