Disinfection involves the destruction of microorganisms, but not usually spores, on inanimate surfaces or objects. Disinfection is not sterilization. Sterilization describes a process that destroys or eliminates all forms of microbial life, including spores. Disinfection methods can involve the use of physical (e.g., heat or ultraviolet light) or chemical (e.g., disinfectants) processes to reduce, inactivate, or destroy pathogenic microorganisms.
Many factors can affect the effectiveness of the disinfection process. These include the microorganism being targeted, the organic and inorganic load present, the characteristics of the disinfectant (or disinfectant method) being used, as well as other factors such as temperature, pH, water hardness, relative humidity, and the physical nature of the object or surface being disinfected. For the use of physical disinfection methods, including heat, there are likely to be specific requirements and processes based on the situation and/or the disease agent involved.
A Typical Disinfection Process
- Select a Disinfectant: The first step is disinfectant selection. Determine and select a disinfectant registered by U.S. Environmental Protection Agency (EPA) for use against the microorganism(s) of interest and for the object or area that needs to be treated. Product labeling includes detailed information including the ingredients statement, warnings and precautionary statements, and directions for use. Disinfectants must be used according to their approved labels at the indicated dilution, labeled use, application method, contact time, and safety measures.
- Disinfection Preparation: Prepare fresh solutions of disinfectants daily, or as specified on the label. Some disinfectants can lose stability shortly after being prepared for use or when stored over long periods. Use of an outdated product may result in ineffective disinfection.
If a product is to be diluted, the label will provide specific mixing directions. Using the proper concentration is important to achieve the best results for each situation. Some products will have different dilutions depending on the intended use of the product (e.g., sanitizing, disinfecting, sterilizing). Disinfectants are tested and proven effective at the specified dilution provided on the label. The dilution listed on the label must be followed exactly unless a FIFRA Section 18 exemption allowing a different dilution (see Regulation of Disinfectants). Additionally, the use of disinfectants at higher concentrations than specified on the label may increase the hazard to personnel and to the environment. Conversely, over-dilution of a product may render the process ineffective to the target microorganism.
Personnel safety during disinfection preparation is essential. Gloves, eye protection and sometimes masks may be needed during this process. Consult the product label for any safety precautions; inform personnel of these safety measures.
- Application: Disinfectants must only be used for the item or area specified on the label. Additionally, the required application method and contact time will be provided. Application methods may involve spraying, fogging or misting, wiping, immersing, or mop-on methods. Appropriate safety measures (e.g., personal protective equipment) should be used during all disinfection processes; including the application process.
- Contact Time: One of the most important components of the disinfection procedures, regardless of the method chosen, is to allow adequate contact time. This is essential for the process to have the desired impact – destroying microorganisms. In some cases (e.g., when long contact times are required), the disinfectant may need to be reapplied in order to keep the surface “shiny” wet for the full required contact period.
- Rinse: Following the application (and appropriate contact time), items and areas should be thoroughly rinsed. Many chemical disinfectants can be harmful to animals and should be rinsed with potable water.
- Dry: Whenever possible, surfaces should be allowed to dry completely (if possible overnight). The drying process can also further aid in reducing or eliminating microorganisms through desiccation. Premises that have been cleaned and disinfected should have a period of downtime following disinfection. This involves the area being free of any animals or activity for a period of time to allow it to not only dry completely, but since the application of disinfectant solutions uniformly over large areas (e.g., ceilings, walls, floors) can be very difficult, adequate downtime helps to further reduce or eliminate any remaining microorganisms through desiccation.