In food manufacturing facilities, buffer zones connecting clean and non-clean areas, including air showers and pass boxes, act as vital barriers against cross-contamination and help sustain stable clean environments. These spaces differ from high-grade core production zones and ordinary non-clean areas alike. For this reason, targeted and differentiated disinfection measures are required. Such arrangements can secure satisfactory disinfection results while striking a balance between operational efficiency and safety. This article mainly discusses how to set chlorine dioxide disinfection frequencies and operational methods for these buffer zones, matching the hygiene standards of adjacent areas.

1. Differences Between Adjacent Zones: Baseline Disinfection Specifications for Clean and Non-Clean Areas

1. Clean areas cover key production processes such as batching, filling and inner packaging, where strict microbial control is mandatory. In these areas, chlorine dioxide is often applied through regular space fumigation or atomization after each shift or daily production, paired with surface wiping for equipment. The disinfectant concentration is controlled within a safe and effective low range (50–80 ppm), so residues will not adversely affect products and the surrounding environment.
2. Non-clean areas involve raw material warehouses, outer packaging sections, changing rooms and other regions with lower microbial risks. Disinfection work focuses on routine preventive treatment after daily cleaning. Chlorine dioxide can be sprayed or used for floor mopping 1 to 2 times every week at a slightly higher concentration (80–100 ppm), with sufficient ventilation and proper protection for on-site staff.

2. Special Attributes of Buffer Zones: Functional Barriers and Potential Contamination Risks

Air showers and pass boxes are essential passages for staff and materials entering clean areas. Dust and microorganisms easily accumulate on inner surfaces, filter outlets, interlocking doors, transfer racks and other components. If facilities simply adopt disinfection standards for either clean or non-clean areas, two problems may emerge. Insufficient disinfection will turn these passages into contamination transmission channels; over-disinfection will lead to wasted materials, equipment corrosion and threats to personnel health.

Therefore, disinfection management for buffer zones should follow the principle of independent assessment and dynamic adjustment. The core idea is to adopt the stricter control standard from the connected areas, and strengthen disinfection for high-risk spots unique to buffer zones.

3. Establish Differentiated Disinfection Frequencies Based on Usage Volume and Risk Level

3.1 Air Shower

• Frequent surface disinfection: Frequently touched surfaces inside, including door handles, inner walls and fan control buttons, shall be wiped with low-concentration chlorine dioxide solution (50–80 ppm) every 2–4 hours, consistent with the disinfection frequency for high-contact points in clean zones.
• Daily deep disinfection: At the end of each production day, carry out spray disinfection inside the air shower. Keep the disinfectant in contact for 10–15 minutes before ventilation. The frequency is higher than standard disinfection for regular non-clean areas.
• Periodic fumigation: Coordinate with the fumigation schedule of clean areas, and conduct closed gaseous fumigation once every one or two weeks. This helps remove microorganisms in filter downstream areas and hard-to-clean dead corners.

3.2 Pass Box

• Disinfection after each transfer: After every batch of material transfer, wipe or spray chlorine dioxide on inner wall panels and support racks on both sides of the pass box. This follows the real-time disinfection principle applied to equipment within clean areas.
• Full disinfection at the end of each shift: The frequency is higher than requirements for non-clean areas. Complete internal and external treatment shall be carried out after each shift, combining UV interlock disinfection (if equipped) and chemical disinfection.
• Monthly targeted disinfection inspection: Carry out dedicated cleaning and disinfection on sealing strips, interlock devices and other subtle parts to prevent microbial buildup.

4. Reasonable Selection of Disinfection Methods Matching Zone Structure and Materials

1. Combine spraying and wiping: Use fine mist chlorine dioxide for complicated structures inside air showers such as nozzles and plenum grilles to achieve full coverage. Wiping is preferred for smooth inner surfaces of pass boxes to avoid aerosols drifting into clean areas. All disinfectant solutions need accurate preparation, and compatibility tests shall be completed to check corrosion risks to stainless steel, plastic and other common materials.
2. Unified arrangement for gaseous fumigation: When fumigation is arranged for clean areas, connected buffer zones must be included in the overall plan, ensuring chlorine dioxide gas can reach all connected spaces. Sealing work should be done for doors linking to non-clean areas, or fumigation can be arranged during off-production hours to prevent gas leakage.
3. Dynamic monitoring and scheme adjustment: Set sampling points for settle plate bacteria and airborne bacteria in buffer zones, and adjust disinfection frequency according to monitoring trends. If test results continuously exceed limits, increase disinfection intensity. If long-term qualified data is obtained, extend treatment intervals appropriately after verification, so sanitation management can be guided by actual monitoring data.

5. Auxiliary Control Measures Centered on Personnel and Material Flow

1. Bidirectional differentiated control: Disinfection standards for the passage from non-clean area to clean area shall be stricter than the reverse direction. For example, outer door frames and handles of pass boxes require more frequent disinfection than inner ones.
2. Separate disinfection records: Buffer zones shall use independent record forms, separated from documents for clean and non-clean areas. Records should clearly mark inspection locations, disinfectant concentration, contact time and operators, facilitating traceability and audit work.
3. Focused staff training: Training should highlight the special hygiene status of buffer zones. Operators need to master different entry rules and disinfection responsibilities for various zones to avoid cross-contamination caused by improper operation

No single link can operate separately within the food production hygiene system. Disinfection management for buffer zones reflects a company’s hygiene awareness based on risk analysis and refined control. By formulating matched chlorine dioxide disinfection schemes for areas with different hygiene requirements and focusing on variable risk points inside buffer zones, enterprises can build a solid hygiene barrier between clean and non-clean regions. Optimized management can also improve the utilization efficiency of disinfection supplies, guarantee food safety and drive continuous quality improvement.