The Johnson LP Gas CO2 Generator is a ceiling-hung, liquid‑propane model designed to enrich greenhouse air with carbon dioxide. Official specs list a burner range of 20,000–60,000 BTU/hr on LP gas, delivering about 72 cubic feet of CO2 per hour (approximately 8.25 lb/hr) at 60°F. One unit is rated to fertilize up to 4,800 square feet at 1,500 ppm assuming one air change per hour; output is slightly lower on natural gas. The unit includes flame‑safety shutoff and a 24‑V gas valve, and it requires a separate 115‑V/24‑V transformer to operate; an optional PPM controller is available. The housing measures roughly 18 inches in diameter by 20 inches high and is made by Johnson Gas Appliance Co. in the USA.