Cleaning regimes: see what is missing

A new cleanroom tool makes invisible hazards visible and highlights areas that have been overlooked during the cleaning and disinfection process. UV light is emitted from a torch and excites the electrons in the atoms or molecules of the particles in question. These absorb the energy from the torch temporarily and emit it as light, making visible particles that cannot be seen by the naked eye.

Figure 1: The absorption and emission processes

A new tool has been developed that can be used to demonstrate the effectiveness of cleaning regimes and the capabilities of cleaning personnel. This report by Dominic Heckmann, trainer in the Manufacturing Science and Technology (MSAT) Department Roche Diagnostics, and James Tucker, European Portfolio Manager for Shield Medicare, summarises the validation of the tool’s effectiveness.

The Klercide UV Validation Torch is a new cleanroom tool that makes invisible hazards visible. The ability to highlight areas that have been overlooked during the cleaning and disinfection process enables organisations to solve problems before they become costly.

The torch is used for process improvements – for example, to highlight changes that need to be made to transfer disinfection procedures – and can be a valuable technician training aid for demonstrating correct surface and disinfection techniques and their effectiveness.

Figure 2a: Background surface used for testing the effect of background lighting level, without the use of the torch

There are already a number of ways of ensuring that a cleanroom is clean and that standard operating procedures are effective. These include visual inspection, particulate and microbiological monitoring and residue measurement. The Klercide UV Validation Torch offers the opportunity to move beyond these methods with a highly sensitive instant visual result.

UV light is emitted from the torch and excites the electrons in the atoms or molecules of the particles in question. The atoms or molecules can harness the energy from the torch (absorption) only temporarily, and they quickly release this additional energy as light (emission).

It is the released light energy from the atoms or

Figure 2b: Background surface used for testing the effect of background lighting level, with the use of the torch

molecules of the particles that makes the particles visible to the naked eye when previously they could not be seen, thereby making the invisible visible. Figure 1 shows the absorption and emission process in action.

Five separate parameters were tested to verify the robustness of the UV Torch’s detection process. In addition tests were carried out with trained operators to verify the effectiveness of their procedures and with operators undergoing training to verify the effectiveness of the training.

The five parameters were:

Particle size: Latex particles of varying sizes (as used for validation of particle counters) were diluted in water and applied to a surface to determine the limit of detection.

Background lighting level: Tests were carried out at various background lighting levels to determine at what level the particles ceased to be visibly discernable and the optimum detection of surface contamination could be achieved.

Figure 3: Test set up for measuring the effectiveness of the UV Torch at varying distances from the surface

Background surface material: A number of different background surfaces were used to determine if their light absorption or contrast properties had an effect on the visibility of the emitted light.

Distance from UV source: Tests were carried out with the UV source (Torch) at varying distances from the surface to determine at which point the source became too weak to detect particles.

Fluorescence of different materials: It is hypothesised that due to the way the Torch works the fluorescence of a particle will be dependent on the density and homogeneity of the material.

Test method

Materials: latex particles (0.7µm/3.0µm/30µm/50µm); water (filtered); conical flask (glass) 100ml particle free; microscope slide (glass); Eppendorf pipette; drying oven; stainless steel plate 10 x 10cm; plexiglass plate 10 x 10cm; Makrolon (polycarbonate) 10 x 10cm; Pharma Terrazzo 10 x 10cm; Hypalon (glove material) 10 10 x 10cm; RODAC plate (25cm2), LUX2 – measuring instrument; neon tube (adjustable); IPA wipes; torch mounting plate; metre rule; various materials as shown in Table 2; Klercide UV Validation Torch.

Particle size: Individual suspensions were made in the 100ml conical flask at a concentration of 0.25g of each size of particle in 3.75ml of water. The suspensions were applied to the microscope slide and fixed with a secondary slide on top of this. The slides were dried in a drying oven for 1hr at 45°C. On completion of the drying process the slides were examined with the aid of the torch for visual detection of the particles and the results recorded.

