Chlorine Dioxide Gas Decontamination vs. Liquid Disinfection

The Bausch + Lomb (B&L) Vision Care production facility in Greenville, South Carolina, manufactures contact lens solutions in sterile processing areas within a clean environment. Because the manufactured products either clean contact lenses or are placed directly into a person’s eyes, they must be sterile and containers must be filled and sealed in an extremely high-quality environment.

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Each year, the facility closes for planned maintenance shutdowns. Though necessary, these shutdowns create unsterile environments because foreign equipment, tools, and people enter the clean areas. Therefore, the environment must be cleaned and disinfected before normal production resumes.

Manual Cleaning and Disinfection

Historically, manual cleaning and disinfection procedures to prepare the plant for reopening required nearly 100 personnel working in multiple shifts for over six days (three days to clean and then three days to disinfect rooms using mops and buckets). Rooms were cleaned with detergents and/or surfactants and then wiped down with a high-level disinfectant solution. To maintain high-quality standards, this cleaning and disinfection process has multiple stages: gross cleaning, followed by fine cleaning, followed by at least three rounds of disinfection. If any posttreatment swabs test positive for contaminants, that particular area might require additional treatment.

In general, manual cleaning and disinfecting activities use physical cleaning motions and disinfectants to kill organisms. Once cleaning is complete, a liquid disinfectant is used to disinfect the area. This cleaning process is considered effective at removing biological contaminants on environmental surfaces.

The disinfectant used is typically applied to a surface, a device surface, or a cloth. Once applied, the disinfectant sits for the contact time prescribed by its manufacturer.

The disinfectant used at the facility is a fast-acting, liquid cold sterilant/disinfectant, filtered through a 0.2-micron filter and specifically formulated for use in the sterilization and disinfection of hard environmental surfaces in pharmaceutical, medical device, biotech, and cosmetic manufacturing facilities. This product is a stabilized blend of peracetic acid, hydrogen peroxide, and acetic acid that provides fast, effective control of microbes, including spores. The disinfecting agent is typically used for a number of reasons: (a) ease of use; (b) consistent dilution because no mixing or activation is required; (c) efficacy—microbial control against bacteria, fungi, viruses, and bacterial spores; (d) safety—the low toxicity profile supports worker safety; (e) convenience—excellent material compatibility allows use on most environmental surfaces; and (f) flexibility and versatility of use—depending on the use concentration, contact time, and application method, the product can be used as a sterilant, sporicide, disinfectant, or sanitizer.

This process is costly and labor-intensive. The manufacturing facility consists of filling rooms, sterile staging areas, gowning areas, and sterile hallways, each with a significant amount of surface area. The filling lines and equipment have many surfaces to treat and thus require large amounts of the disinfectant solution. The company would spend approximately $150,000 to fully disinfect the entire sterile processing facility, and the disinfection process would take about three (24-hour) days and require a crew of nearly 100 people.

Gross Cleaning

Gross cleaning consists of scrubbing all stainless steel equipment with a cleaning solution and using brushes to remove all visible residue. Walls and ceilings are mopped, HEPA filters are wiped with an isopropyl alcohol (IPA)–soaked class 100 wipe, all returns are wiped with disinfectant-soaked lint-free towel, and floors are mopped with a disinfectant.

Fine Cleaning

Fine cleaning occurs after gross cleaning and consists of spraying a cleaning solution on all surfaces except HEPA filters and wiping all stainless steel surfaces and equipment, HVAC return vents, waste containers, curtains, plexiglass, and equipment. Some equipment is uninstalled to facilitate better cleaning. Walls and ceilings are mopped with the cleaning solution and floors are mopped with a disinfectant.

Disinfection

Prior to switching to gas decontamination, there were three rounds of disinfection. In the first round, everything was sprayed with a disinfectant solution, curtains and plexiglass were wiped with a disinfectant-soaked lint-free towel, and all walls and floors were mopped. The second round repeated the first round’s cleaning and included wiping the inside of some equipment hoppers as well. In the third round, all surfaces were sprayed and wiped with the disinfectant solution, and then all surfaces were wiped with an IPA-soaked class 100 wipe.

Once the cleaning/disinfection process was complete, the areas were swabbed to confirm the efficacy. If any area tested positive for contaminants, it had to be cleaned and disinfected again, increasing costs and requiring more time and effort.

