Follow Your Nose: CD's Best Safety Feature

While all decontaminating agents are by nature dangerous, chlorine dioxide (CD) gas has many traits which make it the safest method available. The best safety feature with CD is that it is self-alerting.  Chlorine dioxide gas has a discernible odor at safe levels, allowing you time to shut down the system and address the situation safely if it is smelled. Other agents, such as Ethylene Oxide (EtO) and Vapor Phase Hydrogen Peroxide (VPHP), cannot be sensed until you are exposed to extremely high concentrations.  This dangerous trait is why natural gas is given a sulfur-like odor additive, to act as an alert. VPHP users (and surrounding colleagues) become aware of a harmful exposure only when coughing and choking occurs, therefore a reliance on external sensors to prevent adverse health effects is more necessary.  With CD, this need for external equipment is not as strong because of its odor.  CD has an odor threshold at or below the 8-hour Time Weighted Average (TWA), so the user is self-alerted to exposure at a low level and the reliance on external sensors is not as imperative as it is with VPHP.  This makes CD safer for both the user, and any surrounding personnel who may be working nearby.

Visit our Safety page to learn more important differences between chlorine dioxide and hydrogen peroxide.

Is Chlorine Dioxide Carcinogenic?

A major factor in choosing a decontamination method is safety. All decontamination agents are dangerous as this is their function. However, gaseous chlorine dioxide can be used more safely than other fumigation methods due to its chemical properties and safety profile. One example of this is that chlorine dioxide gas is not a carcinogen. Formaldehyde is “known to be a human carcinogen” as described by the US National Toxicology Program. Formaldehyde was once a widely used method for decontamination, but its classification as a carcinogen has limited its use and caused it to be banned by some health agencies. The ACGIH designates vapor phase hydrogen peroxide (VPHP) as an A3, Confirmed Animal Carcinogen with Unknown Relevance to Humans. Chlorine dioxide gas is not considered to be carcinogenic, with no health organization listing CD as a carcinogen of any kind. In fact, it is used to treat fruits, vegetables, poultry, and other food products. Chlorine dioxide has also been used in the treatment of drinking water since the 1920’s both domestically and internationally.

Do you have safety concerns about the use of chlorine dioxide for decontamination? Attend our CD Gas 101 webinar on September 18th to ask questions and learn more.

Biological Safety Cabinet (BSC) Decontamination

The Class III Biological Safety Cabinet (BSC) is a gas-tight enclosure designed for work with highly infectious microbiological agents and for the conduct of hazardous operations and provides maximum protection for the environment and the worker.  A Class III BSC is typically decontaminated on a periodic basis and always before filter change out and repairs. Formaldehyde and chlorine dioxide gas are the only approved decontamination methods by NSF International. However, chlorine dioxide gas provides a much quicker cycle time than formaldehyde, is not a carcinogen, and does not leave a residue.

The Tufts New England Regional Biosafety Laboratory (RBL) is dedicated to the study of existing and emerging infectious diseases, toxin mediated diseases, and medical countermeasures important to biodefense. The facility’s two main decontamination choices are vapor-phase hydrogen peroxide (VPHP) and chlorine dioxide (CD) gas. Both agents are known to be efficacious, and both are sterilants. VPHP has been used longer, and many papers have been published on the process. Some issues of concern were that VPHP condenses and, when it does, the droplets become more aggressive or concentrated. Because of the increased concentrations, it has been documented to damage painted surfaces, epoxy surfaces, and electronics. Additionally, VPHP vapors have been shown to have limited distribution and penetration abilities. CD easily penetrates and distributes into all spaces. It covers an entire room, penetrates deeply into equipment, and gets into the hard-to-reach places. Setup is simple and requires very few extras (only 1 or 2 fans and a portable humidifier). Based on the needs to decontaminate this RBL, CD gas was the best choice as it provided complete decontamination of all surfaces within the spaces and inside the Class III BSC.


