Are our cleanroom suits truly sterile if the soles and insoles of our protective shoes still carry millions of microorganisms? This is a major “blind spot” in current medical infection control practices.

Conventional mechanical washing and drying methods are completely ineffective against drug-resistant bacteria or stubborn mold spores. This deficiency creates a serious risk of cross-contamination in Class 100 or Class 10,000 sterile areas.

This article will provide a standard medical disinfection procedure for protective shoes and introduce modern technological solutions to optimize biosafety. Researchers and bioengineers will find essential technical standards here to upgrade their labs.

1. Sterility Standards and the Risk of Cross-Contamination from Protective Footwear

1.1 Concept of Cleanroom Sterility and Cleanliness Classification

The sterility standards for protective clothing in Vietnam are currently strictly regulated according to the national standard TCVN 8664-1:2011 (completely equivalent to the international standard ISO 14644-1:1999). This document clearly defines the boundaries regarding the density of particulate matter and microorganisms in the space.
For hospital operating rooms or Class 100 (ISO 5) microbiological cleanrooms, the limit for particulate matter with a size of >= 0.5 mu must not exceed 3,520 particles/m³. Meanwhile, a Class 10,000 (ISO 7) environment allows a maximum of 352,000 particles/m³. All equipment, including footwear, entering these areas must undergo a pre-treatment process to achieve the corresponding level of sterility, ensuring that the nominal particle structure is not disturbed.

1.2 Mechanism of Bacterial Dispersal from Protective Shoes into the Air

When we move around in the lab, the mechanical pressure from our feet continuously impacts the floor. This pressure creates a reactive aerodynamic flow at the contact area, inadvertently pushing microorganisms and dust particles adhering to the shoe soles back into the air.
Notably, the inside of the shoe is an ideal environment for dangerous bacterial strains such as Aspergillus spp. or drug-resistant bacteria to thrive due to the moisture from sweat. According to an experimental study published in the US National Library of Medicine PubMed, conventional washing and drying methods with soap only remove surface physical stains. This traditional solution is completely ineffective against heat-resistant fungal spores, keeping the risk of cross-contamination at an alarming level.
(See also: Controlling the repeatability of RSD in fiber analysis to standardize quality standards in the laboratory).

2. Five-Step Disinfection Process for Medical-Grade Protective Shoes

2.1 Details of the Operations in the Transfer Room

To ensure biosafety, technicians are required to operate the process in a closed 5-step sequence in the transfer buffer area:
Collection and Sorting: Gather all soiled shoes after each shift into specialized containers labeled with biological hazard warnings.
Metic Rough Cleaning: Use sterile towels or a vacuum cleaner to completely remove physical dirt adhering to the surface and crevices of the soles.
Deep Disinfection: Arrange shoes in a high-tech radiation device to destroy the cellular structure of microorganisms.
Circulating Drying: Activate the hot air drying mode with controlled temperature to eliminate residual moisture inside the shoes.
Sterile Storage: Transfer shoes to a positive pressure clean cabinet to maintain their sterile condition before starting a new shift.

Throughout the process, operators must wear standard personal protective equipment (PPE) to prevent reverse contamination of equipment from the body.

2.2 Regulations on the Frequency of Infection Control

The frequency of this control procedure depends entirely on the level of biological risk of each specific area. In hospital operating rooms, disinfection must be carried out immediately after each surgery to eliminate pathogens.

For pharmaceutical manufacturing plants and biotechnology laboratories, the processing cycle is usually fixed daily or after each shift. Strict adherence to this frequency helps maintain a continuous sterile state for the entire system.

(Read more: Application of digital microscopes for laboratory data storage to modernize experimental information storage).

Regularly covering and disinfecting protective footwear helps ensure cleanliness in environments requiring sterility

3. Dual Sterilization Mechanism Using UV-C and Ozone Technology

3.1 The Destructive Effect of UV-C on Microbial DNA

The core technology of modern sterilization systems is based on the physical effect of UV-C radiation at the optimal wavelength of 254 nm. This high-energy radiation can easily penetrate the lipid membrane and cell wall of microorganisms.
Once inside the nucleus, UV-C breaks hydrogen bonds and stimulates the creation of thymine dimers on the molecular chain. This process completely paralyzes the ability of bacteria and viruses to replicate and duplicate their DNA/RNA. According to experimental data from research published on ScienceDirect, continuous irradiation for 15 to 20 minutes successfully destroys 99.9% of the genetic structure of harmful bacterial strains.

