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The core functions and detailed differences between air shower and pass box in cleanrooms:

The core commonality of both is to control contamination and maintain the cleanroom environment level. Both must comply with regulations and standards such as GMP and ISO 14644. However, there are significant differences in their applicable objects, working principles, and operating requirements, as detailed below:

 I. Similarities 

1. Structural Anti-Cross-Contamination

Both are equipped with a double-door interlocking device, preventing both doors from opening simultaneously. This physically blocks the direct airflow between the cleanroom and non-cleanroom (or different levels of cleanrooms), preventing cleanroom pressure imbalance and pollutant diffusion.

2. Consistent Regulations and Management Requirements

Both must be included in the cleanroom equipment management system, with complete maintenance and calibration records, and subject to regular audits and inspections.Daily cleaning requires the use of lint-free cleanroom wipes to wipe the inner walls, and no miscellaneous items are allowed to be stored inside the equipment to prevent them from becoming new sources of contamination.

3. Similar Maintenance and Calibration Principles

Both require regular inspection of the door seal integrity and the operating status of functional components, and timely replacement of aging consumables (such as filters and UV lamps) to ensure that the equipment is always in a compliant operating state.

 II. Differences 

1. Applicable Objects

Air shower are applicable to personnel and large material carriers, such as operators and inspectors entering the cleanroom, as well as stainless steel trolleys and large turnover boxes carrying materials. They can meet the needs of large and bulk material carriers.

Pass box are only suitable for small materials, tools, and documents, such as sample bottles, reagent tubes, cleanroom wipes, sterile gloves, and clean versions of batch production records. Personnel or large items are strictly prohibited from passing through.

2. Core Purification Principles

The air shower chamber uses high-speed airflow blowing and filtration as its core principle.A fan blows air, filtered by a high-efficiency particulate air (HEPA) filter, through nozzles at a speed of no less than 25 m/s, forcibly removing dust particles and microorganisms attached to personnel clothing fibers and trolley surfaces. The blown-off contaminants are collected through the return air vents and filtered again, forming a circulating purification process.

The pass box uses physical isolation and auxiliary disinfection as its core principle. The basic model only achieves spatial isolation through interlocking doors and has no active purification function; models with UV disinfection have a built-in 253.7nm wavelength UV lamp, which, when activated, irradiates for 15-30 minutes, killing bacteria by destroying the DNA structure of microorganisms.There is no airflow blowing function throughout the process, so it does not change the attachment state of particles on the surface of objects.

3. Installation Location and Environmental Requirements

The air shower chamber should be installed in the buffer zone at the main entrance for personnel/materials in the clean area, forming a three-level separation between the non-clean area and the clean area (non-clean area → air shower chamber → clean area). The installation area needs to have sufficient space for passage to ensure that the doors can be fully opened. It also needs to be linked to the pressure difference of the clean area; the pressure difference inside the air shower chamber should be slightly lower than the clean area and higher than the non-clean area.

The pass box is directly embedded in the partition wall between the clean area and the non-clean area, or between different levels of clean areas. The installation location should be convenient for personnel on both sides to operate. The wall opening size needs to match the specifications of the pass box. No additional pressure difference control is required; it only needs to ensure consistency with the environmental parameters of the surrounding area.

4. Operating Procedure

The operating procedure of the air shower chamber is as follows: After personnel or a trolley enters, the outer door closes, and the interlocking device locks the inner door; the infrared sensor triggers the fan to blow air, with a preset blowing time of 15-30 seconds (adjustable according to the cleanroom class); after the blowing is completed, the fan stops, the inner door unlocks, and personnel or the trolley can enter the clean area. Forcibly opening the interlocking doors is prohibited throughout the process. The emergency stop button should only be used in emergency situations. The pass box operates as follows: personnel on the non-clean side open the outer door, place the items inside, and close the outer door to ensure the interlock is activated; if it is a model with UV disinfection, the UV lamp must be turned on and remain on for the set disinfection time before being turned off; personnel on the clean side confirm that the outer door is closed, then open the inner door to retrieve the items, and finally close the inner door. Note that it is prohibited to open either door while the UV lamp is on to prevent UV radiation leakage and potential injury.

5. Maintenance and Calibration Details

Daily maintenance of the air shower room includes checking that the fan is running without abnormal noise, the sensing device is sensitive, and the interlock function is working correctly; weekly maintenance includes cleaning the pre-filters, wiping the nozzles, and checking that the door seals are not damaged; monthly maintenance includes checking the integrity of the HEPA filter (PAO leak test) and calibrating the airflow speed to be no less than 25 m/s; every six months, the pre-filters should be replaced and the fan motor should be inspected.

Daily maintenance of the transfer window includes checking that the interlock function is working correctly, the UV lamp indicator light is on (for models with disinfection), and the observation window is free of stains; weekly maintenance includes wiping the internal surfaces with 75% ethanol and checking that the door hinges rotate smoothly; monthly maintenance includes calibrating the UV lamp irradiation intensity (which must reach a bactericidal threshold of ≥70 μW/cm²) and replacing aging seals; quarterly maintenance includes replacing the UV lamp tubes (which typically have a lifespan of 8000 hours).

 III. Complementary Functions 

The air shower room addresses the active purification of personnel and large material carriers, preventing the entry of large amounts of contaminants into the clean area; the transfer window addresses the sterile isolation and transfer of small items, avoiding disruption of the clean area pressure difference and environmental stability due to frequent door openings. Both are indispensable and together constitute a comprehensive pollution control system for personnel and material entry and exit in the clean area.