Hazards of Mold in Your Ductwork

Mold contamination within air duct systems can pose detrimental health effects to building occupants if left uncorrected.  If mold exists within your air ducts make a plan to investigate the source of the problem, isolate the problem area, and remove the contaminants.

Understanding Mold

Molds are part of the natural environment. Molds are fungi that can be found anywhere – inside or outside – throughout the year. About 1,000 species of mold can be found in the United States, with more than 100,000 known species worldwide.

When excessive moisture or water accumulates indoors, mold growth often will occur, particularly if the moisture problem remains uncorrected. While it is impossible to eliminate all molds and mold spores, controlling moisture can control indoor mold growth.  Molds are usually not a problem unless mold spores land on a damp spot and begin growing. They digest whatever they land on in order to survive. There are molds that grow on wood, paper, carpet, foods and insulation, while other molds feed on the everyday dust and dirt.

Since mold requires water to grow, it is important to investigate the source of the moisture to prevent mold growth.

Hazards of Mold in Your Ductwork

Ventilation systems are designed to distribute a recirculate air within a home.  If mold growth is within the ventilation system, or near an air intake, mold spores can be spread throughout a home.

“Toxic mold syndrome” remains controversial and unproven, but experts agree that it’s best to limit exposure to molds.  The most likely adverse reaction to mold is a respiratory allergic reaction in mold-sensitive people. These reactions are similar to other respiratory allergies, causing sneezing, watery eyes, nasal discharge and congestion.

Cleaning Air Ducts

Consider having the air ducts in your home cleaned if there visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system.

There are several important points to understand concerning mold detection in heating and cooling systems:

  • Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.
  • You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation.
  • If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.
  • If the conditions causing the mold growth in the first place are not corrected, mold growth will recur.

Dangers of Air Duct Cleaning Chemicals

Air duct cleaning service providers may tell you that they need to apply a chemical biocide to the inside of your ducts to kill bacteria (germs), and fungi (mold) and prevent future biological growth.   Careful consideration should be taken before allowing the application of chemicals within your air ducts.  Due to the varying ranges of temperature, humidity and air turbulence there are very few chemicals that are approved for the use within ventilation systems.

Chemical Off Gassing

Organic chemicals are widely used as ingredients in cleaning and sanitizing products.  Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids.   Even a nearly odorless material can cause significant problems when re-circulated through air ducts in a closed environment.  VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects.

NADCA’s Position Regarding the Use of Antimicrobials

The National Air Duct Cleaners Association’s new position regarding the use of antimicrobial chemicals is as follows: “At this point in time, until EPA clarifies their position, NADCA does not recommend the use of any sanitizer or disinfectant products in air ducts.” This position was adopted to generate awareness among NADCA members of the potential legal liabilities they face by selling and applying antimicrobial chemicals. This is strictly a matter of managing legal risks. NADCA’s position deals specifically with sanitizers and disinfectants, not with any other product claims. Also, this position covers only air ducts, not HVAC components such as coils

No EPA Registered Products for Fiberglass Air Ducts

There are no products that are currently registered by EPA as biocides for use on fiberglass duct board or fiberglass lined ducts so it is important to determine if sections of your system contain these materials before permitting the application of any biocide.

If  You Choose to Use Chemicals in your Air Duct Cleaning Project

  • Review the product sheet showing usage and application of the product.
  • Review the Material Safety Data Sheet (MSDS) to understand if chemicals will cause any health or property concerns.
  • Review the Fact sheet on the product classification being applied.

If You Have a Problem Related to Chemicals Applied Within Your Air Ducts

  • Open doors and windows to ventilate the area with fresh air.
  • Operate the fan of the HVAC system
  • Exit the premises if negatively affected.
  • Contact and Industrial Hygienist to discuss the problem.  Be sure to have a copy of the MSDS.

How to Remove Pet Urine Odor from Air Ducts

Pet urine within the air ducts is an extremely unpleasant odor.   Sometimes trouble shooting where the pet urine odor is coming from can be quite difficult.  Here are some great instructions on how to remove pet urine odor from air ducts.

