ATLANTA — While the mold remediation industry has produced a variety of approaches and voluntary guidelines, no U.S. federal government standards exist to define the processes or procedures needed to control or eliminate indoor fungal growth or fungal hazards. This leads to work practices and methods that vary greatly, even if projects are very similar, notes the Indoor Air Quality Association (IAQA).

One of the remediation procedures not consistently applied is the use of blowers and fans to create a pressure differential between the work area and surrounding areas. This procedure typically creates a space that is negatively pressurized compared to the non-contaminated or less-contaminated areas. These machines are often referred to as negative air machines (NAMs). In certain circumstances, NAMs are being turned off prior to clearance or post remediation verification (PVR) air sampling.

“This practice could be considered to be inconsistent with other remediation practices designed to protect the non-work areas from contamination from airborne or settled mold spores,” said Kent Rawhouser, president of IAQA.

IAQA has released a new white paper, “The Use of Negative Air Machines in Mold Remediation,” to help identify gaps in current industry knowledge and practice. The paper can be downloaded for free at

A task group was charged with determining if NAMs used to create a negative pressure contaminant should be either “on” or “off” for the PRV process and clearance sampling.

IAQA found that “the determination of whether a NAM is in operation during the collection of PRV samples should be evaluated on a case-by-case basis by the competent person who should document their decision and rationale.”

“With regard to air sampling, there is no published evidence that supports the contention that turning a NAM off at the end of the removal process will result in more realistic occupancy conditions,” Rawhouser said. “Both the ‘NAM on’ safety and health premise, and the ‘NAM off’ more accurate PRV sampling premise lack scientific data supporting them and require further research.”

As part of the paper, IAQA developed several recommendations. These include:

• Sharing this document with IAQ industry partners, as well as others with a material interest in mold remediation, to foster further discussions.

• Supporting the need for research and development toward a scientifically valid and industry accepted means by which PRV sampling is performed and evaluated.

• Supporting the need for research on particle profiling and potential exposures, both inside and outside the work area, while NAMs are running in order to improve the overall understanding of particle dynamics, the specifics of exposure, and the potential for cross-contamination.

• Supporting the need for research into whether post-remediation clearance sampling, particularly spore trap sampling, has any measurable merit in determining the efficiency of the remediation process.

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Publication date: 11/3/2014

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