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Definition: Decontamination is a process or treatment that renders equipment, environmental surfaces, or biohazarardous waste safe to handle.
The effectiveness of decontamination ranges from high-level sterilization to simple cleaning with soap and water. Levels of decontamination include:
- Sterilization (high-level decontamination) uses a physical or chemical procedure to destroy all microbial life, including highly resistant bacterial endospores.
- Disinfection (intermediate-level decontamination) uses a liquid chemical to eliminate virtually all pathogenic microorganisms, with the exception of bacterial spores, on work surfaces and equipment.
- Cleaning (low-level decontamination) uses water, detergent, and some mechanical action such as scrubbing with a gloved hand or brush. Cleaning is often a required step before sterilization or disinfection, because it removes all material such as soil or organic material and reduces the number of microorganisms on an object.
Decontamination methods used in research include the following:
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Heat sterilization (wet or dry) |
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Wet heat sterilization (autoclaving) uses saturated steam under pressure of approximately 15 pounds per square inch to achieve a chamber temperature of at least 250°F (121°C) for a prescribed time (usually 30–60 minutes) to destroy all forms of microbial life.
Dry heat is less efficient than wet heat and requires longer times and higher temperatures to achieve sterilization.
- Typical uses: Sterilization of glassware by dry heat can usually be accomplished at 160°–170°C for periods of 2 to 4 hours.
- Precaution: Monitor wet and dry heat sterilizers on a regular basis using appropriate biological indicators [spore strips].
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Liquid disinfection |
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Liquid disinfectants can be generally classified as halogens, quaternary ammonium compounds, phenolics, aldehydes, and several other chemical compounds.
Liquid disinfectant effectiveness varies with the organism, concentration, contact time, and other conditions of use. Before a liquid disinfectant is selected, it must have been shown to be effective against the organism(s) present.
- Typical uses: Liquid disinfectants are used for surface decontamination and to decontaminate liquid wastes prior to disposal in the sanitary sewer.
- Precaution: The more chemically reactive a compound is, the more likely it is to be toxic and corrosive.
- Consult Summary of Disinfectants for recommended disinfectants, their uses, and requirements.
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Vapors and gases |
Vapors and gases, when used in closed systems and under controlled conditions of temperature and humidity, provide excellent disinfection. Agents in this category include the aerosol, vapor, or gas phase of chlorine dioxide, glutaraldehyde, para-formaldehyde, ethylene oxide, peracetic acid, and hydrogen peroxide.
- Typical uses: Vapors and gases are primarily used to decontaminate biosafety cabinets, animal rooms, and their associated systems, bulky or stationary equipment not suited to liquid disinfectants, instruments or optics that might be damaged by other decontamination methods, and rooms, buildings, and associated air-handling systems.
- Precautions: Due to their hazardous nature, contact EH&S Biosafety Division, (858) 534-5366, for special monitoring requirements if these compounds will be used.
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Radiation (ionizing or non-ionizing) |
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Ionizing radiation: Ionizing radiation will destroy microorganisms, but it's not a practical tool for laboratory use.
Non-ionizing radiation: The UV-C band of ultraviolet (UV) radiation contains wavelengths (250-270 nm, 265 is optimum) that are very effective in destroying most microorganisms in air and water and on surfaces. Organisms must be directly exposed to the UV light. Otherwise, dirt, dust, and shadows can protect organisms, limiting effectiveness.
- Typical uses: Ultraviolet radiation is used to reduce levels of airborne microorganisms in healthcare, food handling, and pharmaceutical production settings. UV is also used in biological safety cabinets and in some laboratory rooms to reduce surface contamination.
- Precautions: UV can cause burns to the eyes (photokeratitis) and skin of people exposed for even a short period of time. Follow these precautions:
- Activate UV lights only when the area is unoccupied.
- Use proper shielding when UV lamps are in use.
- Interlock UV lamps used for space decontamination with the general room or cabinet illumination, so that turning on the lights extinguishes the UV.
- Warn personnel who may be unfamiliar with the hazardous affects of UV radiation to their presence and appropriate precautions.
- Maintenance: Because UV lamp intensity or destructive power decreases with time, proper maintainance is critical for decontamination purposes. Perform this regular maintenance:
- Check lamp efficiency monthly with a UV meter or monitoring strip.
- Clean UV lamps every few weeks to prevent dust and dirt from accumulating, which drastically reduces their effectiveness.
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If you are a UCSD employee and have questions, contact EH&S Biosafety, (858) 534-5366.
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