THE COHEN GROUP
  Environmental Health & Safety Consulting Services

The Cohen Group Newsletter - Volume 5  Issue 2, Article 2.  April 2003

Mold Remediation Alternatives

Julie Wellings, CIH and Tim Bormann, CIH

A question we are often asked:   Do I need to remove the mold or can it be "treated"?  In this article, we introduce one of the more controversial issues in dealing with mold-impacted materials, i.e., the application and effectiveness of various non-removal remediation methods.   We will briefly discuss the potential pros and cons of removal and non-removal alternatives that may be employed where mold is present. 

REMOVAL:  Visible mold is most typically remediated through the removal of impacted “soft” building materials (e.g., drywall, ceiling tiles, carpet and insulation) and cleanup of residual mold particulate using a HEPA vacuum.  However, some porous materials (such as wood and concrete) serve as mold reservoirs but are difficult to remove and/or thoroughly clean.  In addition, disturbance of mold-impacted materials will release mold particulate (e.g., spores) into the air and the work must therefore be conducted under controlled conditions, i.e., with the HVAC system shut down and with the areas physically contained and equipped with HEPA-filtration equipment.

BIOCIDES:  Visible mold may be treated with a “biocide” (disinfectant) to kill fungal growth.  However, the effectiveness of biocides varies from compound to compound as well as with the concentration and duration of biocide application relative to the amount of mold growth.  The type of material to which the biocide is applied is also a factor.  For example, the use of biocide may be practical on wood substrates, but not on gypsum materials.   In addition, biocides may present a health hazard to the applicator during application, and residual biocide may cause air quality, material degradation and/or material compatibility problems.  Further, even where mold spores are completely deactivated, other allergenic mold particulates (e.g., cell fragments / proteins) may be released into the air. 

COATINGS:  Coatings, typically acrylic, can be applied (by brushing or spraying) to seal surfaces and protect against moist, humid conditions that promote mold growth.  However, these materials are not biocides (are not used to remediate mold) and most manufacturers state that their product must be applied to clean surfaces free of mildew and mold.  The coatings are useful for sealing of both porous and non-porous surfaces and some may be used as a mold-resistant paint system on plaster, wallboard, drywall and wood surfaces. 

UVC EMITTERS:  UVC (ultraviolet light, “C” range) emitters can be used to remediate mold growth.  Historically, low UVC output and hazardous ozone production have precluded the use of UVC emitters in most situations. Some newer emitters, however, are designed for high output under a range of environmental conditions and do not emit the UVC wavelength that converts oxygen to ozone.   However, the UVC units must be installed in relatively close proximity to mold-impacted surfaces, effective elimination of gross mold growth may require 30 or more days of continuous operation at each impacted location, and non-spore mold particulates (e.g., cell fragments /proteins) may be released into the air.  UVC emitters appear to be best suited for ongoing source control following remediation of gross mold growth.

DRY-ICE:  In this method, particles of dry ice are extruded from a dry ice pelletizer. The pelletizer utilizes small (rice-sized) particles of dry ice (solid carbon dioxide, CO₂) as the primary cleaning media. Using air pressure, these particles of dry ice are directed at high velocity towards the surface being cleaned. Upon impacting, the dry ice particles sublime, converting from a solid into a gas, leaving only the removed surface contaminant for disposal.  This method has been used with some success on wood surfaces but is not effective on gypsum material.  The method is also not useful for hard-to-reach areas. In addition, the method can produce high concentrations of airborne spores and should only be used under proper work area containment.

DRY HEAT:  This method is applied by heating surfaces to approximately 80 ⁰C (176 ⁰F), disrupting the cellular function of living fungal organisms.  To heat surfaces, the hot air is ducted into the contained area and distributed via fans.  The method is not without significant hazards including damage to architectural components and building systems, fire, release of particulates, etc.  Heating may not be effective in remediating gross contamination and is most useful for sterilization of surfaces after gross removal of mold has been completed.