Title: Validation and application of the personnel factor for the garment used in cleanrooms (1).
Author: Mike Guiry
A cleanroom is a box (sterile cleanroom) where sterile products are made for injection into the blood stream; therefore it is critical that there is no contamination. There are many ways of contaminating the sterile cleanroom, product, equipment, air, cleaning, and the design and set up of the room but the personnel working in the sterile room are the largest source of contamination. Personnel spend over 85% of their working day in the cleanroom. Personnel shed many particles throughout each working day. When motionless they shed 100,000/minute, walking slowly 5,000,000/minute, 7,500,000/minute walking briskly and walking fast 10,000,000/minute walking fast. Clean room garments are worn to protect the product from these particles. The aim of this study is to measure the effectiveness of the cleanroom garments and fabrics and to quantify particle penetration and shedding. Furthermore the life-span of a washed but non pre sterilised cleanroom woven garment was investigated in respect to particle penetration.
Review of the article in relation to their work and findings.3 methods were used to evaluate these studies. (2)
Particle penetration test
2.Particle shedding test -Helmke drum tumble test
3.Dispersal chamber test
1.Particle penetration test
In an ISO 4 cleanroom with the Average Airflow Velocity of 0.254 – 0.457 m/s and the air changes rate of 300 – 540 per hour, a filter container was fitted with a vacuum pump assembled to utilize this air stream through the garment. (3) The particles in the air were counted before and after going through the garment which had a pressure drop i.e. 4.5mm H2O. The penetration of particles was determined by measuring the upward and downward flow of particles.
2.Particle shedding test – Helmke drum tumble test
The helmke drum test (4) is widely used to assess the efficiency of the cleaning process as it measures particles released from dry garments. A body box was utilised to mimic the cleanroom contamination and the particle filtration of the conditions were assessed. This is a realistic method as it breaks the static charge. The apparatus was set up in an ISO 4 cleanroom with the Average Airflow Velocity of 0.254 – 0.457 m/s and the air changes rate of 300 – 540 per hour cleanroom and laundered but non pre- used sterilisation garments were employed in the experiment. The air was pulled from the inside of the rotating drum through sampling tube from the airborne particle monitor and a particle counter was used to determine the number of airborne particles. Therefore a measure of the particles generated by the garments was obtained.
3.Dispersal Chamber Test
An intentionally designed room fitted with High Efficiency Particle Air (HEPA) Filters was constructed in an ISO 4 cleanroom. The vertical uni-direction air speed was at 0.35mls. An operator was positioned in this room and the number of particles generated were counted using a particle counter. The test operator performed a sequence of movements from motionless to walking and arm and leg movements. A mathematical equation was used to determine the level of airborne contaminants after each movement.
Conclusion.Three main theories were established as a result of these studies:
Particle penetration increased with increased HVAC face velocity and decreased particle size below 1?m.
The more movement the operator performed the more particles were shed.
The laundered garments allowed larger and more particles to penetrate in correlation with the wear of the garment. It was recommended that an upper particle size limit of 5?m be applied.
In conclusion I agree with the findings of these studies however further studies should be carried out to determine the most effective and efficient airflow patterns which will result in the least particle shedding. Different garment fabrics, synthetic material, nylon, ceramic terylene or polyester should be considered. Cleanroom set-up and design should be assessed to minimize operator movement and thus decrease particle shedding. Laundered garments were used in these experiments perhaps it would be more beneficial to conduct the experiments using sterile garments.
Even though this study did not investigate all scenarios, it is a valuable asset in the continuing evaluation of the effect of cleanroom operator activity and the life span of garments on the sterility status of the cleanroom environment. We must again emphasize that cleanroom garments are designed to protect the product from the human.
References.Hu S, Shiue A. Validation and application of the personnel factor for the garment used in cleanrooms. Building and Environment. 2016;97:88-95.
Institute of Environmental Sciences and Technology (IEST), IEST-RP- CC003.3:
Garment System Considerations for Cleanrooms and Other Controlled Environments,
Z. Vokac, V. Køpke, P. Keul, Assessment and analysis of the bellows ventilation
of clothing, Text. Res. J. 43 (1973) 474e482. Institute of Environmental Sciences and Technology, Arlington Heights, IL, 2003.G.A. Helmke, Tumble test for determining the level of detachable particles associated with clean room garments and clean room wipers, in: Proceedings
of the 28th Annual Technical Meeting of the Institute of Environmental Sciences,
Institute of Environmental Sciences (and Technology), Mt. Prospect, IL, 1982.