The concept “Controlling the atmosphere”
Cold stores alter the temperature inside an enclosed chamber through the use of refrigeration. To save operating costs of the cooling equipment, insulation as a thermal barrier is used to minimise external heat ingress. Depending on the product types stored, the cooling is distributed inside the chambers using fans which circulate cool air – in case of frozen temperature ranges, the cold air need only shield and isolate the cargo from the exterior peripheral walls & other heat ingress.
In case of living fresh produce, the cold air must additionally envelope each individual product piece and penetrate interstitial space in storage to evacuate other gases & heat produced due to respiration. This is ordinary storage and does not involve tampering with natural atmospheric composition.
Controlled atmospheres are essentially those which deviate from the normal air composition of 21% oxygen, 78% nitrogen and 380 ppm of carbon dioxide (Other gases present are normally too small a concentration to have a prime effect on stored produce). Controlled Atmosphere cold stores best understood as cold storages designed and fitted with additional equipment such as to actively change and control the atmospheric content inside the closed chamber.