Information from the VSD

Risks of sprout inhibition via the hot fog process

Besides optimized storage management, sprout inhibition of potatoes is an indispensable component for maintaining the quality of stored potatoes. In connection with the frequently used hot fogging of sprout inhibitors, however, fires have repeatedly occurred in the past in the warehouses in question. The Dethlingen Test Station has takes these as an opportunity to point out possible dangers.

In principle, a distinction must be made between two types of hot fogging equipment: Through gasoline-powered devices, a gasoline/air mixture is burned in a combustion chamber provided for this purpose. The resulting hot air stream is discharged from the unit through a fog pipe. Electrically operated appliances use a fan, with an electric heating element coupled to it, to generate a hot air stream. In both methods, the germination inhibiting agent is now injected into the hot air stream through a nozzle in the fog pipe, so that a fine mist is produced, which is evenly distributed in the warehouse by the ventilation system.

When using hot fogging devices, regardless of whether the device is petrol or electrically operated, there is a general danger if the fogging temperature is not or cannot be adjusted to the flash point of the preparation to be applied. In the worst case, this can lead to an ignition of the escaping fog stream. Therefore, before use, check whether the device and the preparation may be used in the desired combination. For example, some preparations may only be applied with electrically operated hot foggers. At present, one manufacturer generally advises against the use of his gasoline-powered devices for sprout inhibition in potatoes.

Great importance is also attached to the selection of the location of the hot fogging unit. The unit should be easily accessible, safe and stable outside the storage room. No flammable objects, such as parts of the insulation or cobwebs, may be located around the unit or in the area of the injection opening (outside and inside the storage room). Furthermore, nebulization must only be carried out by qualified personnel using a device with a valid inspection sticker and under constant supervision.

With regard to the safety aspect, two further particularly dangerous operating conditions can occur with gasoline-operated hot fogging units, unlike electrically operated units:

Case 1: The gasoline tank is completely emptied during the nebulization process. In this case, the hot exhaust gas flow, which discharges the preparation from the fog tube, is interrupted. However, the supply of the applied plant protection agent, which is conveyed into the fog tube by a slight overpressure in the storage tank of the preparation, does not stop automatically with all devices. In this case, the preparation, now no longer being discharged, can get into the still hot combustion chamber and might ignite there. For safety reasons, the devices are usually designed in such a way that the preparation container can be completely discharged when a full tank of gas is used. Therefore, the unit must be sufficiently filled before starting the treatment.

Case 2: The container of the preparation is completely emptied during operation. In this case, the cooling effect of the sprayed preparation is interrupted. Depending on the unit type, a small pilot flame may escape from the fog tube even if the hot fogger is set correctly during operation without nebulising agent. If deposits of the applied preparation have formed in the area of the injection opening during the nebulization process, they will be ignited. A reduction of the preparation flow can also occur due to dropping temperatures. Since the fluidity of some preparations decreases when they cool, it is essential to store them at room temperature before use and to protect them from cooling during application.

Electrically operated devices for hot nebulization are more expensive than gasoline-operated devices, but in practical use they offer greater flexibility in the selection of the agents to be used as a result of more precise temperature control. As a further advantage, no additional carbon dioxide in the form of exhaust gases is introduced into the warehouse with these devices. The most important facts in brief:

  • The application and safety instructions for the preparations and nebulization devices used must be strictly observed.
  • Nebulization must only be carried out by qualified personnel and under constant supervision.
  • Devices for hot nebulization are subject to the test obligation for plant protection devices and must have a valid test badge.
  • Set up equipment safely outside the storage room, observe user protection and remove flammable objects, keep fire extinguisher ready.
  • Fill up the unit sufficiently before starting treatment.
  • Store preparations at room temperature before treatment and protect against cooling during treatment.

For more information:
Deutscher Kartoffelhandelsverband e.V. (DKHV)
Schumannstr. 5, D - 10117 Berlin
Tel.: 030 / 754524-67

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