Locating the Sources

Before you can correct a pet urine problem you have to identify all of the areas affected.  Sometimes it can be difficult to isolate or identify source of the pet urine odor.  One of the easiest methods of locating where pets have urinated is through the use of a UV black light.  First darken the room, and then shine the UV black light near vent register openings, pet urine stains will glow in the dark.

Cleaning the Surrounding Areas

As pets urinate into the vent registers, the urine is likely to collect around the carpet or hardwood floor near the air vent register opening.  If you do not clean the areas around the air vent register opening the scent of the urine will cause the pet to instinctively re-soil the area.

One of the best methods for removing the odor is to use baking soda and white vinegar.  Prior to using baking soda and white vinegar, be sure to check with your flooring manufacturer to see if it will affect your floors finish.  Never use ammonia or ammonia based cleaning products.  While ammonia is a good cleaning product, one of the components of pet urine is ammonia, and the odor of the ammonia can lead your pet to instinctively re-soil the area.

DO NOT spray cleaning chemicals into the air ducts, only specific chemicals may be used within air ducts.  Your ventilation system is designed to redistribute air and can potentially distribute the volatile cleaning fumes throughout the home.  If you have accidently poured chemicals within the air ducts, open the doors and windows and call a duct cleaning professional.

Duct Cleaning

After you have cleaned the surrounding area of the air vent registers, hire a professional air duct cleaning contractor.  Debris within the air ducts will harbor pet urine odor.  As the heating and air conditioner is in operation, pet urine odor can distribute throughout the entire home.  An duct cleaning contractor will be able to access the HVAC system and help you to restore the HVAC system to its proper condition.

Ventilation System Mold Remediator

Local HVAC System Cleaning Contractor Achieves Prestigious Certification

WASHINGTON, DC – Local contractors Edward Frisk, and Jason Erb of Ductworks, Inc. have successfully completed the training and examination process to be certified as a Ventilation System Mold Remediator. The certification, which is administered by NADCA – The HVAC Inspection, Maintenance and Restoration Association, is recognized worldwide as the hallmark of the HVAC industry’s most qualified and reliable mold remediation professionals.

“While achieving the VSMR certification takes commitment on the part of an HVAC professional, the certification itself is a commitment to consumers of reliable, best-in-class service,” explained NADCA Executive Director John Schulte. “NADCA membership and the VSMR certification mean that a professional is dedicated to providing state-of-the-art service to their customers.”

Edward Frisk, and Jason Erb are now one of roughly 250 VSMR-certified professionals in the world.

HVAC system cleaning is the process by which heating, air conditioning, and ventilation systems are cleaned to remove excessive accumulations of dust, debris, and biological contaminants. Ventilation system mold remediation specifically addresses cleaning and removing biological contaminants within an HVAC system. With heightened public awareness of the dangers of indoor air pollution and the need for home energy efficiency, the demand for professional HVAC system inspection and cleaning has increased dramatically. The NADCA Certification Program helps to ensure that members of the association possess the required knowledge and expertise to perform these services in a competent and professional manner.

NADCA recommends that homeowners and building managers have their HVAC systems inspected annually and cleaned as needed. For more information regarding the benefits of professionally performed HVAC inspection and maintenance, contact Edward Frisk, and Jason Erb of Ductworks, Inc.

About Ductworks, Your Air Duct Cleaning Expert

Ductworks, Inc. “Your Air Duct Cleaning Expert” is a Denver-based company founded in 1990 to improve indoor air quality for homes and businesses. Their patented system of scraping and vacuuming is the most effective process for air duct cleaning. They have more technicians certified by the NADCA than any company in Colorado and provide customers with before and after photos to insure top quality performance.

About NADCA:

NADCA – The HVAC Inspection, Maintenance and Restoration Association was formed in 1989 as the National Air Duct Cleaners Association, and has since expanded its mission to become a trusted advocate for consumers and the industry on environmental and health issues surrounding heating, ventilation and air conditioning (HVAC) systems. NADCA was the first organization to develop industry-standard best practices and its standard for “Assessment, Cleaning & Restoration of HVAC Systems” is in use in more than 30 countries worldwide as a best practice and/or basis for national law. NADCA has more than 1,000 corporate members and more than 1,500 individuals certified as Air System Cleaning Specialists, Ventilation Inspectors or Ventilation System Mold Remediators. For more information or to find a NADCA-certified contractor near you, visit www.NADCA.com.

