VHP Safety Basics

A research technician enters a freshly decontaminated sterilization room to prepare or collect implements for research procedures. Almost immediately her nose and throat feel a tingling irritation, then she begins coughing and feeling a shortness of breath. In a few minutes she begins experiencing a stinging sensation on her skin, and her eyes are watering and burning to the point that seeing is difficult. She is trying to find the door to get out and thinking that she didn’t see or smell anything out of the ordinary upon entering the room. What went wrong?

Vapor phase hydrogen peroxide decontamination technology is relatively new, having been available since 1991.1 Vaporized hydrogen peroxide (VHP), or hydrogen peroxide vapor (HPV), is gaining popularity, and we are seeing rapid expansion of its use in everything from biological safety cabinets to animal rooms. In fact, HPV is challenging formaldehyde, a widely used sterilizing agent with many associated hazards, as the sterilizing agent of choice, and you can easily find information on its use for equipment decontamination, its efficacy and material compatibility, and some of the pros and cons of HPV compared to formaldehyde.

Most of us have heard of hydrogen peroxide and probably purchased it occasionally at the local pharmacy. Maybe your mom used it to clean out a small wound, cut, or scrape when you were a child. The commonly sold over-the-counter (OTC) product is typically a 3 percent aqueous solution of hydrogen peroxide. The product used in vapor phase hydrogen peroxide decontamination is much more potent. Solutions used in typical VHP decontamination processes contains more than 30 percent hydrogen peroxide, or at least 10 times more than the OTC product. The concentrated hydrogen peroxide is vaporized in self-contained portable generators using proprietary and patented methods. These generators are available from a couple of different companies and in several configurations depending on the size of the room or equipment to be decontaminated. Most applications involve sterile manufacturing and/or packaging of pharmaceuticals or medical devices; the VHP generators are relatively small and operate in a closed-loop system. The goal here is to prevent contamination of products by environmental microorganisms.

Research applications can run the gamut from decontaminating tools or equipment before removal from biological safety level 3 or 4 laboratories to entire rooms. Work usually involves pathogens, and the primary concerns are to protect the researchers and to prevent cross-contamination between experiments. Reduction of environmental microbial contamination can also be targeted in the case of care and breeding of specific pathogen-free animals. When large rooms are decontaminated, the ventilation system is used to maintain the desired pressure balance and to aid in the decontamination cycle. Usually the fresh air makeup is shut off, and in many cases the air handling system is used at the end of the cycle to flush out the room. Regardless of the configuration and construction materials used, the room must be well sealed during decontamination to prevent exposure of workers in adjacent areas.

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