Background lighting level: The LUX detector was set up underneath the adjustable neon light tube to measure the amount of background light. The stainless steel plate was marked by contact from a TSA RODAC plate. The lighting level was increased gradually from 0 LUX (the lowest level). The steel plate was examined for residues detectable with the UV Torch at the various LUX levels and the results recorded.

The surface used for this experiment with and without the use of the Klercide UV Validation Torch can be seen in Figure 2. The results are recorded in Table 1.

Table 1: Optimal background light
LUX
Visible
50
Yes
100
Yes
150
Yes
200
Yes
250
Yes
500
Yes
1000
Yes
1500
With difficulty
2000
With difficulty
2100
No
2500
No

Background surface material: A range of commonly encountered cleanroom surface materials were prepared by removing any particles with a high grade pre-impregnated IPA wipe. A 50µm particle suspension was dispensed onto these surfaces in a unidirectional airflow bench. The samples were dried for 1hr at 40°C in the drying oven. The surfaces were then examined with the UV Torch. The results are shown in Table 2.

Table 2: Different material background surfaces
Material
Visible
Stainless steel plate
Yes
Plexiglass plate
Yes
Makrolon (polycarbonate)
Yes
Pharma Terrazzo
Yes
Hypalon (glove material)
Yes

Distance from UV source: A stainless steel surface was cleaned with a high grade pre-impregnated IPA wipe as per the process above. The surface was then ‘contaminated’ with a small amount of the 50µm particle suspension. The UV Torch was then set at varying distances from the plate and the plate examined for the visibility of the contamination. The equipment used for this experiment can be seen in Figure 3. The results are shown in Table 3.

Table 3: Distance from source
Distance (cm)
Visible
10
Yes (very good)
20
Yes (good)
30
Yes (good)
50
Yes (moderate)
100
No

Fluorescence of different materials: Small samples of different materials were fixed between two microscope slides. Each sample was examined with the UV Torch and the results recorded. The results for different materials are shown in Table 4.

Table 4: - Fluorescence of different materials
Material
Visible
Rubber bungs
No
White plastic packaging
Yes
Transparent plastic sheet (PVC)
No
Cardboard
Yes
Syringe packaging pouch (plastic and paper)
No
Filter gasket
No
Elastic band from face mask
No
Standard facemask (cleanroom standard)
Yes
Sterile clothing (single use)
Yes
The zip from sterile clothing
Yes
Multi-use sterile garments (sewn)
Yes
Sterile mop cap
Yes
Cleanroom goggles (plastic)
No
Cleanroom grade socks
Yes
Sterile cleanroom wipes
Yes
Sterile cleanroom paper
Yes
Filter material
Yes
PTFE sealing ring
No
Autoclave band
Yes
Single use sterile head cover
Yes
Single use pipette tip (plastic)
Yes

Training

Two groups of 10 trained cleaning operatives and 10 untrained operatives were assigned the task of cleaning a ‘dummy’ RABS (restricted access barrier system), as shown in Figure 5, with pre-impregnated IPA wipes. The RABS was marked with 12 areas of contamination, which were detectable with the UV Torch. Each operative in turn cleaned the RABS.

Table 5: Cleaning effectiveness of trained and untrained operatives

Table 6: Cleaning effectiveness of untrained operatives before and after training

Following each cleaning, the RABS was examined for confirmation of the effectiveness of the cleaning. The results are shown in Table 5. The untrained operatives were then trained and repeated the exercise. The results are shown in Table 6.

In terms of visibly detectable particle size, the 50µm particles were clearly visible on the slide and can be said to be the lower limit of detection.

Figure 5: Dummy RABS

In conclusion, the Klercide UV Validation Torch is an innovation that allows users to observe surface contamination that they might otherwise miss, with the opportunity to make instant process corrections.

The results show that under normal operating conditions, the torch will highlight contamination by a variety of types on all surfaces. In addition to showing the parameters within which the torch will operate effectively, the tests also highlight the significant role that the torch can play in operator training and confirmation of training effectiveness.

This report was presented at the 19th Pharmig Annual Conference held in Nottingham on 16–17 November this year.

Acknowledgement

With thanks to Facility Monitoring Systems for the provision of latex particles.

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