NADCA Energy Research Study

For decades the National Air Duct Cleaners Association (NADCA), has been educating consumers on the process and benefits of air duct cleaning. Currently there is research study underway to measure the correlation between energy pressure drop and energy savings.

NADCA Energy Research Study

In February 2008, NADCA entered into a partnership with the Colorado University to conduct a research project that will provide members with a tool for estimating the energy savings associated with HVAC cleaning and restoration projects. The research project was also commissioned to develop a field-testing protocol for NADCA members that will facilitate collection of data to provide broader support for linking HVAC cleaning and restoration to energy savings.

Current Findings and Test Results

NADCA presented the current results of the test at the 2010 Annual Meeting.  Comparisons were made by testing air flow rates when the filter, furnace, and evaporative air conditioner coil were fouled and again when the components were clean.

It was found that a dirty filter increased the filter pressure drop, system pressure drop and reduced the air flow of the ventilation system.

Surprisingly, a clean furnace and evaporative air conditioner coil increases initial energy consumption, but lessoned the amount of time that the furnace an air conditioner had to operate to achieve the desired room temperature. Though there was initial higher energy consumption, there was a net gain in overall energy efficiency.

While further data and testing is required, the current the findings show that proper exchange rate and selection of the furnace filter, routine cleaning of the evaporative air conditioner coil, and sealing of air ducts offer the greatest benefits to energy savings.

Further Testing Underway

Currently NADCA is receiving further test results from companies engaged in the assessment, cleaning, and restoration of HVAC systems.  These test results are being sent to the University of Colorado for further interpretation.

Fiberglass Air Duct Liners | A Serious Indoor Air Quality Concern

Most commercial air duct systems are internally lined with fiberglass duct liners.  Deteriorating fiberglass duct liner is a very common cause for indoor air quality complaints and adverse health effects.

Fiberglass Duct Liner

Fiberglass internal duct liner is commonly used in many commercial heating, ventilation, and air conditioning (HVAC) system.  Fiberglass duct liner provides sound attenuation by dampening noise from HVAC equipment, and sound from adjacent office spaces.  Fiberglass duct liner provides thermal insulation for air ducts, preventing the air ducts from losing expensive conditioned air.

Fiberglass Duct Liner Deterioration

Over time internal fiberglass duct liner is exposed to varying degrees of air turbulence, temperature and humidity.  These environmental changes take its toll on the duct liner, breaking down its primary seal.

The primary seal is a black gritty coating on the surface of the duct liner which locks down the fiberglass fibers.  Deteriorated primary coating migrates through the ventilation system depositing within HVAC components and eventually entering the indoor air.

After the primary seal has fully deteriorated, it allows raw fiberglass fibers to be exposed to the airstream.  Turbulent airstreams wick the raw fiberglass fibers through the ventilation system, creating additional deposits within HVAC components and exposing building occupants to raw fiberglass fibers.

Health Effects of Fiber Glass Fibers

Health effects from exposure to fiberglass can be different depending on the fiber size and type of exposure.  Fiberglass, at a minimum, is an acute physical irritant to the skin, eyes, and upper respiratory tract.

  • While no long-term health effects should occur from touching fiberglass. Rashes can appear when the fibers become embedded in the outer layer of the skin.
  • Eyes may become red and irritated after exposure to fiberglass as occupants touch horizontal surfaces with deposits of fiberglass fibers, and rub their eyes.
  • Soreness in the nose and throat can result when fibers are inhaled. Asthma and bronchitis can be aggravated by exposure to fiberglass.
  • Temporary stomach irritation may occur if fibers are swallowed.

How Can Fiberglass Air Ducts Be Repaired?

