Part 4 – Space decontamination and summary

This section provides an overview of the procedures for decontaminating or sterilizing spaces and all items within those spaces, a process commonly referred to as fumigation. This process typically employs one of three chemicals: hydrogen peroxide, formaldehyde, or chlorine dioxide. The application of these chemicals generally involves the use of specialized equipment designed to release them as either gas or vapor, thereby ensuring penetration throughout the designated area or equipment within that area. The room needs to be airtight; otherwise, gas or vapor will escape, nullifying the effectiveness of the procedure.

The first method, formaldehyde, is the most traditional method employed for fumigation. Historically, formaldehyde gas was generated from liquid formalin through the addition of another chemical, a practice now deemed hazardous due to the immediate release of gas while individuals are still present. Modern practice has shifted to utilizing paraformaldehyde, a solid that, when heated, vaporizes to release formaldehyde. The permissible exposure limit (PEL) for formaldehyde is 9.75 parts per million (ppm), while the threshold limit value (TLV) and short-term exposure level (STEL) stand at 0.3 ppm, categorizing it as a hazardous substance. Notable advantages include its efficacy as a powerful decontaminant, its non-corrosive properties concerning metals and electronics, and the relative ease of generation with the appropriate heating device. Conversely, disadvantages include its classification as a probable human carcinogen, its potential to cause acute respiratory irritation, and the necessity for neutralization following use. Due to its carcinogenicity, formaldehyde gas is being phased out and is no longer allowed to be used in many countries.

The vapor phase hydrogen peroxide method is widely recognized as the most popular approach for decontaminating spaces. This technique employs equipment to generate vapor from a concentrated 30% hydrogen peroxide solution. The permissible exposure level for this substance is 1.0 ppm, with a STEL of 75 ppm. Its benefits encompass effectiveness against viruses, bacteria, and spores, as well as the environmentally benign end products of water and oxygen, which negate the need for neutralization. However, it presents challenges as it is acutely toxic at elevated concentrations and can react with certain surfaces, including galvanized steel and porous materials such as paper. Additional information regarding this method is available online.

Chlorine dioxide, the final method discussed, is produced using specific machinery designed for generating this gas. It possesses a PEL of 0.1 ppm and a TLV/STEL of 0.3 ppm. Advantages of this compound include its efficacy against a broad spectrum of viruses, bacteria, and spores, its rapid and natural breakdown with no residual effects, and its effectiveness on both porous and non-porous surfaces. Nevertheless, it has certain limitations: it is unstable, necessitating continuous generation, requires careful maintenance of humidity, and may adversely affect particular metal surfaces. For further details regarding this method, please refer to the relevant online resources.

The validation of these fumigation methods aligns closely with that of the autoclave, utilizing both chemical and biological indicators. Typically, validation is conducted using paper strips that contain chemicals that change color upon exposure to the gas or that are impregnated with spores. Every fumigation procedure employing any of these methods must undergo such validation to ensure that the gas or vapor has adequately penetrated the entire space and effectively neutralized microorganisms.

In summary, it is vital to acknowledge that no disinfectant is universally ideal. Each disinfectant possesses distinct strengths and limitations, and comprehending these factors is essential for effective application within your facility. Various factors, including the inherent resistance of microorganisms to disinfectants, influence the efficacy of a specific disinfectant.

Autoclaves serve as effective sterilization devices by employing wet heat in conjunction with appropriate time, pressure, and temperature parameters. It is noted that damp heat is significantly more efficient than dry heat. Validation serves to confirm that the processes of decontamination, disinfection, or sterilization have been executed thoroughly and have met the intended objectives.

Thank you for your attention to this lesson on infection control via decontamination and sterilization. Please complete the quiz to remind you of some of the important principles discussed.