.png)
Smoke Testing a Subfloor: How We Found Hidden Air Leaks Contributing to Mould Issues in a Burwood Home
- Michael Nguyen
- 16 hours ago
- 4 min read
By Michael Nguyen
Smoke Testing a Subfloor: How We Found Hidden Air Leaks Contributing to Mould Issues in a Burwood Home
When homeowners discover recurring mould growth, musty odours, or poor indoor air quality, the source is not always visible. In many Sydney homes, particularly older properties with suspended timber floors, the problem may actually originate from the subfloor.
Recently, our team conducted a specialised smoke test at a residential property in Burwood, Sydney, to investigate whether air from the subfloor cavity was entering the living areas of the home.
The results revealed several hidden pathways that could potentially allow moisture, odours, and airborne mould spores to migrate from the subfloor into occupied spaces.
Here is a video from our YouTube channel of the smoke test process
Why We Use Smoke Testing During Mould Investigations
Smoke testing is a powerful building diagnostic tool that helps identify unwanted airflow pathways between different parts of a building.
During the test, a non-toxic theatrical smoke machine is used to introduce visible smoke into the subfloor cavity. The technician then inspects the home for any signs of smoke entering through:
- Floor penetrations
- Plumbing penetrations
- Electrical penetrations
- Gaps around skirting boards
- Cracks in flooring systems
- Wall cavities
- Service ducts
Where smoke can travel, air can travel.
This means that if a damp subfloor contains elevated mould levels, contaminated air may also be entering the occupied areas of the home.
The Burwood Property Investigation
The owners of this Burwood property had reported:
- Persistent musty odours
- Recurring mould growth
- Concerns about indoor air quality
- Elevated moisture levels beneath the home
During our inspection, we identified signs of moisture accumulation within the subfloor. To determine whether air from this area was communicating with the living spaces above, we performed a smoke test.
Once smoke was introduced into the subfloor cavity, several leakage pathways became immediately visible inside the house.
This confirmed that air movement was occurring between the subfloor and occupied areas.
Why Air Leakage Matters
Many people assume mould problems are only caused by visible mould growth on walls and ceilings.
However, the movement of air is often an overlooked factor.
When air moves from a damp subfloor into living areas, it can transport:
- Mould spores
- Fungal fragments
- Microbial volatile organic compounds (MVOCs)
- Musty odours
- Excess moisture
Over time, this can contribute to indoor air quality issues and create conditions that support further mould growth.
The Building Science Behind Subfloor Air Movement
Air naturally moves from areas of higher pressure to lower pressure.
Common household activities such as:
- Running exhaust fans
- Using range hoods
- Operating clothes dryers
- Reverse-cycle air conditioning systems
can create pressure differences within a home.
These pressure differences can draw air from a damp subfloor through hidden gaps and openings.
In homes with poor subfloor ventilation, moisture accumulation can increase the likelihood of mould development beneath the floor structure.
Common Signs of Subfloor-Related Mould Problems
You may benefit from a professional subfloor assessment if you notice:
Persistent Musty Smells
Odours that return despite cleaning or mould treatment may indicate an underlying source beneath the home.
Mould Returning After Cleaning
Repeated mould growth often suggests an unresolved moisture source.
Damp Indoor Air
A humid or stale feeling indoors may be linked to hidden moisture accumulation.
Respiratory Symptoms
Some occupants report increased respiratory irritation when indoor air quality is affected by elevated mould levels.
Our Scientific Approach to Mould Investigations
At AAA Mould Removal, we focus on identifying the source of mould issues rather than simply treating visible growth.
Our investigations may include:
- Moisture mapping
- Thermal imaging
- Subfloor inspections
- Air quality assessments
- Particle monitoring
- Smoke testing
- Mould sampling where appropriate
This evidence-based approach helps ensure remediation efforts target the underlying cause of the problem.
The Importance of Source Identification
The AS-IICRC S520 Standard for Professional Mould Remediation emphasises the importance of identifying and correcting moisture and contamination sources before remediation begins.
Without addressing the underlying cause, mould is likely to return.
Smoke testing can provide valuable information about hidden airflow pathways that may otherwise go undetected.
Need a Mould Inspection in Sydney?
If you're experiencing recurring mould growth, musty odours, or concerns about indoor air quality, a professional investigation can help identify the root cause.
AAA Mould Removal provides scientific mould inspections, moisture investigations, and remediation services throughout Sydney.
Book an inspection today:
---
Frequently Asked Questions
What is smoke testing?
Smoke testing uses a non-toxic visible smoke to identify air leakage pathways within a building. It is commonly used to investigate indoor air quality issues and building envelope defects.
Can mould spores travel from the subfloor into the house?
Yes. If air pathways exist between the subfloor and living areas, airborne mould spores and other contaminants can potentially be transported into occupied spaces.
Is smoke testing safe?
When performed by trained professionals using appropriate smoke-generating equipment, smoke testing is generally considered safe for building diagnostic purposes.
Do all mould investigations require smoke testing?
No. Smoke testing is one of several diagnostic tools used when investigating moisture, air leakage, and indoor air quality concerns.
Do you service Burwood and the Inner West?
Yes. AAA Mould Removal provides mould inspections, mould testing, remediation, and structural drying services throughout Burwood, the Inner West, and greater Sydney.
---
About the Author
Michael Nguyen is the founder of AAA Mould Removal and a leading expert in mould remediation and building science.
He holds IICRC certifications in Water Damage Restoration, Applied Microbial Remediation, and Applied Structural Drying. Michael studied Microbiology at RMIT University, is a licensed builder and carpenter with a Diploma in Building & Construction, and is currently completing a double Bachelor's degree in Medical Science and Environmental Science at Macquarie University.
He specialises in residential and commercial mould removal, black mould treatment, indoor air quality investigations, and water damage restoration throughout Sydney.
Contact AAA Mould Removal today for a comprehensive mould inspection and remediation assessment.
Comments