3.2 The Comprehensive Sterilization Penetration Capability of Ozone

Although powerful, ultraviolet rays have a physical drawback: they only travel in a straight line and create physical dark areas in places that are obscured. To overcome this weakness, dual-action sterilization technology incorporates a stream of ozone (O3) gas with extremely strong oxidizing activity.
Ozone gas will automatically disperse and penetrate deep into the toe, heel, and every stitch of the woven fabric, where UV light cannot reach. This synergistic combination not only destroys the cell membranes of stubborn molds such as E. coli or Salmonella, but also breaks down odor-causing organic compounds, restoring the protective equipment to a completely sterile state.

4. The Impact of UV-C Radiation on Leather and Rubber Materials

4.1 Polymer Aging Mechanism Under High-Intensity Radiation

One of the major concerns of lab managers is the durability of materials when continuously exposed to ultraviolet radiation. Under prolonged exposure to high-concentration UV-C radiation, the polymer structure of vulcanized rubber or artificial leather (PU, Simili) will undergo photoaging (polymer degradation).

The linear chemical bonds break, releasing free radicals that degrade the material’s mechanical properties. This manifests as the leather surface peeling easily, the rubber sole becoming brittle and losing its natural elasticity, and the protective shoes losing their original shape.

4.2 Optimal Sterilization Drying Cycle Solution

To achieve a perfect balance between sterilization efficiency and material lifespan, we must strictly adhere to the manufacturer’s technical recommendations. Absolutely do not keep UV-C lamps running continuously 24/7 in the protective shoe storage chamber.

We should only set the irradiation cycle to a sufficient duration of 15 to 30 minutes per batch to achieve the standard sterilization threshold. At the same time, units should prioritize equipping themselves with shoes made of new generation EVA plastic or high-quality surface-treated genuine leather to optimize long-term UV resistance.
Click the link below to receive a free set of documents on building ISO-standard cleanrooms and in-depth sterile protective clothing management procedures from the Duc Duong expert team:
Register to receive the sterile cleanroom technical documents here

5. Sun-Kyung SK-71020U Commercial Shoe Sterilization and Drying Cabinet Solution

5.1 Technical Specifications and Operating Mechanism of Sun-Kyung

To realize a medical-grade process, the Korean SK-71020U UV sterilization and drying cabinet for shoes, officially distributed by Duc Duong, is an optimal hardware solution. This device features a drying chamber system made entirely of high-grade stainless steel, capable of processing multiple pairs of shoes simultaneously.

Sunkyung’s UV sterilization cabinet for safety shoes helps you achieve maximum sterilization efficiency

This product is imported directly from the globally renowned brand Sun-Kyung. You can find more information about the company’s technological capabilities and international certifications on the Sun-Kyung International website. Thanks to its convection-based hot air circulation drying mechanism, the drying cabinet quickly eliminates accumulated sweat within a safe temperature range, preserving the physical durability of protective equipment.

Technical Specifications	Model: Sun-Kyung SK-71020U
Sterilization Technology	UV-C ultraviolet rays combined with Ozone (O3) gas
Optimal Wavelength	254 nm
Drying Mechanism	Circulating hot air with temperature control
Construction Materials	High-grade stainless steel, UV-resistant tempered glass

5.2 International Standard Active Physical Safety Features

The safety of technicians is always a top priority in the mechanical design of the SK-71020U series. The cabinet door is equipped with a special tempered glass layer capable of absorbing and completely preventing UV-C radiation from leaking into the surrounding lab space.

In particular, the integrated intelligent sensor relay automatically cuts off the power supply to the ultraviolet lamp and ozone generator as soon as the user opens the cabinet door. This active cutoff mechanism completely eliminates the risk of exposure to harmful UV rays that can damage the eyes and skin of operators during work.

6. Comparison of UV-C Sterilization Cabinets and Traditional Methods

6.1 Performance Comparison Matrix Between Protective Equipment Treatment Solutions

To understand why investing in a specialized system is necessary, let’s analyze the performance comparison matrix between currently popular treatment solutions:

Evaluation Criteria	Manual Chemical Spraying	High-Temperature Drying and Washing	Sun-Kyung UV-C & Ozone Cabinet
Shoe Insole Sterilization	Poor (Does not penetrate)	Average (Does not kill spores)	Excellent (99.9% thanks to Ozone)
Material Wear and Tear	High (Chemical corrosive to leather)	Very High (Heat and humidity cause glue to peel)	Low (Inhalation of chemical vapors)
Operational Safety	Low (Inhalation of chemical vapors)	Medium (Risk of thermal burns)	Absolute (Automatic shut-off sensor)
Inspection Records	Unable to prove compliance	Difficult to achieve cleanroom compliance	Full IQ/OQ/PQ certification