The Class III BSC can be decontaminated as part of the room (by opening the gull wing door), or it can be decontaminated on its own through use of the built-in connectors. The components needed are RH probe, mix box (which contains a humidity generator), blower motor, DC/AC controller, pressure relief scrubber, and the Minidox generator. The CD gas concentration is monitored via a gas sample port. This hose is connected to the Minidox, which then, on the basis of real-time readings, activated the gas injection system as needed. The scrubber removes any CD gas during this process. A standard cycle of 5 mg/L for 30 minutes of exposure is often used for Class III BSCs. However, due to the nature of this particular facility’s work, the cycle time was extended to 45 to 60 minutes. All biological indicators (BIs) were repeatedly killed, and no issues of corrosion were evident. All components continue to remain free of any imperfections. Due to that, chlorine dioxide gas is now the method of choice for the decontamination of Class III BSCs.

To read more about Tufts New England Regional Biosafety Laboratory’s utilization of chlorine dioxide gas for both BSC and room decontamination, click here. 

The Myth of Corrosion

Chlorine dioxide (CD) is an oxidizer, as is hydrogen peroxide, ozone, bleach, and many other decontaminating agents. However, CD gas is the gentlest on materials among those options, due to its lower oxidation potential. A higher oxidation potential means it is a stronger oxidizer and more corrosive. As shown in Table 1, chlorine dioxide has an oxidation potential of 0.95V, which is lower than other commonly used oxidizing biocides. CD is not as aggressive an oxidizer (oxidation potential data) as chlorine, ozone, peracetic acid, peroxide, or bleach — and it should be non-corrosive to common materials of construction.

Table 1: Oxidation Potential of Common Biocides

While scientifically less corrosive, chlorine dioxide gas has a bad reputation due to the link with chlorine as well as the other chlorine dioxide products that lack the purity that our process uses. Other methods of generating chlorine dioxide mix an acid and a base which forms a chlorine dioxide solution which is then off-gassed to fumigate a space.  That generation method produces two acidic components, acidified sodium chlorite and chlorous acid, alongside chlorine dioxide which makes these methods more corrosive. Our method of generating pure chlorine dioxide gas is accomplished by passing a low concentration chlorine gas through a proprietary sodium chlorite cartridge to convert the chlorine gas into pure chlorine dioxide gas. This allows our process to be safe when decontaminating stainless steel, galvanized metals, anodized aluminum, epoxy surfaces, electronics, and the most common materials of construction. Typically, if water will not corrode an item, neither will our CD.

To learn more about material compatibility, click here. If you have a specific item of concern, send us some samples. We offer free material testing* to give confidence that chlorine dioxide gas will be safe on your equipment, products, components, tools, etc.

*Testing is free for small items or batches. For large items or extended testing, please call (908) 236-4100. Shipping not included.

Decontamination Chambers

A Decontamination Chamber is designed for use in any laboratory, pharmaceutical, manufacturing, research or surgical setting. It provides a rapid and highly effective method to sterilize computers, electronics, medical devices, instruments, and components at ambient temperatures. It also provides a cost-effective method to decontaminate parts, supplies, and equipment entering a “sterile” or “clean” facility without the need for a large, expensive, energy consuming sterilizer. It allows the removal of items from a dirty or BSL level area to a clean area without the concern for cross contamination.

Chlorine dioxide gas is a highly effective EPA-registered sterilant. It is a true gas which naturally fills the space it is contained within, no matter the shape or amount of items within. CD gas has more consistent kill and quicker cycles than Vapor Phase Hydrogen Peroxide (VPHP). Decontamination time can be under 1.5 hours for a 150 ft3 chamber. The chlorine dioxide process is easy to validate due to the repeatable cycle, tight process control, and highly accurate sterilant monitoring system.  A run record is produced that contains process parameters.

For many applications, a Decontamination Chamber can effectively replace a bulk autoclave inside a facility. Decontamination Chambers can save energy and money compared to bulk autoclaves in terms of steam usage, water usage, electricity usage, maintenance costs, replacement costs, cost of capital equipment, and footprint. Chlorine dioxide gas is capable of decontaminating electronics, racks, cages, HEPA filters, plastics, and the outsides of bedding and feed bags.  Autoclaves are still the best suited to decontaminate dense organic materials such as bedding and feed. As many facilities have multiple autoclaves, the easiest decision might be to implement both an autoclave and a decon chamber to fulfill all of your facility’s needs. The equipment is available in a variety of sizes including a dual door option. We also fully integrate with BetterBuilt, Lynx, Tecniplast, Girton, Schyler, Buxton Scientific, and other manufacturers.

