Last updated on July 1, 2022

Air ducts are one of the most important parts of your HVAC system. Over time, the air duct gets dirty due to the accumulation of debris, dirt, dust, and requires regular maintenance. 

A place like Australia where the temperature during summer reaches 40 °C, it becomes unbearable to stay without an HVAC system. To identify these significant warning signs of dirty ducts to make sure the smooth working of your AC unit.


If you see a small initial puff of dust come out with the airflow, it is an indication that there is more dust present in the duct that sometimes hinder the smooth airflow.

Usually, air ducts do not emit any noticeable debris or dust when the air starts to flow through the ducts. Visible dust could be due to extremely dirty air registers. However, even by regular cleaning or the air registers, the problem remains, it is most likely due to trapped interior dust instead.


A strange odour is one of the most important signs that there may be debris hiding inside the air ducts of your HVAC system. 

When you notice a foul smell and you’ve checked every possible place in your house and still can not find anything amiss, it’s time you should check the air ducts.

You can test the air ducts by giving a good sniff close to a duct or you hire professional air conditioning experts to look inside the air ducts to check for trapped debris, dirt, dust, mould, or mildew, etc.

Clogged Air Filter

Clogged air filters are the solid indicator that dust and debris have piled up in your HVAC system. Regular cleaning or replacing the air filters can nip the issue in the bud. 

Other Problems That Result From A Clogged Air Filter


Inadequate Amount Of Cooling

Increased Energy Consumption

Frozen Evaporator Coils

Unhealthy Air

Restricted Smooth Airflow


Your air ducts need cleaning when you notice the brown, grey, or black mould or mildew accumulating on or around your air registers.

However, if the mould or mildew is present inside your air ducts, the simple process of vacuuming, sanitizing, and deodorizing is enough to clean the air duct. It can save you from taking apart the entire AC unit to clean the mould out.

Visible debris

If after taking off the air registers, you notice dust inside the duct, it means your air ducts have become clogged and need maintenance.

One of the best ways to remove the dust and debris is with a brush or clean cloth. If the debris arises more often, it is time to call pros for professional air duct cleaning.

Dirty A/c Coil & Other Interior Parts

If your A/C’s coil and other interior parts are jammed with mould, mildew, dust, debris, and other detritus, it indicates that dust trapped in the HVAC system now has begun to move through the air ducts to affect the other peripheral system components.

The dirty A/C’s coil requires thorough cleaning and if the dust quickly returns, you need to clean the entire system to solve the issue once and for all.

Uneven Airflow

Uneven airflow occurs when some air registers allow smooth airflow while other registers are not providing a clear passage of airflow. 

It may be caused by various reasons other than dirty, blocked, or leaky ducts including

Obstructed Condenser Unit

Dirty Coils

Clogged Filters

Oversized Ac Unit

Thermostat Issues

Sluggish Fan

Blocked Vents And Registers

Low Refrigerant Levels

Outdated HVAC Design


Cleaning your AC’s air ducts isn’t something that you should attempt on your own. The complex process of duct cleaning requires advanced knowledge of HVAC systems. 

So always rely on professional air conditioning service and repair in Australia. They are equipped with specialised tools and use the most up-to-date methods and processes to give the best results.

Posted onJanuary 23, 2020

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