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Remediation Procedures for a Moldy Building / House
The objective in a mold remediation project is to physically remove colonization and mold-laden dusts. Because the objective is not to sterilize or disinfect, and because dead spores as well as live spores are allergens, the use of biocides and disinfectants is unnecessary unless infection is perceived as a health concern. The main steps involved in mold remediation include the physical removal of mold colonization and mold-laden dusts, dust and spore containment, and the use of appropriate protective equipment by knowledgeable workers.
Inspection
It is the job of the building owner/manager to hire an indoor environmental consultant (EC) to determine the extent of the mold colonization to be removed by cleaning. Currently there are no accreditation or registration of qualified environmental consultants. When selecting one, however, ensure that they have past experience in independent monitoring of mold remediations and publications in that area. The EC must be independent of the mold remediator, and should have the ability to perform on-site spore trap analysis and in turn be able to interpret the sampling results.
Ideally, the first step is to ensure that all sources of the moisture problem are found and stopped. Once the moisture source is controlled, it is the job of the EC to determine the degree and location of mold colonization, which may include opening of floor, wall, or ceiling structural components to estimate the extent of hidden mold growth. Microbial samples should be taken and analyzed by an accredited laboratory for comparison before and after cleaning. The only approved laboratories are those accredited by the American Industrial Hygiene Association in its Environmental Microbiology Laboratory Accreditation Program (AIHA/EMLAP).
The environmental consultant will work with the owner/manager to choose a qualified third party remediation contractor (RC). The EC will provide guidance and professional judgment, and will monitor the work activities of the RC. Once the size and location of the mold colonization is determined, the RC constructs the appropriate containment and assures the use of proper protective equipment by their workers.
Containment and Dust Suppression
The use of containment barriers, depressurizing methods, and dust suppression procedures during removal of moldy materials is necessary to prevent distribution of spores into clean areas. The extent of the colonized surface(s) will determine the type of containment methodology.
Source Removal Containment (general minimal visual growth: about 10 ft2)
To minimize the potential for aerosolization of spores, the colonized material can be completely covered with polyethylene sheeting, sticky sheeting, or an encapsulant before removal. The material should then be cut out in one piece, sealed in a disposal bag and removed. A high efficiency particulate air (HEPA) vacuum cleaner should be used to capture dust and debris and to achieve negative pressure around dusty sources.
Local Removal Containment (moderate visual growth: about 10 to 30 ft2)
With 10-20 ft2 of colonized material, the use of sticky sheeting can be used as described for source removal. In addition, a single-layer of polyethylene sheeting (mini-enclosure) can be used to isolate the work areas. A HEPA vacuum should be used to collect dust and debris.
Full Containment (extensive visual growth: about 30 ft2 and greater)
When removing moldy materials from a building with extensive mold growth, a depressurized containment and decontamination unit should be set up. This type of containment is similar to full containments used during large-scale asbestos remediations. The containment area should consist of two layers of 6-mil flame retardant polyethylene sheeting on all openings, including the heating, ventilation, and air conditioning system openings. Non-colonized objects should be covered by two layers of polyethylene sheeting.
In addition to the use of a HEPA vacuum, air filtration devices (AFDs or negative air machines) must be used to negatively pressurize the mold remediation work area from zones outside the containment barriers. Full containments achieve maximum isolation of the work area, by use of tri-chambered decontamination units, and by HEPA filtration (99.97% collection efficiency at 0.3 microns) of all air exhausted from the containment area.
Once the containment areas have passed visual and sampling clearance criteria, the containment barriers, protective barriers, decontamination units, and equipment shall be removed. Once broken down, the entire area, plus about 10 feet beyond critical barriers, should be HEPA vacuumed.
Personal Protective EquipmentIn general, when any type of mold remediation work is being done, whether large or small, the minimum requirements include at least an N95 respirator, gloves, and a disposable layer of clothing.