To learn more, visit our product page or request a decontamination chamber quote.

Inactivation of Beta-Lactams

Beta-lactam antibiotics are, by definition, a class of antibiotics which contain a beta-lactam ring in their structure. They are split into various groups depending upon their base structure, with the main groups being penicillins, carbapenems, cephalosporins, and monobactams. Allergic reactions to beta-lactams can be life-threatening. Due to the large number of individuals allergic, the pharmaceutical industry explored a method for their inactivation.   This research was performed such that a contaminated area could be treated and re-used for the future production of non-beta-lactam compounds. This would allow companies to “recycle” beta-lactam facilities instead of demolishing them upon the completion of production.

Testing was conducted using chlorine dioxide gas at various concentrations and exposure times in an effort to achieve the pharmaceutical manufacturer’s required 3-log (99.9%) reduction of eight different beta-lactams on various surfaces. Nine inactivation cycles were tested, with five passing the acceptance criteria beneath U.S. Food and Drug Administration (FDA)-required 0.03 ppm residue detection level. Successful inactivation cycles which achieved a 3-log reduction of all eight beta-lactam compounds all had cumulative exposures of over 7,240 ppm-hours. Further studies validated this dosage for providing a 3-log reduction of all eight beta-lactams tested.

In 2008, a leading pharmaceutical company was looking to renovate a 33-room facility, that had been used for the production of an Imipenem-based product, into a new training facility. Because positive samples for beta-lactams were found in multiple rooms and inside the ductwork, the entire production facility along with its HVAC was to be treated. Chlorine dioxide gas was injected into 24 locations and sampled from 12 locations to ensure fast and thorough distribution.  To ensure that gas was getting into the HVAC system, the recirculation blower was bumped throughout the process. Upon completion, the area was swabbed by the pharmaceutical company. All swabs came back negative proving that no beta-lactams remained, making the treatment a success.  Since that initial facility treatment in 2008, chlorine dioxide gas has been used for this specific application at a number of other facilities worldwide.

To learn more, click here.

How Does Chlorine Dioxide React with Water?

In most cases, before a decontamination occurs, the environment undergoes a wet cleaning to remove dirt and organic material.  This residual water can present a challenge for some decontamination methods.  One example being Vapor Phase Hydrogen Peroxide (VPHP) because it dilutes and breaks down in water.  So for that method to be effective, the area must be completely dry before use.  Depending on the application, drying the environment can be a lengthy process which adds a prohibitive amount of time to the cycle.

Chlorine dioxide (CD) gas is water soluble, allowing it to maintain its sterilization efficacy within water.  Unlike chlorine, CD gas does not form hydrochloric acid and maintains a neutral pH. In wet environments, chlorine dioxide can decontaminate any remaining water as well as the surfaces beneath.  This eliminates the need to wait until the environment is completely dry before decontamination occurs, in turn, decreasing the overall downtime.

One application where this has a real world effect is within decontamination chambers.  The use of decontamination chambers is becoming more prevalent within research facilities and clean rooms.  Within vivaria where space is extremely valuable, these chambers are sometimes included as part of a dual-use rack washer/decontamination chamber unit.  Within this application, if the system is run as a rack washer, the amount of water at the bottom of the chamber afterwards can take hours to completely dry out.  Being CD gas is not affected by water, it can be used within a dual-use chamber immediately after a wash cycle.  This can save your facility hours of time and allow the savings in facility footprint to become a viable option.  It also allows a contaminated facility the ability to become completely decontaminated as there’s no worry for residual water rendering the process ineffective.

