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Cleaning Mold, Removal Tips and Safety Precautions

Summary of Remediation Guidelines:

While there are no government regulations describing methods to properly remediate indoor mold contaminated environments, the New York City Department of Health wrote general guidelines in 2000, based on the consensus of recognized experts in the field. Similar guidelines have since been developed by the EPA, IICRC, ACGIH, OSHA, and AIHA, all similar to the 2000 NYC Guidelines. These other agencies recommend that in addition to estimating the area having visible mold, you should also consider the possibility of hidden mold, the density of the growth, reservoirs of settled spores, occupant sensitivity, and cost-benefit analysis. The judgment of a qualified safety and health professional is emphasized in the final determination of precautionary measures to properly remediate.

  • Repair of the defects that led to water accumulation (or elevated humidity) should be conducted prior to fungal remediation, or fungal growth will recur.
  • People performing renovation/ cleaning of widespread fungal contamination may be at risk of exposure to microbials capable of: a) triggering allergic reactions, causing rhinitis (runny nose), eye irritations, coughs, congestion, and/ or aggravation of asthma; b) producing mycotoxicosis related to exposure to toxin-producing molds from the genera Aspergillus, Penicillium, Fusarium, Trichoderma, Stachybotrys or Memnoniella; or c) causing Organic Dust Toxic Syndrome (flu-like symptoms after a single heavy exposure to dust contaminated with microbials) or Hypersensitivity Pneumonitis (after repeated exposures to the same causative agent).
  • The goal of remediation is to remove or clean contaminated materials in a way that prevents the emission of fungi and dust contaminated with fungi from leaving a work area and entering an occupied or non-abatement area, while protecting the health of workers performing the abatement.
  • It is the responsibility of the people conducting remediation to ensure the methods enacted are adequate.

  • The simplest and most expedient remediation that reasonably, properly and safely removes fungal contamination should be used.
    The remediation safety precautions recommended are based on the amount of mold present, as outlined below:
    • Level I: Small Isolated Areas(10 sq. ft. or less) – e.g., ceiling tiles, small areas on walls.
      • Trained building staff may perform the cleanup.
      • Recommended measures include:
        • Misting the area (or cover with contact paper) for dust suppression
        • Using a N95 respirator (dust mask available at hardware stores), gloves and eye protection.
        • Remediate while area is unoccupied.
        • Vacate adjacent spaces if occupied by susceptible groups.
        • Bag contaminated materials at the site for disposal.
        • Clean surrounding surfaces with a damp cloth to remove the settled dust in the area.
    • Level II: Mid-Sized Isolated Areas(10 – 30 sq. ft.) – e.g., individual wallboard panels.
      • Trained building staff may perform the cleanup.
      • Recommended measures include:
        • Mist area (or cover with contact paper) for dust suppression.
        • Use a N95 respirator (dust mask available at hardware stores), gloves, and eye protection.
        • Remediate while area is unoccupied.
        • Bag contaminated materials.
        • Vacate adjacent spaces if occupied by susceptible groups*.
        • Install critical barriers (containment)**
        • Bag contaminated materials at the site for disposal.
        • HEPA vacuum and clean with damp cloth in any affected area.
    • Level V: Mold Remediation of Ventilation Systems(furnace, ducts and registers).

      • A Small Isolated Area of Contamination (Less than 10sq. feet) in the HVAC System.
        • Use a N95 disposable respirator, gloves, and eye protection.
        • Remediation should take place while area(s) are unoccupied.
        • Vacate adjacent spaces if occupied by susceptible groups and/or mop with detergent solution for post-remedial cleanup.
      • Areas of Contamination (more than 10 square ft.) in the HVAC System.

    * Susceptible groups include infants and children, the elderly, immune compromised or immune suppressed patients, pregnant women, individuals with existing respiratory conditions, such as allergies, hypersensitivity pneumonitis or asthma.

    ** Critical barriers are two layers of polyethylene sheeting that block all openings, fixtures, and HVAC system components. The purpose is to prevent the spread of contaminants beyond containment area.


