Mould fogging disperses an antimicrobial solution as a fine mist so it reaches cavities, textiles and awkward corners that wiping or spraying cannot cover evenly. It is a supporting step inside a remediation job, used after the moisture source is found and after mouldy material has been physically removed, not a fix on its own. Where it is part of a job arranged through Illawarra Mould Removal, it is carried out by the independent local contractor engaged for that job.
What mould fogging is
A fogging machine breaks the antimicrobial solution into droplets small enough to hang in the air for a while before settling. That is what lets it drift into voids, around obstacles and into fabric weave instead of only coating what is directly in front of the nozzle. The product, its concentration, its contact (dwell) time and the airing-out period before anyone re-enters are set by the manufacturer’s label directions.
The common types:
- Cold or ULV (ultra-low volume) foggers atomise the solution mechanically at room temperature. These are the usual choice indoors and work with water-based products.
- Thermal foggers heat the solution to make the fog. They are less suited to occupied homes because of the heat and the formulations involved.
- Dry fog systems produce a very fine fog intended to leave surfaces barely wet, and are marketed for sensitive contents and electronics.
Misting and fogging are usually the same thing. “Misting” describes the fine mist; “fogging” describes the machine. Watch for one exception: some operators call a hand-held sprayer “misting”. That produces much coarser droplets and is surface spraying, not ULV work. Either way, the word on the quote matters less than what the scope says about the product, where it is applied, the moisture source and what is removed first.
When fogging is used
- As a finishing pass after removal. Once affected plasterboard or insulation is out and the room has been HEPA-vacuumed and cleaned, fogging treats remaining surfaces and air before the space is closed up.
- Hard-to-reach places. Louvre gaps, under built-in wardrobes, ceiling cavities reached through a manhole, heavily textured surfaces.
- Soft furnishings and contents exposed to spores but not the source of growth, such as curtains, some upholstery and stored items, where wiping is impractical.
- Dispersed growth in a cavity. When a subfloor or roof void inspection finds scattered spotting across many timbers rather than one patch, after physical inspection and cleaning.
When fogging is not enough
Fogging does not physically remove mould. Dead growth stays on surfaces until it is cleaned off, and the mist does not reach mould growing deep inside plasterboard, timber or masonry. Most importantly, it does nothing about moisture: NSW Health’s mould factsheet notes mould is likely to return unless the cause is also treated. Our guide to why mould came back after treatment covers the usual reasons.
Fogging is the wrong tool on its own when:
- the moisture source has not been found and fixed
- porous materials are saturated or visibly mouldy and need removing
- the quote says “we’ll fog it” with no inspection, containment or verification
Where fogging sits in a proper job
The IICRC S520 standard sets out the procedures and precautions for professional mould remediation, and our remediation standards guide explains how a job aligned with it is staged. Fogging sits inside that sequence, never in place of it:
| Step | Fogging sold as a shortcut | Fogging inside a proper job |
|---|---|---|
| Moisture source | Skipped or assumed | Found first and named in the scope |
| Containment | Rarely present | Work area sealed before treatment |
| Removal | Mist applied over mouldy material | Unsalvageable material removed first |
| Air and drying | Nothing beyond the mist | Air scrubbing and dehumidifying on larger jobs |
| Verification | None | Moisture readings and a visual check |
A small, contained patch in one ensuite may only need surface cleaning, a fogging pass and a ventilation check. Growth across several rooms, inside wall cavities or after water damage calls for whole-home remediation, with fogging as one stage. Our guide to mould removal versus remediation helps you work out which applies.
Cost and safety
Fogging is normally built into the treatment price for the job it belongs to, because product and time scale with area and access. A flat fogging fee that does not change with the size of the space is worth questioning. The mould removal cost guide explains what drives treatment prices.
During application, people and pets stay out of the treated area, the technician wears protective equipment, and food, aquariums and sensitive items are covered or moved. Smoke alarms may need temporary covers. The product’s safety data sheet and re-entry time should be confirmed at quote stage.
Frequently asked questions
Can fogging alone get rid of mould?
Not reliably, beyond a small, well-defined patch. It treats surfaces and air within reach, but it does not remove mouldy material or fix the moisture feeding the growth.
Is fogging the same as spraying bleach around a room?
No. Fogging uses a purpose-built machine and products labelled for that kind of application; household bleach through a garden sprayer is a different product and a poor substitute on porous materials.
How long do I need to stay out of the house after fogging?
That depends on the product, and the re-entry time on its label directions. Get the exact time from the contractor before treatment starts.
Will fogging get rid of the mould smell?
It can help where the smell comes from surface growth and airborne spores. If the odour comes from mould inside plasterboard, timber or carpet underlay, those materials need removing or physically treating.
Will fogging stop mould coming back?
Only if the moisture source is fixed as well. Fogging treats what is there on the day; it has no effect on future condensation, leaks or poor ventilation.
Find out whether fogging suits your job
Describe the affected area through the quote form and you will get an honest answer on whether it needs simple surface treatment, a scope that includes fogging, or full remediation.