Amplicon Inactivation

The rapid growth of DNA sequencing in laboratories is resulting in the increased use of PCR readers.  As a result,  researchers are making advances in science and medicine, but not without new challenges. One challenge is that the integrity of the results can be affected if amplicon residues contaminate part of the PCR reader. This contamination could cause improper analysis of subsequent samples. Mitigation of this problem requires amplicons to be inactivated from all surfaces of the PCR reader, including all cracks and crevices of the equipment.

Chlorine dioxide gas cycles have been validated with multiple PCR reader manufacturers in order to clear the reader from residual amplicons which can cause inaccurate results and readings.  The validation consisted of a series of cycles with varying chlorine dioxide gas dosages that were tested to achieve an inactivation of the amplicons. The verification process also confirmed that the equipment was not corroded as a result of the treatment cycles.

ClorDiSys Solutions, Inc performs amplicon inactivation work as part of its contract sterilization and decontamination services.  Two manufacturers of PCR readers have their customers send equipment to our facility before having it returned to the manufacturer for maintenance and repair.  At our facility, our contract sterilization team treats the units to eliminate any residual amplicons and blood-borne pathogens. This treatment allows the equipment to be safely handled by the manufacturers' maintenance department.

For more information, please read our Application Note on Amplicon Inactivation here.

Case Study: The Musculoskeletal Transplant Foundation (MTF) Isolator

The Musculoskeletal Transplant Foundation (MTF) is the nation’s leading tissue bank. MTF designed and validated the use of isolators in the production of DBX Demineralized Bone Matrix (DBX) putty. DBX Putty is the combination of demineralized bone and sodium hyaluronate for use during surgical application. Since the DBX putty is introduced into the body, it must be produced and packaged under aseptic conditions and procedures. Aseptic technique refers to efforts to maintain a sterile field during a procedure to prevent infection. In order to maintain the highest aseptic techniques, it was decided to move the DBX Putty process to isolators for their ease of use in cleaning and decontamination. The process whether conducted in a clean room, biological safety cabinet, or an isolator is largely the same with the exception of the decontamination cycle.

In order for this process to be economically feasible, the decontamination cycle had to take less than 2 hours.  If the decontamination time exceeded 2 hours, then it would not be cost effective enough to warrant the change from clean room processing to isolation processing. The choice was between vapor phase hydrogen peroxide and chlorine dioxide gas. Both methods are registered with the US-EPA as sterilants, and both have been used in clean room environments and in isolators. The VPHP process produced varying amounts of condensation with potential for poor distribution and penetration abilities into gaps and small openings. Based on these limitations, chlorine dioxide, a true gas at room temperatures, was chosen due to its fast cycle times and evidence of its effectiveness.  With the reduced cycle times, MTF’s decision to move forward with isolators became feasible. The isolators eliminated the need for using 2.5 ISO 4 clean rooms and provided true aseptic processing.  The chlorine dioxide gas generator and isolators worked together to provide a simple and seamless systems integration.

To learn more about the Musculoskeletal Transplant Foundation’s selection, design, and validation of isolators for aseptic processing with chlorine dioxide gas, read Nick Barbu and Robert Zwick’s article in Pharmaceutical Engineering here.

Material Compatibility - Electronics

Material compatibility remains one of the largest question marks for those looking to use chlorine dioxide gas, and there’s a lot of conflicting information on the topic.  Chlorine dioxide gas cannot be stored and shipped, so it must be generated at the point of use.  The method of generation, and its resulting purity, has a great impact on the material compatibility of the chlorine dioxide gas product being used.  One of the first large scale decontamination projects utilizing chlorine dioxide gas was the oft referenced Hart Senate Building decon performed in November 2001.   It was performed by a company who previously used its CD gas technology for controlling odors in oil wells. As material compatibility was never an issue in this previous application, they used a less refined process of generation which contained acidic byproducts. When used in the Hart Senate Building, some material issues and corrosion occurred. ClorDiSys was established after this, and our chlorine dioxide gas is generated by passing a low concentration chlorine gas through a proprietary sodium chlorite cartridge to convert the chlorine gas into pure chlorine dioxide gas. Our process does not leave a residue and does not require any additional clean up once the gas has left the space.

