The purpose of containment during mold removal is to prevent occupants and remediators exposure to mold and to limit the release of mold spores into the air and surroundings.
The size of the area helps determine the level of containment but a heavy infestation of black mold in a relatively small area could release more spores than a lighter growth of mold or mildew in a larger area so the choice of containment should be based on professional judgment.
Professional remediators should isolate the area using plastic sheeting (treated with flame retardant). The containment area must be maintained under negative pressure relative to surrounding areas. This will ensure that contaminated air does not flow into adjacent areas. This can be done with a HEPA-filtered fan unit exhausted outside of the building. For small, easily contained areas, an exhaust fan ducted to the outdoors can also be used. Remediators may also use air scrubbers (high-volume HEPA air filters) to reduce the concentrations of mold contaminants within the work area.
All supply and air vents, doors, chases, and risers within the containment area must be sealed with polyethylene sheeting to minimize the migration of contaminants to other parts of the building.
The containment area must be maintained under negative pressure relative to surrounding areas. This will ensure that contaminated air does not flow into adjacent areas. This can be done with a HEPA-filtered fan unit exhausted outside of the building. For small, easily contained areas, an exhaust fan ducted to the outdoors can also be used. The surfaces of all objects removed from the containment area should be rcleaned prior to removal.
A decontamination chamber or airlock should be constructed for entry into and out of the remediation area where workers change into their remediation gear: safety goggles, protective suits, gloves, and booties, as well as respirators. The chamber should be large enough to hold a waste container and allow a person to put on and remove PPE. All contaminated PPE, except respirators, should be placed in a sealed bag while in this chamber.
As an additional precaution, you may wish to hang plastic sheets over doorways between the containment area and other rooms in the house. It also makes sense to remove area rugs, particularly where workers will be walking back and forth, and to tape nonslip protective coverings over these paths. Smoke testing may be used to ascertain whether air is flowing from the containment area into other rooms.
In order to provide proper containment, air must be continuously blown out of the contained work area (and provisions made for air from the rest of the building to infiltrate the work area). Unless the exhausted air is HEPA-filtered, mold spores may move with wind into indoor environments close by.
Keep in mind that most moldy construction materials are considered rubbish, and there are no requirements for secured disposal, as there are for lead paint and asbestos. Of course, everything that gets thrown out is eventually attacked by microorganisms but that doesn’t mean you shouldn’t be cautious in the interest of protecting your neighbors. Tossing moldy materials into an unprotected dumpster can aerosolize contaminants. Moldy materials should therefore be sealed in heavy-duty plastic bags before removal from the containment area and disposal.
Mold Containment for Smaller Jobs
While it isn’t always possible for homeowners to create the containment conditions that professional remediators create, it’s important to to isolate the work area as much as possible. The enclosure around the moldy area should consist of a single layer of 6 mil, fire-retardant polyethylene sheeting. For the entrance, tack or tape two pieces of plastic sheeting to the top of the wood trim over entrances to the room to cover any open doorways. Each piece should cover approximately two-thirds of the opening.
Attach one piece to the top and right side of the doorway, and the other piece to the top and left side of the doorway. The section in the middle where the two pieces overlap will function as a partial air seal while also allowing you to enter and exit.
Alternatively, you can create a “booth” around your work area by arranging four spring-loaded rods vertically between the floor and ceiling and attaching horizontal pipes to the rods with hose clamps or duct tape. Then you can tape plastic sheets to the pipes to enclose the space. Again, leave an overlap between two of the pieces of plastic so you can enter and exit. In designing any kind of containment-like conditions, be sure that one wall of the isolated area has a window to the exterior, so a box fan can be used on exhaust. This will remove many of the spores that may become aerosolized when the mold is disturbed.
In most cases, after the mold growth has been eliminated, and with the fan still operating on exhaust, other room surfaces can be cleaned with a HEPA (high-efficiency particulate arrestance) vacuum to eliminate contaminated dust; nonporous surfaces can be damp-wiped and allowed to dry.