The exhaust ductwork in a laboratory at a major pharmaceutical company in North Carolina needed replacement. Since the ductwork was used to exhaust BSCs for testing on HIV and HCV, special precautions would be required during the demolition. These special precautions would add cost, complexity, as well as a level of risk to the demolition crew. The typical method of demolition is to have the construction crew wear protective suits with proper PPE and masks. Holes would be drilled or sections cut out from the ductwork and and the inside of the ductwork then sprayed or wiped down with sterilizing agents. The area beneath the ductwork would then need to be decontaminated with sterilizing agents to remove any of the contaminants that accidentally escaped. For proper decontamination to occur, the sterilizing agent would need to reach all surfaces inside the ductwork, at the proper concentration, for the time specified on its label. Because of the complexity of having contractors remove contaminated ductwork, the company decided that a fumigation style decontamination should be performed.

There are typically considered three methods of fumigation for areas such as rooms. Of these, formaldehyde and vapor phase hydrogen peroxide would not be able to accomplish that amount of ductwork decontamination. Formaldehyde is listed as a carcinogen and it leaves residues. Vapor phase hydrogen peroxide would break back down to a liquid because of the length of ducts and temperature gradients. The HEPA housings would also add additional challenges. The pharmaceutical company was familiar with the application of gaseous chlorine dioxide for area decontamination and chose to apply it for this ductwork decontamination. ClorDiSys Solutions, Inc. was called in to fumigate the contaminated ductwork with chlorine dioxide gas.

CHLORINE DIOXIDE
Although chlorine dioxide (CD) has “chlorine” in its name, its chemistry is radically different from that of chlorine. CD oxygenates products rather than chlorinating them and thus trihalomethane (THM) formation does not occur.¹ Therefore, unlike chlorine, CD does not produce environmentally undesirable organic compounds containing chlorine.

Chlorine dioxide is a true gas at normal use temperatures and therefore is not susceptible to condensation issues and temperature gradients. It has a yellowishgreen color, which allows its concentration to be precisely monitored and controlled by a UV-VIS spectrophotometer. This allows tight process control from beginning to end of a decontamination cycle.

Chlorine dioxide has been recognized for its disinfecting properties. Gaseous CD has been shown to be more effective than liquid CD when applied in equal concentrations and times.² Chlorine dioxide, in both gaseous and aqueous phase, is a strong oxidizing agent and has about 2.5 times the oxidation capacity of chlorine. ³ Additionally, CD gas has been approved for use as a sterilant/decontaminate by the U.S. EPA. Both gaseous and aqueous phase CD has been shown to be an effective sanitizing agent that has broad and high biocidal effectiveness. Aqueous CD has been reported to effectively inactivate bacteria^4,5,6 including pathogens,^7,8 viruses,^9,10 bacterial spores,^11,12 and algae.¹³