ClorDiSys has done studies with electronics and found that they stand up well after multiple exposures. Computers have been exposed to the gas for over 25 cycles and have been fully functioning afterward. In fact, chlorine dioxide gas was chosen to decontaminate the inner chambers of a $3,000,000 Transmission Electron Microscope over hydrogen peroxide vapor because of its superior material compatibility as proven through manufacturer testing. The US Environmental Protection Agency (EPA) commissioned a study exposing computers to chlorine dioxide and hydrogen peroxide over the course of 6 months. Below are the test results showing chlorine dioxide had the lowest amount of failures.

Not all chlorine dioxide gas products are the same, and we understand the hesitation considering some of the information available regarding corrosion.  That’s why we offer free* material testing to give confidence that our chlorine dioxide gas will be safe on your materials and sensitive items.

* Testing is free for a reasonable amount of items.  Shipping not included

Ultraviolet Light in HVAC Systems

Mold, mildew, and dangerous diseases, such as Anthrax, Influenza, Measles, Smallpox, and Tuberculosis, are often spread through airborne transmission. Mold spores easily disperse, wreaking havoc in the new environments they land upon. A solution to continuously combat harmful organisms is the introduction of ultraviolet light disinfection. Ultraviolet light is divided into UV-A, UV-B and UV-C rays. It is the wavelengths in the UV-C spectrum, specifically 265 nm, that offers the greatest germicidal potential.  When a microorganism is exposed, the nuclei of the cells are altered due to photolytic processes. This process prevents further replication and causes cell death.

Ultraviolet light disinfection systems can be placed directly within HVAC ducts to both eliminate and prevent mold, mildew, and other organisms from forming and spreading.  Unlike HEPA filters that solely trap organisms, allowing them to flourish and possibly be re-released into the environment, UV-C kills organisms, eliminating that risk. Placing UV-C disinfection units within the HVAC system provides a continuous disinfection cycle with no harmful effect to anyone present in the space.  Units can be placed in the supply and the return to maximize the benefits.  Units placed in the return ducts have an even greater benefit, because the slower air velocity allows for additional exposure time. Ultraviolet light disinfection is an easy, hands-off, chemical-free way to reduce the risk of mold and mildew from developing and the spread of disease causing airborne organisms.


Attend the upcoming UV Light for Healthcare webinar on July 19th and UV Light for the Life Science and Pharmaceutical Industries on August 7th to learn more.

Can Chlorine Dioxide be used with Organic Foods?

ClorDiSys is occasionally asked if chlorine dioxide can be used in organic foods or in organic processing facilities. The short answer is yes.  More specifically, according to 7 CFR part 205, SUBCHAPTER M—ORGANIC FOODS PRODUCTION ACT PROVISIONS, the use of chlorine dioxide is allowed, but it comes with some restrictions. Its use is permitted for Livestock Management Tools and Production Aids, for Processing Sanitizers and Cleaners, and for Crop Management Tools and Production Aids. The common restriction across all three applications is the residual chlorine levels in any final rinse water or water in direct contact with food products or animals. The water cannot exceed the maximum residual disinfectant limit under the Safe Drinking Water Act (0.8 mg/L or 800 ppb). Reference the label of the product you are using to establish proper use corresponding with such restrictions. Visit the websites below for additional information to see if your organic operation qualifies for chlorine dioxide usage.

REFERENCES

• Organic Materials Review Institute, https://www.omri.org/generic-material/chlorine-dioxide

• Title 7 Agriculture → Subtitle B → Chapter I → Subchapter M → Part 205—NATIONAL ORGANIC PROGRAM https://www.gpo.gov/fdsys/granule/CFR-2011-title7-vol3/CFR-2011-title7-vol3-part205/content-detail.html

Case Study: Decontamination of Tented Equipment or Area

Food production facilities are facing greater scrutiny from both the public and the government to provide safe foods. Advances in environmental monitoring and microbial sampling have brought to light the shortcomings of the food industry’s sanitation methods. While there are many reasons for recurring contamination by a persistent pathogen, insufficient cleaning and decontamination is the most common. ClorDiSys Decontamination Services can be utilized for a variety of applications within the food industry from tented pieces of equipment up to entire facilities. Tenting an area is an application that we’re seeing more of lately, especially in facilities that have more of an open design and floor plan.

