in the exhaust hood, the exhaust air is pushed through the duct
and not pulled out. By pushing vapors, fumes, etc. through that
duct, the system puts the exhaust duct under positive pressure,
which can force dirty air back into the room through holes and
gaps in the duct work.
Hygienically Designed Lighting
Lighting must illuminate horizontal and vertical working
surfaces evenly, without causing glare and at an intensity of
about 300–500 lux at normal working height. Walls and ceilings
should be light-colored because that permits fast detection of
dirt and soil on their surfaces. In contrast, dark-colored walls
and floors require additional lighting.
Preference should be given to lighting mounted on ceilings
rather than on walls, because process equipment, storage racks,
etc. can form shadows that make cleaning and inspection of
floor, walls or ceilings difficult. For the same reason, overhead
piping may not obstruct lighting.
Selected lighting should produce little heat and UV light to
prevent attraction of insects. Because high-intensity discharge
lamps (metal halide, and high- and low- pressure sodium lamps)
have high penetration depth, they are used as high-bay lighting
in warehouses; fluorescent luminaires are preferred as low-bay
lighting, giving good illumination with less glare when covered
with a prismatic cover or opalescent diffusing panel.
Lighting systems and their supports may not create horizontal ledges, legs or surfaces. To avoid projections that can accumulate dust, they can be built into the ceiling or wall with a
hermetically closed seal, a procedure that is typical for cleanroom areas where lamps are changed via the technical area.
Hygienic Supply and Application of Electricity
In zone M areas, installing individual cables or multiple cables of small diameter, sharing the same route, in conduits is
recommended. When two or more cables partly share a common route but go to different termination points, the creation
of unsealable openings that allow the cable(s) to enter or exit
the conduit is possible. However, this practice is only recommended for short distances. For long distances, straight line,
non-bundled electric cables should be mounted on wire trays,
preferably separated from each other. Vertical cable trays are less
prone to dust accumulation, and are more accessible for inspection and cleaning. The use of horizontal racks for electrical cabling should be minimized, or they should be protected by a
removable lid or installed vertically (on their side) to minimize
horizontal surfaces.
When two or more cables partly share a common route, but
go to different termination points, unsealable openings allowing cable(s) to enter or exit the conduit should be avoided.
Conduits should be suitably sealed at both ends with a proprietary cable/sealing gland where a cable does pass through. In
the food contact and splash areas, cables can also be protected
from dirt, penetrating liquid and damage by encapsulating
them in hermetically closed cable housings. However, the use
of pipe rather than conduit should be discouraged because of
the difficulties in maintaining the integrity of the piping system
at cable entries and exits. Cable mounting in pipes still creates a
hollow body and hence a hygienic risk.
tight cabinets or field boxes with all connections made at the
bottom. Connections of cables and wires to housings must be
sealed. The enclosures should be spaced away from equipment
or walls and should be provided with an easily drainable 30°
top roof. The heat generated by the electrical installations
within these enclosures, and concomitantly the dust that penetrates the electrical installation during its cooling by means of
fans, should be ventilated toward a technical area or a central
ventilation system.
Control Panels
Control panels with high ingress protection rating should be
provided with hygienically designed control and indicator devices. However, the more modern and hygienic membrane panels
or touch-screen display panels now often replace these older,
non-computer-based control panels.
Conclusions
Many food manufacturers only make use of the classic food
preservation approach to control food safety. In the past two
decades, however, the European Hygienic Engineering & Design Group has demonstrated that hygienic design of food process equipment and factories can contribute significantly to
enhanced food safety. Hygienic food factory design starts with
the selection of an appropriate location and the application of a
hygienic building concept that prevents the entry of pests. The
factory layout must permit the correct flow of materials, waste,
air and personnel without compromising food safety as well as
the installation of hygienic zones that offer maximal protection
to the food produced. Process equipment and process and utility piping must be designed from food-grade materials that are
compatible with the food product produced and the cleaning
agents and disinfectants applied to sanitize the production environment. To avoid the introduction of new contaminants,
equipment and piping must be hygienically integrated within
the factory’s premises. Walls, ceilings and floors must have an
appropriate finish, lighting must provide sufficient illumination
and drains should guarantee proper drainage to facilitate cleaning and to maintain hygienic conditions within the factory. The
aim of this article is to serve as an introduction to proper hygienic food facility design. n
Frank Moerman received his M.Sc. in bioengineering from the
University of Ghent in Belgium. In 2002, he became a member of
the European Hygienic Engineering and Design Group (EHEDG)
responsible for Belgium. More about EHEDG can be found at
www.ehedg.org.
Resources:
Lelieveld, H.L.M., M.A. Mostert, J. Holah and B. White. 2003. Hygiene
in Food Processing: Principles and Practice. Cambridge: Woodhead
Publishing Ltd.
Lelieveld, H.L.M., M.A. Mostert and J. Holah. 2005. Handbook of
Hygiene Control in the Food Industry. Cambridge: Woodhead
Publishing Ltd.
Lelieveld, H.L.M. and J. Holah. 2011. Hygiene Control in the Design,
Construction and Renovation of Food Processing Factories.
Cambridge: Woodhead Publishing Ltd., in progress.
