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• 12. Ventilation Systems

12. Ventilation Systems

All food processing operations should operate at a positive air pressure with respect to the outside environment to prevent contamination being sucked into the building from outside. Critical hygiene areas should be at a higher pressure than areas where raw materials are handled or stored.

Positive air pressure can be achieved by forcing fresh air into the processing area. Incoming air will need to be filtered to remove contaminating particles. There should be a documented filter maintenance programme in place, with a record kept of all filter maintenance carried out. Filters will need to be checked, cleaned and replaced at frequent intervals. Intakes should be upwind from the prevailing wind, exhaust vents, inwards goods and rubbish disposal sites.

The volume of incoming air must be greater than the volume removed by exhaust vents and extractor fans to maintain a positive pressure in the processing area.

Condensation on walls and ceilings is an indication that the ventilation system is inadequate.

Cooling systems

• Condensate dripping from cooling systems has been identified as a possible source of Listeria in a number of food processing operations.

Therefore, it is essential that all drainage ducting from air-handlers and condensers is piped directly into the drains and not on the floor or ground.