Decontamination using Chlorine Dioxide in Food Plants
04/2022 Issue: Decontamination using Chlorine Dioxide in Food Plants
By Levi Farrell, ACE
Over the past couple of years, we have become very familiar with microbial control and the use of sanitizers. However, this is usually a surface wipe, a quick pump of liquid sanitizer onto your hands or at most an aerosol application. This is all fine and well, but for most food plants that isn’t enough to control harmful pathogens from contaminating surfaces, equipment and potentially your lunch.
Many sites went above and beyond and experienced a lot of production interruptions once a positive case of covid was reported. However, many cases of food borne illnesses still occur every year as a result of ineffective sanitation practices. Most of us are familiar with the concept of fumigation relating to insects and rodents. This process using Chlorine Dioxide is similar but with an entirely different target organism. Most FDA recalls and outbreaks focus on the big 3, salmonella, listeria and ecoli.
The main difference between decontamination and disinfecting is the level of control and achieving control in inaccessible areas. A log reduction is the number of 9’s after the decimel. For example, with the use of chlorine dioxide gas, we target a 6-log reduction. That written on paper is 99.9999%. This type of treatment also has a very different mode of action. Your liquid disinfectants work based off of contact dwell time, which is the amount of time the liquid sits on the surface before it evaporates. Chlorine dioxide gas penetrates the cell wall. Similar to insects, there are “adults” and “eggs” in the pathogen world. This is often referred to as live or active cells and spores or the inactive state. The aforementioned level of control applies to the level of spore control, which is much more challenging.
We monitor CD in PPM or parts per million. The accumulation of PPM over time is referred to as ppm hours. Depending on what you are trying to control, you may require a higher concentration over a longer period of time. The higher the ppm hours you accumulate, the greater log reduction you will see. Factors that weigh in on is cost of gas, temperature, time and humidity. Since CD gas is generated onsite, the process can be quite tedious. Another factor is UV light. UV light breaks down chlorine dioxide gas fairly quickly and may deplete concentrations. If you plan on conducting treatments during the day, it is recommended that windows are covered with dark polyethalene sheeting and interior lights be turned off prior to application.
When speaking with our customers, it is very important to identify all equipment and areas that are of concern. These treatments are very costly, so minimizing the foot print just to that area is important. It is also worth noting that during preparation, the entire area/piece of equipment must be sealed so that it is treated inside and out. Like any gas, CD gas will penetrate into equipment where a liquid cannot and offer a much better level of control
A recent treatment conducted for a client had some issues that were not foreseen during the initial site survey. Due to the interior and exterior temperature differential, severe positive pressure was being applied to the area. The area being treated had to be completely sealed with polyethalene sheeting with the exception of the West wall. Because of the amount of pressure, seals were constantly rupturing and needing repair. The additional 2 areas being treated were in concrete rooms. These rooms held the gas extremely well. While we were unable to maintain concentration in the entire area, equipment was treated separately. Fortunately, all equipment met or exceeded the required dosage.
Another important step similar to live insect bio-assays in fumigation is the use of biological indicators or BIs. Spores are placed on these small strips and sealed in a Tyvek cover, which are placed in key areas. The use of these along with the readings is the verification the treatment was successful.
The final step is critical. While aerating, removing seals and equipment, do not re-contaminate the area. You should have a team that works in the area in sterilized clothing, and a team that remains outside the area. It’s always best to work with the site contact and the micro team to ensure preventative steps are in place to reduce the risk of a reaccurance.