Given the labor intensiveness, variability, lack of repeatability, and cost of the manual cleaning and disinfection process, B&L sought more efficient, reliable, and cost-effective alternatives. Chlorine dioxide gas was chosen as a test agent because it has been shown effective at decontamination of large-scale facilities,, ,  rooms and suites of rooms,, , , ,   isolators,, ,   processing vessels and tanks,, and biological safety cabinets.,  See Table 1 for a comparison of manual disinfection and decontamination using chlorine dioxide gas.

Table 1: Comparison of manual disinfection and decontamination using chlorine dioxide gas. Manual Disinfection Chlorine
Dioxide
Gas Treatment time 3 days (97 people) 2 days (6
people) Efficacy Some positive swabs All biological
indicators
dead; no
positive
swabs Cost ~$150,000*
(~$100,000 in disinfectant solution +
~$50,000 in labor) $97,000
(all-inclusive) Application method Spray and wipe Gassing Method of kill Oxidation Oxidation Level of kill Sterilant Sterilant

Chlorine Dioxide Decontamination

Because chlorine dioxide is a true gas at room temperature (boiling point -40 °C), its distribution and penetration do not rely on an operator’s skill. As a gas, it reaches all areas—including cracks, crevices, and difficult-to-reach surfaces—and provides full coverage, making decontamination more successful than manual disinfection.

As the FDA states, “suitability, efficacy, and limitations of disinfecting agents and procedures should be assessed.” To do this, biological indicators (BIs) were placed throughout the space to test the process and ensure proper decontamination.

Gas Material and Equipment

• The following equipment was used to decontaminate the space:
• A 330,000 ft3 (9,344 m3) aseptic classified space
• Manual chlorine dioxide gas–generating systems (qty. 14)
• Chlorine gas cylinders (2% chlorine/98% nitrogen) (qty. 28)
• EMS chlorine dioxide gas–monitoring systems (qty. 2)
• Extension cords (100-feet and 25-feet; qty. 10 each)
• Blowers (approximately 1,800 CFM each; qty. 18)
• Small fans (qty. 40)
• Duct tape and plastic
• Spools of ¼-inch red polyethylene tubing (for gas injection; qty. 28)
• Spools of ¼-inch green polyethylene tubing (for gas sampling; qty. 10)
• Rolls of thin 3-mil plastic sheeting (for conveyor sealing; qty. 4)
• Roll of 6-mil plastic sheeting (for large-opening sealing; qty. 1)
• Low-level chlorine dioxide gas safety sensors (qty. 3)
• Pairs of BIs—106 Geobacillus stearothermophilus spore strips (qty. 20)
• Prepared culture media: formulated tryptic soy broth modified with pH indicator (qty. 20)

Sterile Processing Facility Decontamination

Gross and fine cleaning of the facility was completed as previously described prior to the chlorine dioxide gassing team’s arrival. Once cleaning was completed, decontamination followed in the ensuing steps.

Day 1—Arrival and Initial Setup

The decontamination team of five people arrived onsite in the early afternoon. The listed equipment was brought to the decontamination area, and the manual chlorine dioxide gas generators were set up outside the decontamination space. External windows and doors were taped and sealed to contain the gas during the actual decontamination process.

Day 2—Setup

The decontamination team arrived in the morning and split into smaller teams to continue sealing the space and setting up the decontamination equipment. Sealing began in the packaging transition area, which has small openings in walls where conveyors exit with finished product in sealed containers. These openings were sealed with a mixture of plastic and duct tape. Because of the nature of the facility, a special duct tape that leaves little to no residue was used. Sealing was performed on the outside surfaces so the sterilant would not miss important internal surfaces.

The HVAC for some areas was turned off, allowing roof units to be sealed. Some HVAC units were left on for workers’ comfort and to control humidity in the space.

Some HVAC units had exhaust and supply vents common with areas outside the cleanroom space. When gas enters ductwork, it will leak to outside areas unless the vents are sealed. Therefore, common vents outside the space were located and sealed with duct tape and plastic.

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At the same time that the area was being sealed off, another team set up the gas generation system by evenly distributing blowers and small fans throughout the space. Blowers and fans were usually placed close to power outlets. Because the fans were used to speed up the diffusion of the gas and were not needed to force the gas into specific areas, where they were placed was not critical.

