Yearbook 2013/2014 - ehedg

32 Particle and VOC emissions, chemical and biological resistance, and cleanability
Hygienic materials suitable for use
in the food industry using the example
of flooring systems
All surfaces in a clean manufacturing environment that are
in contact with the ambient air are capable of contaminating
it. Consequently, they significantly affect the attainment
and maintenance of a required degree of cleanliness. For
example, if process water accumulates in the joint of a
flooring system sealed with poor quality sealing material, any
mould spores present could flourish there due to the good
local growing conditions (humidity, temperature, nutrients)
and become a major source of infection. If a material
corrodes as a result of the effect of an aggressive cleaning
agent, it not only loses its required material properties but
may become a dangerous source of particulate emissions.
Chemical influences may cause a flooring material to
become brittle. If mechanical action is subsequently applied
(transport rollers of a heavy preparation tank, etc.), cracks
could form, representing a microscopic hazard because it
would be impossible to remove or inactivate effectively any
microorganisms accumulating in the cracks. Among others,
this aspect was considered in the requirements of the EU-
GMP Guideline Annex 1 illustrated in Figure 4:
Extract from EU-GMP-guideline Annex 1:
» … in clean areas, all surfaces should be smooth, imperious and unbroken in
order to minimize the shredding or accumulation of particles or
microorganisms and to permit repeated application of cleaning agents and
desinfectants where used … «
» … The manufacture of sterile products is subject to special requirements in
order to minimize risks of microbiological contamination, and of particulate
or pyrogen contamination.«
Particle
Biol. Resistance and
Microbizidity
Cleaning and
Chem. Resistance
Figure 4. Extract from EU-GMP Annex 1 with derivable material
requirements.
Therefore, flooring systems installed in a hygienic
manufacturing environment need to be resistant to the
chemicals used in cleaning and disinfection agents.
Microorganisms may not colonise there or interact with them.
Surfaces must be thoroughly cleanable. No substances may
migrate from materials to the product and the material may
not host any form of contamination. In some industries,
material surfaces are treated with an antimicrobial agent.
In such cases, it is not only important to be sure that the
antimicrobial coating functions in practice but also that the
material does not represent a hazard to human health in any
way.
Due to the large surface area and associated contamination
risk of flooring systems, they are now discussed in more
detail. First of all, the under-surface of a flooring system
must be permanently sealable. Liquid residues from a
previous cleaning or disinfection process may remain on the
surface for a long time, making it extremely important for the
system to be highly resistant to the chemicals used. To be
able to clean edges and corners effectively, flooring must be
laid so that it extends upwards to cover the bottom section
of walls. The mechanical properties of the system must be
designed to prevent damage from occurring as a result of
typical stresses (e.g., rollers of transport trolleys, high point
loads). To generally aid cleanability, roughness levels must
be kept as low as possible. However, the need for a nonslip
coating, if required, may not be forgotten in the process.
Where possible, the transmission between floor and wall
systems should be seamless.
The biomaterial regulations in Annex 2 state that, for all
protective categories, surfaces are to be impermeable to
water and easy to clean. From Level 2 upwards, biomaterial
regulations require adequate resistance to acids, alkalis,
disinfection agents and solvents. 8
In the case of reactive systems (e.g., epoxy resin floors),
care must be taken to ensure that the outgassing of organic
contamination is kept to a minimum in order to protect
employees and, if sensitive processes are concerned, also
the product. No critical airborne particulate contamination
may be generated on subjecting the flooring system to
tribological stress (e.g., rollers, stress due to walking,
etc). Comparative tests need to be carried out on a wide
range of materials to determine outgassing behavior and
particulate emission due to tribological stress, and the
results appropriately classified. 9,10 It must be possible to
clean flooring systems effectively using dedicatedl cleaning
methods and agents.
Material and methods:
Comparative tests to classify materials
Particulate emission
If a material is subjected to mechanical stress due to
friction from another material, material abrasion in the form
of particle generation occurs. This also can be caused by
sliding friction from rollers or static friction from walking over
a flooring system wearing shoes. To obtain comparative
information about particulate emission from various flooring
systems due to tribological stress (friction), a special
tribological test bench has been constructed (Figure 5). It is
operated in a Class ISO 1 reference cleanroom to eliminate
measurement errors caused by potential foreign particles
in the environmental air. 2 In the comparative classification,
only sliding friction is considered. The counter sample
used in the tests is a standardised polyamide-6 roller that
simulates the sliding friction caused by transport rollers.
Both applied force and angular velocity are kept constant.
The laminar unidirectional airflow with a velocity of 0.45
m/s, which flows from the cleanroom ceiling to the raised
floor in accordance with ISO specifications for a Class 1
cleanroom, ensures that particles generated during the test
are transported downwards in a vertical direction towards
the sampling probe installed downstream that detects
the airborne particles (Figure 2). Using the principle of
scattered light, a particle counter detects all particles with
a diameter >0.2 µm and classifies the number of particles
into predefined particle size channels according to their
size. To take single events appropriately into account, the
test is performed for a minimum of one hour. On cumulating
the data and transforming coordinates, a result is obtained
that gives an assessment of the test material with regard to
particulate abrasion due to tribological stress. The procedure