Johnson’s LP Gas CO2 Generator is a ceiling‑hung, liquid‑propane model built by Johnson Gas Appliance Co. for greenhouse enrichment. The Classic unit fertilizes up to 4,800 sq ft and produces about 72 cubic feet of CO2 per hour (approximately 8.25 lb/hr) at 60°F, with burner output adjustable from 20,000 to 60,000 BTU/hr. LP units require the brand’s 115V/24V, 40 VA transformer for operation; an optional photo‑sensor CO2 controller is available and includes the transformer. The generator measures roughly 18 inches in diameter by 20 inches high and weighs about 25 lb. Safety features include a 24‑V gas valve and automatic shut‑off on flame failure. CO2 production is slightly lower on natural gas. Typical installation hangs the unit overhead and needs no ductwork.