Red gas injection tubing was run from each generator to multiple locations within the space. Gas generators were located outside the space, ensuring that generators could easily be stopped if necessary for safety. Some gas injections points were combined in one area to minimize the time to place the tubing.

After the gas injection tubing was placed, the green tubing used for sampling gas concentrations was run from the chlorine dioxide gas–monitoring system’s gas sensor, which was placed outside the decontamination space, to locations in the space away from the gas injection sites. The monitoring system used a small diaphragm pump to draw in air samples from the different locations (one at a time) through a photometer to read the actual real-time chlorine dioxide concentration. The photometer measures the absorbance of the gas, and the monitoring system converts this absorbance into a chlorine dioxide gas concentration reading in mg/L. The monitoring system uses these readings to determine when the concentration reaches the required dosage.

In some projects, some areas may not come up to concentration as expected, either due to leakage or because gas consumption is greater than expected. If that happens, some generator injection points are moved to the spare injection points. Spare gas injection points were not used on this project.

Once the fans and tubing were set up, and most HVACs sealed, 20 pairs of BIs were placed at 20 locations throughout the facility to test the efficacy of the process. Pairs of BIs were used based on validation studies performed by Luftman and colleagues. In this study, it was decided that if both BIs were positive, the results were positive (growth); if both BIs were negative, results were negative (no growth). On the rare occasion that one BI was positive and one BI was negative, it was assumed, with a 95% confidence level, that there was a 5.7 log reduction of spores. For facility decontamination, these results would be considered successful and significantly more effective than utilizing a liquid disinfectant solution.

Once the BIs were placed, the remaining unsealed HVAC cooling coils were shut off, allowing outside humidity to enter the space and raise humidity in the room to over 70%. The decontamination took place during the summer months, so ambient/outside humidity was naturally high. Once room humidity was verified in all areas to be above 65% for a minimum of 30 minutes, the HVAC was shut down and sealed and then the last entry doorway was sealed.

Day 2—Gassing

At approximately 16:45 (4:45 p.m.), the gas cylinders were opened and gas injection began. Chlorine dioxide gas was generated by passing a low-level chorine gas (2% chlorine/98% nitrogen) through solid sodium chlorite cartridges, which converts the chlorine to a 99.9% pure chlorine dioxide gas. Workers walked around the decontamination space carrying low-level safety sensors to locate any possible leaks in any of the plastic and duct tape sealing. This task was performed periodically to ensure worker safety. Chlorine dioxide gas has a low odor threshold (0.1 ppm), which coincides with the 0.1 ppm, eight-hour personal exposure level.

Gas injection ran continuously from 16:45 to 21:00 (4:45 p.m. to 9:00 p.m.) to accumulate a minimum dosage of 720 ppm-hours to achieve a 6-log reduction of spores (see Figure 1 for concentration readings and Figure 2 for dosages).

All concentrations were at or near the target of 1 mg/L, except for the pre-gown area (see Figure 1). This sample tubing had a leak that diluted the sample reading. The area was verified to be above concentration by visual inspection. A yellow-green color was observed inside the space, signifying the presence of chlorine dioxide gas. This inspection does not inform the user of the concentration; however, if the gas is highly visible, an experienced user knows the concentration is higher than the 1 mg/L target concentration.

After the dosage was reached, a team went up to the roof to unseal the air handling units (AHUs). At approximately 22:00 (10:15 p.m.), all AHUs were unsealed and turned on.

Aeration in the three sterile component staging areas was started at 21:00 (9:00 p.m.). These areas were identified to have no exhaust capabilities; therefore, a supplementary aeration system was set up in this area. This system consisted of four external blowers pulling air from the component stag-ing area and blowing it out the nearest rollup door to the plant exterior. All filling lines aerated in a normal amount of time. Safe levels of chlorine dioxide (0.1 ppm) were attained about 22:30 (10:30 p.m.) in all areas.

Around 23:00 (11:00 p.m.), three people entered the sterile facility and donned gowns following B&L procedures. The team removed the BIs, tub-ing, blowers, and fans and crated equipment. Then, the team used a low-level safety sensor to verify the gas concentration in all areas was below safe level. Once this was verified, all sealing plastic and tape were removed. The team exited the cleanroom at approximately 0:00 (12:00 a.m.). The remaining equipment was packed into the crates, and the team left the site at approximately 01:30 (1:30 a.m.). Finally, all BIs were incubated for 36 hours in the prepared culture media to test for growth. Table 2 lists the BI results.