    Please see the New York City Department of Health (2008) Guidelines on Assessment and Remediation of Fungi in Indoor Environments or the Environmental Protection Agency document Mold Remediation in Schools and Commercial Buildings.

    Extensive contamination, particularly if heating, ventilating, air conditioning (HVAC) systems or large occupied spaces are involved, should be assessed by an experienced safety and health professional and remediated by personnel with training and experience in handling environmentally contaminated materials. Effective communication with building occupants is an essential component of all remedial efforts.

    Fungi in buildings may cause or exacerbate symptoms of allergies (such as wheezing, chest tightness, shortness of breath, nasal congestion, and eye irritation), especially in persons who have a history of allergic diseases (such as asthma and rhinitis). Decisions about removing individuals from an affected area should be based on the results of a medical evaluation, and be made on a case-by-case basis. Except in cases of widespread fungal contamination that are linked to illnesses throughout a building, building-wide evacuation is not indicated.

    For further information or testing, contact a qualified environmental health professional (certified industrial hygienist or an indoor environmental professional with training and experience).

    Additional Important Mold Removal Tips:

    • Porous materials (e.g., carpet, sheetrock) from which mold growth cannot be adequately cleaned must be removed from the building.
    • Boric acid (borax) or hydrogen peroxide is very effective at killing mold. These products do not have an odor and are recommended for people with chemical sensitivities. However, small minorities of people have reported sensitivities to boric acid.
    • Vacuuming may temporarily increase exposure to mold spores. The spores can pass through ordinary vacuum bags and remain suspended in the air for hours or days. Central vacuums that vent outside are recommended, or vacuums fitted with HEPA filters and micro-filtration vacuum bags to help minimize this exposure.
    • Carpet cleaning should be performed by trained professionals that utilize hot water extraction. Ensure that the cleaned carpets dry out in less than 24 hours. Chemical cleaning methods can leave a residue that attracts soil and other contaminants.
    • A HEPA (High Efficiency Particulate Air) air cleaner, with or without a charcoal filter, can be utilized in addition to source removal and ventilation to remove unwanted airborne contaminants. However, relying on an air cleaner alone to solve a significant mold problem is insufficient.

    Safety precautions when cleaning mold

    • Spores are easily released into the air when moldy material is dried out. Mold counts are typically 10 to 1000 times higher than background levels during the cleaning of mold damaged materials. Take steps to protect your health during cleanup. When working on mold patches, always protect yourself with an appropriate facemask. For small localized areas, use an inexpensive disposable face mask (N95), which you can buy at a hardware store; for larger areas, use a full-face respirator with an approved, disposable HEPA filter, which you can obtain from a safety supply store.
    • Never mix ammonia detergent with bleach, as it can release dangerous chlorine gas.
    • Always ventilate the work area when using bleach (Clorox). If possible, open two opposite outside doors or windows to create a crosswind. A fan will increase airflow. Position it (the fan) so that the Clorox fumes are directed away from the breathing zone.
    • Never use a gasoline engine indoors (e.g. pressure washer, generator, etc.)—You could expose yourself and your family to carbon monoxide.
    • If you see moisture condensing on the windows or walls, it is possible there is a combustion problem in your home. It is important to have sufficient fresh air available for fuel burning appliances, such as the furnace, water heater, stove/range, clothes dryer, and fireplace. A shortage of air for these appliances can result in back drafting of dangerous gases such as carbon monoxide into the home. Have your local utility company or a professional heating contractor inspect your fuel-burning appliances annually.

    Hidden Mold

    • In some cases, indoor mold growth may not be visible. It is possible that mold is growing on hidden surfaces, such as on the back side of dry wall, behind wallpaper, behind paneling, the top side of ceiling tiles, the underside of carpets and pads, etc. Investigating hidden mold problems can be more difficult and will require caution when the investigation involves disturbing potential sites of mold growth. Make sure to use personal protective equipment or consult an environmental professional for help (e.g., an industrial hygienist or certified indoor air quality consultant).

    Finally a reliable mold test kit