How to disinfect xenon light transfer Windows correctly?

When disinfecting xenon light transfer Windows, it is necessary to combine their structural characteristics with the disinfection standards of clean areas. A complete system should be formed from pre-disinfection preparations, selection of disinfection methods, and operation procedures to effect verification to ensure thorough disinfection without affecting the performance of the equipment. The following is the detailed operation guide:
I. Preparations before disinfection
Cleaning and pretreatment
Use a lint-free cloth dipped in 75% ethanol or neutral detergent to wipe the inner walls of the transfer window, trays, door handles, and observation Windows, removing surface dust, stains, and microbial carriers (such as fibers and debris) to avoid contaminants affecting the disinfection effect.
If materials that are prone to residue (such as powder or liquid) are passed, they should first be wiped repeatedly with a moist lint-free cloth and then dried with a dry cloth to ensure that there are no visible contaminants on the surface.
Equipment status check
Confirm that the interlocking function of both sides of the door is normal (to prevent the leakage or contamination of the disinfectant when the door is opened during disinfection), there is no obvious dust accumulation on the surface of the xenon lamp tube (if there is dust accumulation, wipe it with ethanol first), and the fan is operating normally (to ensure effective air circulation during disinfection).
Ii. Core Disinfection Methods and Operating Procedures
(1) Xenon ultraviolet disinfection (Conventional disinfection)
Principle: The ultraviolet light emitted by xenon lamps (with a main wavelength of 253.7nm) can destroy the DNA/RNA structure of microorganisms, causing them to lose their reproductive ability. It is suitable for surface and air disinfection.
Operation steps
Item placement: Put the items to be disinfected into the transfer window, arrange them evenly to avoid overlapping (ensuring sufficient ultraviolet radiation), close the doors on both sides, and confirm interlocking.
Parameter Settings: Set the disinfection time according to the equipment manual (usually 30-60 minutes), and the power of the xenon lamp needs to meet the design standard (such as power ≥10W per cubic meter of space).
Start disinfection: Turn on the xenon lamp, keep personnel away from the transfer window (ultraviolet rays can damage the eyes and skin), and do not open the door during the disinfection process.
After the disinfection is completed, wait for 5 to 10 minutes (to allow the residual ozone to decompose. If no ozone is produced by the equipment, there is no need to wait) before opening the door to retrieve the items.
Precautions
Ultraviolet rays have weak penetrating power, so items should be placed exposed. The packaging materials should be made of materials that ultraviolet rays can penetrate (such as transparent plastic, avoiding aluminum foil and opaque paper boxes).
If there are shaded areas (such as corners) in the transfer window, you can rotate the items regularly or install a rotating tray inside to ensure even illumination.
(2) Chemical Disinfection (Enhanced Disinfection/Periodic Disinfection)
Applicable scenarios: When high-risk items (such as biological samples, and laboratory equipment) are transferred, the risk of equipment contamination is relatively high, or the effect of xenon light disinfection is insufficient, chemical disinfection should be combined.
Common disinfectants and operations
Disinfectant type, concentration, disinfection method, and precautions
75% ethanol (70%-75%) is flammable when used to wipe the inner walls, pallets, and surfaces of items. When disinfecting, keep away from fire sources. After wiping, it needs to be dried (to avoid residual liquid affecting subsequent ultraviolet disinfection).
Spray or wipe with 3%-6% hydrogen peroxide solution (for 10-15 minutes). Use food-grade or medical-grade products. High concentrations have a slight corrosive effect on metals. After disinfection, wipe with clean water.
Quaternary ammonium salt disinfectants should be diluted as per the instructions and wiped onto the surface (for 5-10 minutes). Do not mix them with anionic cleaners (such as soap), as they are less effective against Gram-negative bacteria.
Ozone (optional) concentration 0.3-0.6ppm is produced by an ozone generator (action time 30 minutes). It should be used in an unattended state. After disinfection, ventilated for 30 minutes (ozone is irritating to the respiratory tract). The equipment must have an ozone generation function.
Operation example: Hydrogen peroxide spray disinfection
Remove all items from the transfer window and pre-clean the surface with 75% ethanol.
Fill the 3% hydrogen peroxide solution into a sprayer and evenly spray the inner walls, top, bottom, and tray to ensure the surface is moist (the spray volume is approximately 5-10 mL /m³).
Close the doors and Windows, let it stand for 10 to 15 minutes. After the disinfectant takes effect, turn on the fan and run it for 15 minutes to expel the residual gas.