6.2 Superior Advantages of Officially Imported Equipment Compared to Locally Manufactured Cabinets

A common mistake made by many facilities is choosing cheap, domestically manufactured cabinets to save on initial costs. However, these self-made devices often use substandard UV lamp components of unknown origin, leading to emission wavelengths that do not meet theoretical standards.
Conversely, the genuine Sun-Kyung machines distributed by Duc Duong undergo rigorous microbiological testing procedures. The products possess full practical testing certificates from independent international organizations, giving businesses complete peace of mind when facing strict quality inspections by the Ministry of Health.

7. Periodic Calibration Procedure for Sterilization Drying Equipment

7.1 Method for Measuring Actual UV-C Radiation Intensity

In cleanroom management, we cannot assess equipment quality intuitively. Ultraviolet (UV) lamps, after a period of continuous operation (usually exceeding 8,000 hours), will experience natural light degradation.

At this point, although the lamp may still be visible to the naked eye emitting its characteristic blue light, the actual germicidal wavelength is no longer within the optimal range. Technicians must periodically use a specialized UV radiometer to accurately determine when to replace the lamp.

7.2 Preparing IQ, OQ, and PQ documentation for competency assessments

For a sterile drying system to be accredited in pharmaceutical factories or hospitals, preparing legal documentation is mandatory. The standard calibration documentation must include all three core components: Installation documentation (IQ), Operational documentation (OQ), and Actual performance documentation (PQ).

These documents are scientific evidence proving that the equipment consistently operates stably and achieves the sterilization performance as designed. Careful record keeping of calibrations helps the unit easily pass GMP certification audits or international laboratory competency standards.

Conclusion

Comprehensive sterilization control for safety shoes using dual UV-C and Ozone sterilization technology is a prerequisite for protecting the cleanliness of modern laboratory and hospital environments.
Investing in a standardized, integrated solution like the Sun-Kyung SK-71020U sterilization drying cabinet not only minimizes the risk of biological cross-contamination and protects employee health, but also ensures your facility always meets the most stringent inspection standards.

Contact Duc Duong today to have our professional engineering team survey and advise on the optimal sterilization drying system design and receive the best official price quote.

 

DUC DUONG SCIENCE AND TECHNOLOGY COMPANY

Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa Ward, Binh Tan District, Ho Chi Minh City

Tel: (028) 3762 8042 – 3762 8043 – 3750 8514 – 3750 8793

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Email: ducduong@ducduongco.com

Website: ducduongco.com

ZALO OA: DUC DUONG SCI

 

FAQ – Frequently Asked Questions about cleanroom shoe sterilization

1. Does ozone gas from the shoe sterilization cabinet harm the health of employees?

Answer: High concentrations of ozone gas can irritate the human respiratory system. However, genuine imported Sun-Kyung equipment is designed to operate in a completely closed cycle. The automatic system integrates a filter that decomposes excess ozone into oxygen before the drying cycle ends, ensuring absolute safety when technicians open the cabinet door to retrieve items.

2. Can 70% alcohol be used as a substitute for UV sterilization cabinets?

Answer: It cannot be a complete replacement. 70% alcohol only has an immediate sterilizing effect on flat, smooth surfaces and evaporates very quickly in the air. This manual method is completely ineffective against the porous structure inside the shoe or mold spores hidden deep in the toe area of ​​cleanroom protective shoes.

3. How do I know if the UV-C lamp in my shoe dryer has reached the end of its sterilization lifespan?

Answer: We must use a UV radiation test card or a digital photoelectric intensity meter every 6 months. When the lamp’s output power drops below 70% of its original specifications, the lamp must be replaced immediately, even if the internal filament is still glowing green.

4. How much electricity does the Sun-Kyung SK-71020U shoe sterilization dryer consume per drying cycle?

Answer: The device uses an intelligent heating system controlled by a new generation microprocessor combined with an optimized low-power UV-C lamp system. Thanks to this, the total electricity consumption for an operating cycle is extremely economical, perfectly meeting the continuous 24/7 operation frequency of large-scale hospitals and factories.

5. Can the soft rubber material of Cleanroom Clogs be used in a UV drying oven?

Answer: Absolutely. Specialized cleanroom clogs made from high-grade polyurethane or antistatic rubber have excellent UV radiation resistance. Users only need to remember to set the drying cycle at a low to medium temperature range from 40°C to 50°C for perfect sterilization without denaturing or shrinking the material.