Remediation

Before taking remedial action, it is important to identify the contamination sources and the expected results of the remediation. Remediation techniques for microbial contamination depend on the surfaces where the contamination exists. Non-porous HVAC surfaces can be cleaned. However, steps should be taken not only to eradicate the growth, but to insure its containment during the remediation process. The US Environmental Protection Agency (USEPA) and the North American Insulation Manufacturers Association (NAIMA) recommend that any water-damaged porous material, such as insulation, acting an an amplifier, be removed rather than cleaned.

The remediation process consists of 4 elements: Identifying and correcting the source of contamination; Controlling the contaminated area to prevent spreading of fungi; Source removal of the fungi, contaminated dust, debris and other unwanted materials within the ventilation system; and Treating the affected areas with an antimicrobial chemical, if necessary.

Antimicrobial Chemical

Antimicrobial chemicals (biocides) are identified in 6 classes by the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Of these 6 classes, 4 are applicable to HVAC systems. These classes are: Sterilants, which eliminates ALL forms of microbial life; Disinfectants, which eliminates infectious pathogenic bacteria; Sanitizers, which reduces microbial contaminants; and Fungicides, which destroys fungi that are pathogenic to humans or animals on inanimate surfaces.

In order for the biocides to be effective, the surfaces to be treated must be clean and thoroughly wetted with the biocide. The surfaces should not be wet for more than 24 hours or the moisture may promote new fungal activity. After remediation services the surfaces should be dry. All interior HVAC system surfaces must meet coverage and exposure criteria defined by the biocide manufacturer. The remediation firms should provide the means to insure and verify the results of sanitizing.

The use of biocides must be considered toxic, and as such, exposure must be minimized as much as possible. Workers and building occupants must be protected from short- and long-term exposures.

The Decision to use Biocides

Since fungi is constantly present, air samples and wipe samples will always yield positive results. The decision to use biocides should be based on a risk assessment (health risks of exposure to mold amplification) and economics (cost benefits of remediating the mold).