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Mold Course Chapter 5:

Large Areas and Other Special Concerns

  1. Remediating Large Areas of Mold Contamination
  2. Mold Remediation in Heating, Ventilation and Air Conditioning (HVAC) Systems
  3. Confined Spaces

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Lesson 1 - Remediating Large Areas of Mold Contamination

For large or complex mold remediation jobs, you may consider hiring professionals who have experience working on large mold remediation projects, particularly since extensive containment and PPE may be needed. Be sure to check references and ensure that the professional has experience working in mold remediation situations. Remediators should follow EPA mold remediation guidance or other government or professional remediation guidance. Building occupants need to be informed about what is going to happen, when it will happen and how they may be affected.

Full containment on a large job.
Full containment

Containment should be designed to prevent the movement of mold spores from one area of the building to another. This effort usually requires full containment using double layers of polyethylene sheeting and fans to create negative air pressure. A decontamination chamber or airlock should be used to separate the clean areas from the contaminated areas during entry into and exit from the remediation area. The entryways to the airlock from the outside and from the airlock to the main containment area should consist of a slit with covering flaps on the outside surface of each entry. Contaminated PPE, except respirators, should be sealed in bags while inside the containment exit chamber.

Workers should wear respirators until they are in the uncontaminated area, where the respirators can be removed. Disposable respirators can be thrown away and re-usable respirators can be put into a bag for cleaning. Full PPE may also be necessary during these operations and may consist of protective clothing and full-face or powered air purifying respirators (PAPR) with HEPA filters. Protective clothing should include head and foot coverings with all gaps sealed with duct tape or the equivalent.

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Lesson 2 - Mold Remediation in Heating, Ventilation and Air Conditioning (HVAC) Systems

Mold remediation involving a heating, ventilation and air conditioning (HVAC) system should be done only by professionals experienced in working with HVAC systems. Professionals may have several different methods and techniques for approaching HVAC remediation. As with the rest of a mold remediation project, professional judgment is required when working with HVAC systems, and professionals may use materials, methods and techniques not mentioned in this course.

An HVAC system found to be contaminated with mold should be turned off and not used until the system has been remediated; using a mold-contaminated HVAC system may spread mold throughout the building and increase the exposure of building occupants. (There may be some exceptions or instances when all or part or the HVAC system can be run, based on professional judgment, if there is no risk of increasing occupant or worker exposure). If possible, the HVAC system should be remediated during off hours when the building is not in use.

Effective containment of the area served by the ventilation system is important to avoid the spread of mold and mold-contaminated materials. All intakes and supply vents should be sealed with plastic and tape, and negative air pressure should be maintained in work areas. (A fan can be used.) Contaminated porous materials in the HVAC system should be bagged and removed. Materials that can be cleaned should be vacuumed with a HEPA vacuum or cleaned with a moist cloth and detergent solution. All items should be dried promptly.

If you consider duct cleaning, first consult EPA's guide Should You Have the Air Ducts in Your Home Cleaned? See the Resource List.

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Lesson 3 - Confined Spaces

Confined spaces include pipe chases (areas within and under buildings where steam and utility pipes are run) and valve pits (areas below grade that contain utility shut-off valves). Working in confined areas presents numerous challenges. Movement and communication are difficult and, if a problem arises, immediate exit from the area may be impossible.

The air in some confined spaces may be contaminated or low in oxygen, posing significant health risks for workers. Efficient rescue of an injured worker may be difficult or impossible. Poor lighting may result in increased injuries. Because exposures may be greatly magnified in a confined space, workers must use a higher level of PPE than they would when working in a more accessible area.

Worker safety must be carefully considered when deciding whether to use disinfectants or biocides because confined spaces may increase the potential for exposure. In general, work in confined spaces should be conducted only by trained professionals who have the equipment required by OSHA to deal with the inherent dangers in this type of environment.

Before remediating mold in a confined space, the area should be evaluated for atmosphere and toxic substances. If there is any chance of low oxygen, the area should be tested using the appropriate equipment. The testing equipment should be kept on site and used periodically to ensure an adequate oxygen supply. If the area is sealed off from the rest of the building to prevent the spread of mold spores, oxygen testing should be conducted again after the area has been sealed. A frequent contaminant in crawlspaces and pipe chases of older buildings is asbestos; other chemicals such as natural gas and solvents can also be found in some of these spaces. These materials must be identified and dealt with properly to prevent worker exposure.

Once the hazards have been identified, procedures for working in the confined space should be included in the remediation plan. Special consideration should be given to:

  • Who will be allowed into the area
  • How communications will be maintained
  • What materials can be taken into or used in the space
  • What safety equipment is necessary

Only individuals trained in the hazards associated with that space should be allowed to enter. An attendant should be posted outside of the confined space area to summon help if necessary. The area should be well lit so that work can be conducted efficiently and injuries avoided.

In conducting the mold remediation, every effort should be made to keep dust and mold out of the air. This can be done by using moist techniques, such as a damp cloth or pad, for mold removal and by bagging the material in the confined space for later removal. Mold levels are likely to be high in a confined space, so PPE should be selected accordingly. Most cases will require full PPE, including skin and eye protection and full respiratory protection using a full-face respirator or a powered air purifying respirator (PAPR) with a HEPA filter. The presence of asbestos may require other PPE for workers as well as monitoring and medical evaluation.

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