When it comes to maintaining clean and fresh laundry, we often rely on a range of detergents and cleaning agents. However, there's one powerful yet often misunderstood solution that deserves a spotlight in the world of laundry care - chlorine dioxide tablets. While chlorine dioxide has garnered a reputation as a potent disinfectant, it's essential to understand how to use it safely and effectively for laundry and fabric cleaning.

Understanding Chlorine Dioxide

Chlorine dioxide (ClO2) is a chemical compound known for its remarkable ability to clean bacteria, viruses and fungi. It has been widely used in various industries, including water treatment, food processing, and medical applications, for its powerful disinfection properties.

Chlorine dioxide tablets are a popular option for laundry and fabric cleaning due to their convenience and effectiveness. When dissolved in water, these tablets release chlorine dioxide gas, which acts as a strong oxidizing agent, breaking down organic stains and killing microbes on fabrics.

Benefits of Chlorine Dioxide Tablets for Laundry

Using chlorine dioxide tablets for laundry and fabric cleaning offers several benefits

1. Powerful Disinfection: Chlorine dioxide effectively kills bacteria, viruses, and fungi that may be present in fabrics, leaving your laundry hygienically clean.
2. Odor Removal: Chlorine dioxide helps eliminate stubborn odors caused by bacteria and molds, leaving your laundry smelling fresh.
3. Color-Safe: Chlorine dioxide is generally safe for most colored fabrics when used according to instructions, as it doesn't cause significant fading or color loss.
4. Effective Stain Removal: Its powerful oxidizing properties help break down and remove tough stains like wine, blood, and grass.
5. Laundry Machine Cleaning: Chlorine dioxide tablets can also be used to clean and disinfect your washing machine, ensuring it remains free from harmful bacteria and molds.

Alternative Uses

Apart from laundry and fabric cleaning, chlorine dioxide tablets can be utilized for other purposes:

1. Surface Disinfection: Use chlorine dioxide to sanitize countertops, cutting boards, and bathroom surfaces.
2. Water Treatment: Chlorine dioxide tablets can purify water for camping or emergency situations, making it safe to drink

Safety Precautions

1. Follow Instructions Carefully: Always read and follow the manufacturer's instructions on the packaging of chlorine dioxide tablets. The instructions will provide guidance on the appropriate dosage and usage guidelines.
2. Use in Well-Ventilated Areas: Chlorine dioxide gas can be harmful when inhaled in large quantities. Ensure you use it in a well-ventilated area, preferably outdoors or in a room with open windows and good airflow.
3. Protective Gear: Take proper care when handling chlorine dioxide tablets to avoid direct contact with the skin or eyes.
4. Keep Away from Children and Pets: Store chlorine dioxide tablets in a secure location, out of reach of children and pets. Accidental ingestion or exposure can lead to serious health risks.
5. Avoid Mixing with Other Chemicals: Take precautions to not mix chlorine dioxide with other cleaning agents, it makes for a great cleaner, deodorizer and sanitizer all on its own!
6. Proper Dilution: Follow the recommended dilution ratios to ensure that the concentration of chlorine dioxide in the water is safe for fabric cleaning.

Method Application: Adding it to Your Front Load Washer

1. Consider using our Synergy Micro Wash Detergent (a fragrance-free detergent that is fully compatible with ClO2). This product is highly concentrated and requires only 1.5oz for a full load of laundry. Place this product in the dispenser tray of your washer.
2. Drop a 1g Synergy Envirotab Tablet into 16oz of warm water in a PET Bottle with cap.
3. As the water is filling and diluting your detergent, pour the ClO2 solution in with the detergent.
4. Wait for the cycle to run and expect odor-free cloths with it is done!

Chlorine dioxide tablets are a powerful tool for achieving fresh, hygienic, and stain-free laundry. When used with caution and following the recommended guidelines, they can provide effective disinfection and stain removal. However, it's vital to prioritize safety and ensure proper handling to avoid any adverse effects. With chlorine dioxide tablets as part of your laundry routine, you can enjoy clean and fresh-smelling fabrics without compromising on safety.

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