Iii. Disinfection Treatment in Special Scenarios
Emergency disinfection for biological contamination
If biological sample leakage (such as culture medium or blood) occurs within the transfer window, the following steps should be followed for handling:
Immediately close the doors and Windows to prevent the spread of pollutants. Cover the leaked substance with absorbent paper and then spray it with a disinfectant solution containing 1000-2000mg/L of available chlorine (such as sodium hypochlorite) for 30 minutes.
Carefully remove the absorbent paper and contaminants, put it in a special garbage bag, and seal it. Wipe the leakage area and a 50-cm radius around it with 75% ethanol. Repeat this twice.
Turn on the xenon lamp for disinfection for 60 minutes, while running the fan to maintain air circulation. Finally, use a dust particle counter to test the cleanliness after disinfection.
Disinfection of items after transfer
For items that are not resistant to ultraviolet rays (such as culture media and light-blocking medicines), chemical disinfection can be carried out first (such as wiping the outer packaging with ethanol), then they can be placed in the transfer window and the fan can be turned on to run for 10 minutes (to reduce the adhesion of surface dust through air filtration). There is no need to turn on the xenon lamp (to avoid damage to the items caused by light).
Iv. Verification and Record-keeping of disinfection effects
Physical index monitoring
Measure the irradiation intensity of the xenon lamp with a UV radiometer every month (it should be ≥100μW/cm² at a distance of 10cm from the lamp tube). If it is lower than 80μW/cm², the lamp tube needs to be replaced (see the previous section "Maintenance of Xenon Lamp Tube").
Every quarter, wipe the inner surface of the transfer window (such as corners and door handles) with an ATP fluorescence detector to test the ATP value (standard value ≤10RLU; if > 30RLU, re-disinfection is required).
Microbial monitoring
Microbial sampling should be conducted every six months: Press the inner wall of the transfer window, trays, and other parts with contact plates (TSA medium), and count the number of colonies after 48-72 hours of culture (standard: ≤5CFU/plate). If the standard exceeds the limit, the source of contamination (such as filter leakage, or disinfection process defects) needs to be analyzed.
Record Management
Establish a "Transfer Window Disinfection Record Form", detailing the disinfection date, method, disinfectant name and concentration, action time, and operator, as well as the effect monitoring results (such as ultraviolet intensity, ATP value, colony count), to facilitate traceability and quality auditing.
V. Taboos and Safety Points of Disinfection Operations
Prohibited behavior
When disinfecting, use highly corrosive disinfectants (such as concentrated hydrochloric acid or nitric acid) to avoid damaging the surface of stainless steel or the sealing rubber strips.
Disinfect the uncleaned transfer window directly (contaminants will form biofilms, reducing the effectiveness of the disinfectant).
When there are obvious stains on the surface of the xenon lamp tube, turn on the disinfection (the stains block ultraviolet rays, causing local disinfection to fail).
Safety protection
When handling chemical disinfectants, wear dust-free gloves and goggles. If the disinfectant splashes onto the skin or eyes, rinse immediately with plenty of water for 15 minutes and seek medical attention.
When xenon light disinfection is carried out, it is strictly forbidden to look directly at the lamp tube (ultraviolet rays can cause corneal damage), and the equipment must be labeled with an "Ultraviolet Hazard" warning sign.
Vi. Scientific Setting of Disinfection Cycles
Daily disinfection: After each item transfer, turn on the xenon lamp for disinfection for 30 minutes (or follow the device's set program).
Enhanced disinfection: Conduct chemical disinfection once a week (such as combined disinfection with ethanol and hydrogen peroxide), and carry out surface disinfection of the air intake surface of the filter once a month (wipe the outer frame of the primary filter with ethanol).
Periodic verification: Every year, a third party is entrusted to confirm the disinfection effect (such as the biological indicator challenge test, using Bacillus subtilis spore strips, with a sterilization rate of ≥99.9%).
Summary
The disinfection of xenon light transfer Windows should adopt a combined strategy of "ultraviolet physical disinfection as the main and chemical disinfection as the auxiliary", and the disinfection plan should be dynamically adjusted according to the risk level of the items and the frequency of use. The key lies in thorough cleaning before disinfection, parameter control during disinfection (such as ultraviolet time and disinfectant concentration), and effect verification after disinfection. At the same time, it is necessary to strictly follow the disinfection norms of the clean area to avoid introducing secondary pollution due to improper operation. For high-risk scenarios (such as biological laboratories and GMP workshops), it is recommended to incorporate the disinfection process into the SOP and provide regular training for operators to ensure the reliability and repeatability of the disinfection effect.