If caught in the early stages of deterioration the internal fiberglass duct liner can be repaired.  Fiberglass duct liner can be resurfaced with an encapsulate specifically designed for HVAC systems.   Initially a commercial air duct cleaning needs to be performed to remove the foreign debris from the air duct surface to ensure for a proper bond.  After the air duct system is cleaned, the encapsulate is applied to the air duct surface locking down the fiberglass fibers.

If the internal fiberglass lining to too deteriorated, the lining must be removed and replaced.  If the damage is localized,  new internal internal insulation can be installed within the ducting.  If the damage is extensive, consider removing the damaged insulation and wrapping the air ducts with an external fiberglass insulation.

Pigeons Cause Devastating Indoor Air Quality and HVAC Problems

Pigeon problems have devastating effects on the heating and cooling components and indoor air quality of a commercial facility.  Pigeon problems affect employees, maintenance personnel and potentially customers.

HVAC Systems Make Perfect Pigeon Coups

Unfortunately, rooftop heating and cooling units are a perfect place for pigeons to nest.  To seek shelter from the elements, pigeons typically enter air handler units through the fresh air intakes and build their nests within the HVAC unit.  A single pair of pigeons can generate up to 18 new pigeons per year.  Once a nest is established, pigeons are extremely territorial.

Indoor Air Quality

An HVAC system distributes the air throughout a facility.  The bacteria, fungi and parasites that live and grow in pigeon droppings can carry and transmit any of 60 known diseases.  Exposure to pigeon feces and other organic matter such as feathers carcasses and nesting material from the HVAC system may pose a considerable health threat to people who come in contact with them or inhale the airborne particles from them.  Every precaution should be taken to ensure that building occupants and maintenance personnel are protected from pigeon feces.

Damage to HVAC Systems

As pigeons live in the air handler units they peck through filter material allowing unfiltered air and pigeon contaminants to freely enter the ventilation system.  There are numerous damaging effects to an HVAC system.

  • Filter banks: Pigeons peck though filter banks allowing for unfiltered air and pigeon contaminants to be drawn into HVAC components and supply air ducts.
  • Fan Blower: Pigeon debris builds within the fan blades decreasing airflow.
  • Air conditioner coils: Pigeon debris compacts within air conditioner coils and clogs the drain pan.
  • Insulation: Pigeons peck at insulation to create nesting material allowing for raw fiberglass fibers to enter the airstream.

How Do You Correct Pigeon Problems?


Hire a professional wildlife service or animal control contractor to relocate existing pigeons, and install devices to prevent future intrusions.  Have the pigeon debris removed by a professional air duct cleaning contractor.  Be sure to have the air duct cleaning contractor inspect the supply air ducts downstream of the HVAC unit.

Smoke and Fire Damaged Air Ducts

An air duct system is very efficient at spreading smoke.  When a fire occurs, the entire HVAC system will be contaminated, to a lesser or greater degree.  It is likely that the air duct system will distribute smoke damage well beyond the area of the fire.

Smoke Damage from an Active Air Duct System

Unfortunately, a forced air ventilation system is rather effective at spreading smoke damage.  Smoke is drawn into return air vents, through the furnace components, and distributed throughout the home or building through the supply air ducts.  If the HVAC system was operating at the time of fire, the return air side will be the most contaminated.

Passive Air Duct Smoke Damage

Even if the heating and ventilation system is not in use, there is a natural or passive air movement throughout the ventilation system.  If the air duct system wan not in operation during the fire, the return and supply air ducts closest to the fire will be the most contaminated.

Absorption of Odors

Smoke is naturally attracted to metal surfaces and is corrosive in nature.  As the smoke enters the air ducts it will cling to the steel, and will absorb into the debris within the air duct system.  A ventilation system has to be thoroughly cleaned in order to remove smoke damage.

Odor Oxidizer

After the ventilation system has been cleaned, an odor oxidizer is applied within the air ducts.  An odor oxidizer naturally breaks downs the odor causing chemicals of the smoke damage.


In some instances of extreme smoke damage, air ducts will need to be encapsulated to remediate the smoke damage.  After the air ducts are cleaned, an encapsulates approved for use within HVAC systems is applied uniformly throughout the ventilation system.