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Clearance of Mold Remediation Undermined by Modern Use of Air Conditioning Systems

Updated: Nov 18, 2022

While humans spend most of their life indoors, indoor air quality must be maintained to reduce pollutants. Indoor air pollutants are among the leading factors for premature death, as the World Health Organization (WHO) estimates 1.6 million deaths annually as a result of indoor air pollutants. It is imperative that homes and workspaces maintain clean air, as humans are more susceptible to the effects of air pollution indoors.

According to the EPA, concentrations of some pollutants can be 2 to 5 times higher than concentrations outdoors. While the types of indoor air contaminants can vary greatly, mold is among the most common pollutants. As a result, mold can trigger allergies, damage materials, etc. One method of reducing mold exposure is by circulating stagnant air through air conditioning systems. However, the use of air conditioning systems (ACUs) has a greater effect on increasing spore count indoors than outdoor spores increasing indoor spore counts; ACUs facilitate the spread of mold spores through disturbance of surfaces as well as transferring spores suspended in the air.

Standards of Mold Remediation Clearance vs. Air Conditioning Systems

When suspecting mold, home and business owners often resort to mold remediation to resolve issues of mold growth and moisture intrusion. An affected region is typically cleared by inspectors using the standard method of comparison between the control and collected samples, where spore concentrations indoors must be lower than outdoor concentrations. This method was sufficient in successful mold clearance; however, the increasing use of air conditioning systems in buildings has rendered this method inaccurate.While air conditioning units ventilate stagnant air, mold spores may be relocated and spread throughout the property. Moreover, leaks in ACUs and air ducts provide sufficient moisture for mold growth. It is imperative that areas where water intrusion is present be inspected and remediated immediately. If left untreated, mold reservoirs can grow as soon as 24 to 48 hours according to the Federal Emergency Management Agency (FEMA). Additionally, if mold remediation is cleared, yet the ACU or ducts contain a leak, the source of moisture intrusion is not resolved and mold growth is able to perpetuate.

Source of Moisture

During mold remediation, mold spores suspended in the air and on surfaces may be remediated; however, the source of moisture may not be located allowing further damage and health consequences. While moisture sources may not always be easy to locate, a possible location to search is the ACU for potential leaks. Leaks can be resolved by licensed professionals; however, any exposure to moisture in the ACU allows for sufficient conditions for mold growth. Typically, the filters of air handler units as well as individual parts within the system should be routinely inspected. Failure to pinpoint the source of moisture facilitates further contamination, damage, and allergens by mold growth.


Although an inflicted region may be cleared by inspectors, failure to maintain conditions for mold prevention or inaccurately cleared mold remediation lead to negative consequences including but not limited to:

● Additional exposure to mold spores

● Allergies

● Growth and spread of mold spores

● Damage to organic materials

While mold concentrations outdoors may cause allergic reactions, even exposure to small amounts of mold indoors could be problematic for occupants within a building. Post remediation, a workspace should provide a healthy space and have regulated concentrations of mold. However, when indoor conditions are not remediated and maintained, mold spores continue to grow and spread. Inaccurately cleared mold remediation will create extensive damage to health and property, and require additional attention.

Maintaining Conditions to Prevent Mold Growth

Several steps may be taken to regulate conditions of mold growth prevention including:

● Using high-quality Merv 11 air filters on the air conditioning unit (ACU)

● Turn on AC fans 24/7 to filter air indoors

● Maintaining and scheduling visual check-ups from licensed professionals

for AC and air duct systems

● Regularly maintain surfaces containing dust

● Implement and utilize a humidistat, maintaining an indoor humidity

between 30-55% to prevent mold growth or dust mites

● Replace old carpets with new carpets or with wood/tile flooring

● Use a vacuum cleaner with a HEPA filter and anti-microbial wipes

on non-porous surfaces

When ensuring a space is remediated, maintaining such conditions is essential to preventing health consequences and/or damage. According to the EPA, humans approximately 90% of their lives indoors. Consequently, residential and commercial buildings must be kept at ideal conditions where indoor air quality is a top priority. Taking the steps listed above to stop mold growth and ensure the safety of the inhabitants within the building.

Take Away

When suspecting mold growth or water intrusion, mold inspections and remediation should be scheduled immediately to resolve any moisture issues. Typically issues of mold growth are resolved through inspection and remediation, then cleared by a qualified professional by

comparing the spore counts of indoor vs. outdoor concentrations.

However, this method may not be accurate in buildings utilizing air conditioning systems. ACUs can facilitate mold growth through leaks in the system and by disturbing and spreading mold spores around the subject building. In order to accurately remediate a building, ACUs must be inspected and maintained to prevent leaks. Leaks in ACUs allow sufficient conditions for mold growth and may disturb and circulate the mold spores throughout the subject building.

Failure to properly clear mold remediation will result in extensive damage to one’s health and property. In homes and workspaces, regular management of ACUs and areas of potential moisture intrusion should always be monitored and remediated immediately to prevent mold growth, as even limited concentrations of mold spores may cause allergies or other health problems. When occupants become sick, all areas within and adjacent to the home or office must be cleaned in addition to the area of remediation.

BNF Consulting, Inc. is a licensed mold inspection company that abides by New York State & US EPA regulations for mold inspection and testing. Does your home or business have a mold problem? Our company can provide a reliable mold inspection service to determine potential risks.

Call us today at 914-297-8335 for a free phone consultation!


About Authors:

Justin H. Joe, PhD, CIH, CSP, CPE, is a Certified Industrial Hygienist and

a principal consultant of BNF Consulting, Inc. Dr. Joe graduated from the University of Illinois at Urbana-Champaign with PhD and MS degrees in nuclear engineering. Dr. Joe has provided industrial hygiene consulting as a core function with his diverse background of experience and education.

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