A process and apparatus to preclude unfiltered atmospheric gases and the products of human respiration including carbon-dioxide (CO2) with carbon-14 (14C) from contaminating greenhouse atmospheric gases which has utility in growing agricultural products with a reduced abundance of 14C are disclosed. Agricultural products with reduced 14C content can be grown in greenhouses with filtered atmospheric gases for the benefit of reducing harmful damage to human DNA. Agricultural production in greenhouses still requires humans to plant, maintain, and harvest crops in many cases. The process and apparatus allow for humans to access, work, and operate in these controlled environments without contaminating the atmospheric gases and agricultural products therein with respiration products and unfiltered atmospheric gases containing radioactive 14C.