source: https://ors.od.nih.gov/sr/dohs/Documents/cold-room-mold.pdf
The axonometric diagram below shows the cooling process of a cold room. Most cold rooms have a closed ventilation system. The air remains circulated in the room. Cold air blows out from the evaporator. As it circulates through the room, it relatively warms up, brought back into the evaporator, and chilled once more before starting the cycle anew.
Opening the door is usually the only way fresh air gets into the space. The incoming warm air enables condensation on cold surfaces, which is a suitable condition for the growth of molds.
Mold spores are all around us, in the air we breathe, on surfaces, in the indoors and outdoors environments, except on the North and South Poles. Mold plays an important ecological role breaking down of dead organic matter. Mold needs a surface, a source of nutrients and moisture to settle. In cold rooms warm air condensing on cold surfaces provides a sufficient basis for mold growth.
Mold appears not only on the inner walls of cold rooms and storages, but also on the surface of stored fruit and vegetables. The problem is comprehensive, a comprehensive defense must be envisaged. We recommend the defense with our R-FILTER devices to execute, using ozone gas and UV-C light.
We hang so-called UV lamp frames on the ceiling of the storage room at a distance of 2-3 meters from the evaporator fans taking care to create the least resistance to the circulated air. We use UV lamps that also generate ozone. The combination of UV-C light and ozone is a double blow for mold spores in the air. By circulating the air, the ozone gas reaches every corner of the warehouse and also the surface of the stored fruit or vegetables to prevent mold growth.
Ozone gas is also suitable for removing ethylene released during the ripening of stored products in fruit and vegetable storage rooms. If this gas accumulates, fruits and vegetables ripen quickly, causing quality deterioration and a reduction in shelf life.
The UV-C light emitted at 254 nm proves to be extremely effective in killing molds (Aspergillus niger, Aspergillus fumigatus, Microsporum canis, Epidermophyton floccosum, Trichophyton rubrum), as the entire environment using the lamps is covered by the light, which enables the disinfection of a large air mass. The radiation dose necessary for destruction is guaranteed by the fact that the evaporator fans run 24 hours a day, and the R-FILTER devices run parallel to them, so the mold spores receive multiple irradiations during circulation. Personnel walking on the bottom of the cold room are not directly exposed to UV-C light due to the design of the device. UV light emitted at 185 nm produces ozone, which destroys mold. Ozone gas in the air can travel to places where UV-C light cannot reach directly. Ozone has a sharp pungent and chlorine-like odor. Its oxidizing effect strongly irritates the respiratory tract. The permissible workplace ozone exposure limit values in an international comparison:
- 0,1 ppm (0,2 mg/m³) for an 8-hour workday
- 0,2 ppm (0,4 mg/m³) max. for 15 minutes
To ensure that the ozone concentration required to kill mold is introduced, the evaporator fans and the R-FILTER devices connected to them are in operation 24 hours a day. In this way, the mold spores are exposed to multiple ozone loads during the circulation and the ozone gas continuously reaches all surfaces in the warehouse.
In the storage, use that much ozone-producing UV frames so that the ozone concentration at the bottom of the storage does not exceed the 0.1 ppm concentration during the 24 hours of the day. At such a concentration, the storage personnel can use the entrance, since the concentration does not exceed the level allowed for them for an 8-hour workday. For the sake of safety, an ozone concentration meter must be placed at a typical place at a height of 150 cm, which switches off the ozone-generating lamps above 0.1 ppm. It is important to have a forced connection between the fans of the evaporator and the R-FILTER devices. If the fans of the evaporator are not working, the devices must not work either!
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