As with environmental control strategies, the strategies available for decontaminating equipment are highly chemical-specific and situation-dependent. Effective decontamination methods differ based on chemical type, contamination route, and type of equipment/surface. Decontamination approaches include:59
- Physical removal of gross and residual contamination to a relatively reasonable level on contaminated surfaces in accordance with State and Federal guidance
- Inactivation of contaminants by chemical detoxification or disinfection/ sterilization
- A combination of both physical and chemical means
Physical contaminant removal. In many cases, gross contamination can be removed by dislodging/displacing, rinsing, or wiping off, and/or evaporation. Contaminants that can be removed by physical means include:
- Loose contaminants such as dusts and vapors. These may cling to equipment and responders or become trapped in fabrics. They can be removed with water or a liquid rinse.
- Adhering contaminants such as glues, cements, resins, and muds. These can be removed by scraping, brushing, and wiping; removal may be enhanced via solidifying or freezing (e.g., using dry ice or ice water), adsorption or absorption (e.g., with powdered lime or kitty litter), or melting.
- Volatile liquids. These can be removed by evaporation followed by a water rinse; evaporation may be enhanced by using steam jets. Here, care must be taken to prevent responder inhalation of vaporized chemicals.
Chemical contaminant detoxification. Inactivation/detoxification can be achieved by wash/rinse processes using cleaning solutions that utilize one or more of the following approaches:
- Rinsing. Rinsing removes contaminants through dilution and solubilization and may follow dissolving and surfactant treatments.
- Surfactants. Surfactants augment physical cleaning methods by reducing adhesion forces between contaminants and the surface being cleaned, and by preventing redeposit of the contaminants. Household detergents are common surfactants. Some detergents can be used with organic solvents to improve the dissolving and dispersal of contaminants into the solvent.
- Contaminant dissolution. Surface contaminants can be chemically removed from equipment by dissolving them in a solvent. The solvent must be chemically compatible with the equipment being cleaned, and care must be taken in selecting, using, and disposing of organic solvents that may be flammable or themselves potentially toxic.
- Solidification. Solidifying liquid or gel contaminants can enhance their physical removal. Mechanisms of solidification are: (1) moisture removal through the use of absorbents such as clay or powdered lime; (2) chemical reactions via polymerization catalysts and chemical reagents; and (3) freezing using ice water.
Decontamination methods vary in their effectiveness for removing different substances. The chosen decontamination method should be safe, effective, and compatible with the chemical released.59 Potential safety risks arise from methods that are chemically incompatible with the substance being removed (i.e., a decontamination reagent may react with the contaminant to produce an explosion, heat, or toxic products) or with the cloth or equipment being decontaminated (e.g., some organic solvents can permeate and/or degrade protective clothing), or that may pose a direct health hazard to workers (e.g., vapors from chemical decontamination solutions may be hazardous if inhaled, or they may be flammable). Factors such as cost, availability, and ease of implementation will also influence the selection of a decontamination method. Information provided by a RP via EPCRA-mandated notifications should indicate safe and efficient decontamination strategies.
While surface contaminants may be easy to detect and remove, contaminants that have permeated a material are often difficult or impossible to detect and remove, and may cause unexpected exposures later in time.
The effectiveness of any method should be assessed at the beginning of a decontamination program and continue periodically throughout the program. If contaminated materials are not being removed or are penetrating protective clothing, the decontamination program must be revised.
Footnotes
59. U.S Coast Guard. (2005). Hazardous Materials Response Special Teams Capabilities and Contact Handbook.