How Mold can be removed from Ducted AC Unit?

Mould growth

Last Updated on June 25, 2023 by

IAQ defined as Indoor air quality has a significant impact on people’s health and their comfort. The mould is a biggest indoor air pollutant. Due to its invisible nature, the released mould spores in the breathing air are inhaled and cause asthma, allergies, and weakened immunity. In air conditioners, this mould is unavoidable as moisture acts as a catalyst for mould and bacteria growth.


Mould is defined as a type of fungi that resides on bio-matter. The mould spores reproduce and distributed itself on air currents in damp and non-ventilated areas.

The moulds vary in their appearance depending on their stages of life and age but most commonly they appear green, black, or white in color. In both environments, outdoor and indoor air mould spores are found and reproduce themselves on moist areas.

What causes mould to grow??

The air humidity, moisture or any type of water source with inadequate supply of sunlight is a triggering factor for mould growth. Any building with the leakage issues such as rising damps, downpipes, blocked gutters, poor ventilation & circulation areas, as well as plumbing leakage provides the best sources of mould reproduction.

The water leakage is not the only reason for mould growth. The temperature variations with high level of humidity produces condensation which is also a contributing factor for their spread.

Mould Growth Parameters in Ducted AC Unit

The moisture is the common triggering factor for all mould growth sites and indoor air conditioner systems are the best location as the unit’s operation involves air circulation outside the building. This outside polluted outer air contains bacterial particles and spores of airborne mould. The mould thrives as it meets the ideal conditions when system turns off and its warm interior temperature the residual condense the moisture within the system and ducting.

Drawbacks of Mould Growth in a Ducted unit

Moulds are the microscopic fungi that can be useful and harmful for humans. They are useful in the sense that they provide cheeses such as camembert and brie with their unique flavor and quality. Some drugs like penicillin is obtained from a mould type.

With an air conditioning system, they spread as airborne particles in the environment and can be gulped through breathing or eating. This creates harmful effects on one’s health. Few of them are briefed below;

Health problems

The mould can prompt a serious reaction to the patients of asthma, allergic sensitivity or any kind of respiratory issues. They can cause irritated eyes, sore throat nasal congestion, coughing, sneezing, and wheezing.

The people with immune deficiency, weakened immunity, or lung diseases are at great risk of increased asthmatic or allergic reactions. Few types of Moulds are the reason of mycotoxins production. They can cause to serious life-threatening diseases like pneumonia.

Mould growth

Moulds have capability to reproduce itself in AC units and spread in the air through its filters and vents. They find alternative places such as in carpets, cupboards, closets, and clothing to settle and grow.

System performance

The presence of moulds in air conditioner can significantly affect their overall performance efficiency and higher running costs, blockage within the ducts and vents of unit drains and results in breakdown.

Detection of Mould Growth in a ducted system

The mould doesn’t appears immediately but can be felt by its bad odor during the operation. The black or grey tone circular marks of mould deposits can be noticed as a well-established mould colony within the inner walls of an AC unit. Even they can spread over walls and ceilings. The noisy system is an indication of internal clogged mechanism due to or mould or dust deposits in it.

How to control mould reproduction

Moulds growth are more problematic to control once they started to establish their colony. The significant prevention methods are briefed below;

Ventilation Access

The damp environments are the most favorable conditions for the moulds growth. By reducing moisture and increasing air circulation the mould growth can be controlled. If ventilation is an issue, then consider purchasing a dehumidifier is a better option.

Reduce the moisture content

As moulds can grow rapidly even within 24 hours, it is highly recommended that wet areas within the building should be dried thoroughly.

Proper care of indoor plants

The indoor plants reduce indoor air pollution and also provides a perfect environment for mould growth. As the excessive water in their storage boxes provide damp places. To avoid this, use natural anti-fungal solutions to control their growth in the soil.

Mould removal from a ducted system

During the maintenance, maximum ventilation and use of filter mask can lower the moulds spore’s exposure. Remove power supply at least thirty minutes before the maintenance.  The maintenance process includes following tasks:

Filter cleaning

The filter cleaning or replacing in a unit, is the best defense against moulds as they mostly deposited on it.

Condenser cleaning

A coil shaped condenser is placed in the outdoor unit and in the direct contact of outside hot air. The condenser should be free from particles like plants residuals, dust and dirt deposits that can affect its functioning and efficiency.

Regular cleaning and inspection

The visible ducts of the ducted system can be cleaned without professional assistance while hidden ducts within ceilings and walls requires thorough maintenance and cleaning with a professional assistance.

Cleaning of an air conditioning system

The bad odor of moulds can be reduced through air fresheners, scented candles, and diffusers. While the internal system cleaning requires warm soap water, a clean piece of cloth to wipe moist surfaces. Then, an aerosol spray or a foam cleaner can be used for cleaning. Finally, apply a clean cloth with a mould inhibitor

Bleach, chemical cleaners and anti-mould sprays must be avoided. As airborne particles of bleach and anti-mould sprays can be inhaled while the chemical cleaners are corrosive in nature and can cause irreversible damage in long-term.

Correct time to seek professional assistance

All types air conditioning systems must have inspected by a trained professional once a year, ideally after winters when temperatures and humidity levels raises.

Read More: How to Keep Bugs from Entering Your A/C?

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Apart from that, if you are interested to know about Preventing Mold Growth then visit our Home Improvement category.