A store with non-positive ‘overhead throw’ air delivery system.


CIPC application in box stores

Effective treatment of potatoes stored in boxes requires a range of approaches depending on the type of storage system being used. CIPC treatments must be carried out using ACTIVE (i.e. fan assisted) RECIRCULATION.

Positive ventilation

In stores with true positive ventilation (e.g. letterbox and lateral suction/Aspire systems), the store ventilation system should be used to recirculate CIPC fog.  As with bulk stores this should be done with fans operating at low speed, controlled through an inverter (variable frequency drive). Any refrigeration system should be by-passed or sealed off to eliminate the risk of the coil becoming blocked. Recirculation should take place for the duration of the application and until the fog has cleared.

Non-positive ventilation (‘overhead throw’ stores)

Most box stores in GB are of the ‘overhead throw’ type and do not have positive ventilation. With this system, air is displaced by fans above the boxes and moves around the crop rather than through it. To continue using CIPC in these stores, corrective action is needed to ensure active recirculation can take place.

Open suction

Creating an open suction system is a cost-effective way to provide ‘active recirculation’ for overhead throw box stores. Using an existing plenum chamber, creating a new one at the end of the store from scratch or by fitting an ‘air divider’ curtain, it is possible to close off any short-circuit back to the fan. The system then relies on the open pallet slots within the block of boxes to convey the CIPC to the target. Note that, as the slots remain open, it is still not positive ventilation. Active recirculation is achieved using a slow speed fan (typically running at 25-50% of normal ventilation speed) to draw the chemical along the pallet slots. This can be a speed-controlled main ventilation fan or a dedicated fan fitted for the purpose. See CIPC APPLICATION: A Store Owner's Guide for more details.

Central plenum

A plenum is an enclosed space for the purposes of distributing air. Creating a plenum within a box stack can be a useful way of distributing CIPC fog, as it allows the treatment to be introduced directly into the box pallet slots (see Fig. 1). Plenums are created in the centre of a block of boxes by leaving a gap of 450-600 mm wide and covering it with a light tarpaulin cover. CIPC is introduced via a port installed adjacent to the plenum; liaise with your fogging contractor over these arrangements and before cutting holes in the building fabric. Health and safety regulations must be complied with when fitting covers to plenums. If this is problematic, use open suction instead. A secondary fan within the plenum is then used to provide ‘active recirculation’ of the fog through the stack See CIPC APPLICATION: A Store Owner's Guide for more details.

New stores

Where the construction of new stores is being considered and it is anticipated these could require application of CIPC, the incorporation of positive ventilation is strongly recommended. It is anticipated that the extent to which CIPC can be used in overhead throw stores may be limited in the future.

 CIPC applicationplenum in an OHT box store

Figure 1: CIPC application plenum in an OHT box store made by covering an inspection corridor through a block of boxes.

A fogging port is installed to align with an inspection corridor, through blocks of boxes. The area between blocks is then sheeted over, from ground level, over the top and back down the opposite side, leaving a gap into which CIPC is fogged. Ensure health & safety regulations are complied with during installation, and where access to top boxes is required.