Respiratory Protection
With source containment, workers should utilize N95 respirators; however, P100 respirators may be recommended by the EC. Persons performing local removals should use the minimum of a P100 respirator. Those working within full containments should use full-face negative pressure P100 respirators that are equipped with a HEPA filter and organic vapor cartridge(s). Cartridges and filters should not be used longer than for one workday.
Protective Clothing
During source removal, disposable gloves should be used and disposable protective clothing may be recommended. Local removal requires that full body disposable clothing be used. Protective disposable clothing sets should consist of full-body coveralls, head covers, gloves, and 18-inch high boot type covers. For full containment areas, workers should wear two layers of disposable clothing over street clothes before entering the work area. All protective clothing should be secured at the wrists to prevent skin exposure.
Decontamination Procedures
Containment Entry
Only the environmental consultant, building owner, and remediation workers with proper certification and training may enter the containment areas. All personal protective equipment must be in place before entry into the containment areas.
All workers should pass through the decontamination unit before entering
the containment areas.
Containment Exit
To leave the containment area, a worker must first HEPA vacuum their protective clothing and respirator. The worker then should pass through the airlock into the equipment room of the decontamination unit. Once in the equipment room, the worker should remove the outer layer of protective clothing and place in an appropriate disposal bag. The worker should then step into the clean room and have the inner layer of protective clothing HEPA vacuumed. The respirator should be wiped off with a wet cloth and the inner layer of clothing disposed of in an appropriate bag. The worker can now exit the decontamination unit.
Remediation and Disposal
Removal of Moldy Materials
All porous materials that are visually moldy should be discarded and removed from the building. Once the materials are removed, the entire work area should be HEPA vacuumed until there is no visible dust. Remaining non-porous surfaces should be thoroughly damp wiped with chemically treated cloths or with limited tap water.
Wiping should begin with the ceiling, down the walls, to the floor and toward the containment entrance. Materials like wood (semi-porous) that are dry or wet rotted should be discarded; however, wood that is sound can by sanded, planed, refinished, and reused. Once the area has been damp wiped, the EC should inspect the area for residual fine dusts. Once the areas have passed the visual inspection, the areas will be designated as preliminarily cleared.
Disposal
Materials removed from the containment areas should be placed in disposal containers that consist of double bagging using labeled 6-mil polyethylene bags. The bags should be taped to form an airtight seal and labeled appropriately. Waste from the HEPA-filtered vacuums should be disposed of in the same manner. Non-rigid materials from the containment areas should be discarded as mold contaminated materials. All bags must be handled and disposed of as if they contain moldy compost and should be stored in a secure location until transport. The transport of wasted material should meet Department of Transportation (DOT), state, and local regulations and should be disposed of in an authorized landfill.
Sampling and Microbial Clearance
Once the area is believed to be “clean” and has passed the visual inspection of the EC, sampling should occur to achieve microbial clearance. Spore traps (number of samples to be determined by the EC) should be collected from work areas as in the outdoor air. The laboratory will then analyze the samples and the EC will interpret the data in terms of success of cleaning. Because there are no set rules for clearance, practical clearance criteria should be decided upon in the cleaning protocol beforehand.
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Following is a formula that can be used to determine air changes per hour:
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Air Changes Per Hour (ACH)=
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Cubic Feet of Air filtered by machine in 1 Hour
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Containment Size in Cubic Feet
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Example: Room size is 50' by 50' with a 10' ceiling. Negative air machine is rated at 2000 cfm (cubic feet per minute).
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ACH =
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2,000 cfm x 60 minutes/hour
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50' x 50' x 10'
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ACH =
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120,000
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25,000
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ACH =
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4.8
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The 4.8 changes per hour would exceed the 4 changes per hour specification. However, if the filters were allowed to get too dirty and the airflow was reduced to 1200 cfm, one machine would not provide the necessary air changes. (1,200 cfm x 60 = 72,000 cf per hour; 72,000/ 25,000 = 2.9 air changes per hour.) This is where air scrubbers have a distinct performance advantage over negative air machines since they are designed to withstand much more filter loading while maintaining high airflows. It is very possible on some jobs that one air scrubber can be used where it would require multiple negative air machines. |