One example of this application is when our service team decontaminated a confectionery facility’s roaster. The roaster had caught fire and was extinguished by the fire department.  Worried the water used to put out the fire contained organisms which could contaminate their production line, this company wanted to clean the equipment before production started again.  Some of the equipment’s interior was not easily accessible for the in-house sanitation team, so once the majority of cocoa powder was removed, the company opted to decontaminate with chlorine dioxide gas. That equipment was tented and fumigated, as the rest of the room was not deemed a concern. The setup and decontamination of the roughly 8,000 ft3 space took place in 1 day and successfully provided a 6-log sporicidal reduction of all surfaces within the equipment.

ClorDiSys’ Decontamination Services can be arranged for contamination response or preventive control needs. Visit our team at booth #609 at the IAFP Annual Meeting in Salt Lake City July 8-11th to learn more!

Case Study: Used Equipment Decontamination

Our Decontamination Service Team recently completed a decontamination of a used bacon slicing line for a food company.  Because it was a used piece of equipment, the company did not want to bring it into the facility without being decontaminated first. This was not only to preserve the current sterility of their production area, but also to ensure safe food production once the line was in use. The slicing line was placed within a trailer which provided a sealed chamber for safe decontamination. 10 biological indicators were placed within the trailer and equipment in order to show that a 6-log reduction had been achieved. Once the trailer was sealed, the decontamination started.  The entire setup and decontamination took 4 hours from start to finish, when it was safe to open the trailer and bring the equipment into the production area. All biological indicators came back negative for growth verifying that the decontamination was successful. Production was able to start on the bacon slicing line shortly after being installed within the production area, and the company has been safely producing food since.

Contaminated piece of equipment in your facility? Call ClorDiSys at (908) 236-4100 or email the Decontamination Service Team at service@clordisys.com.

Continuous vs. Pulsed UV-C

Not all ultraviolet disinfection is alike. In fact, not all ultraviolet light is alike. Ultraviolet light is divided into UV-A, UV-B, and UV-C rays. It is the wavelengths in the UV-C spectrum which offer the greatest germicidal potential. Some UV disinfection systems, like xenon pulse UV, use the full spectrum of ultraviolet light to disperse germ-killing energy. It is claimed that the xenon pulse is a more effective way to kill harmful bacteria because of its similarities to punching a wall, more punches will weaken it better than one. However, light is not a fist. It is a form of energy, and continual energy is more effective than turning it on and turning it off. Additionally, bulbs generating UV-A, UV-B, and UV-C wavelengths are inherently less effective in disinfection than continuous UV-C.

The US Veterans Administration commissioned an infection prevention research team led by Curtis Donskey, M.D., to conduct an independent study of continuous ultraviolet disinfection versus xenon pulse UV disinfection. The study tested a continuous UV-C robot which was run for the same length of time from the same point in the room as a pulsed xenon (PU-UV) unit.  The results showed surprisingly low pathogen kill rates for the pulsed xenon device, about .5 log for both C.diff and VRE, even as close as 4 feet.  The continuous UV-C robot demonstrated a much higher CFU reduction for the pathogens C. difficile, MRSA and VRE.  The study states, “PX-UV was less effective than continuous UV-C in reducing pathogen recovery on glass slides with a 10-minute exposure time in similar hospital rooms” and “the UV-C device achieved significantly greater log10 CFU reductions than the PX-UV device”. Not only did the continuous UV-C robot in the study show much stronger disinfectant results, but that it was not run for its entire cycle time. The study calls attention to the dangers of bold claims and trying to complete a disinfectant procedure too quickly.

Chart from VA Donskey study: Study results showing log reductions achieved by a UV-C and pulsed xenon devices
when run for the same time (10 min.) at the same distance from glass microscope slides (4 ft).
(PRNewsFoto/Infection Prevention Technologies)

To read more on the comparison of these two technologies, click here.