Thermal fogging is a deodorization technique used mainly after fire and smoke damage. It uses heat to turn a deodorizing solution into a fine fog that penetrates the same places smoke reached. When used correctly, after cleaning, it can be very effective. This guide explains how it works and where it fits.
How thermal fogging works
A thermal fogger heats a specially formulated deodorizing solution until it vaporizes, producing a dense fog of very fine particles. Because heated smoke travels into cracks, crevices, wall cavities and porous materials during a fire, a heated fog with very fine particles can follow the same paths and reach odor molecules that surface cleaning can't.
The deodorant in the fog pairs with or neutralizes odor molecules, depending on the product's chemistry.
When it's used
- Fire and smoke damage, especially in structures and contents where smoke penetrated deeply
- Vehicle smoke odor in some cases
- Some other odors, depending on the product, after source removal
Thermal fogging is less suited to odors from saturated organic materials such as decomposition fluids or urine in subfloors, where removal and enzymatic treatment are the primary methods.
Where it fits in the process
Thermal fogging is one step in fire and smoke restoration:
- Remove debris and unsalvageable materials.
- Clean soot and smoke residue from surfaces, contents and HVAC systems.
- Deodorize with thermal fogging, hydroxyl treatment, ozone in unoccupied spaces, or a combination.
- Seal structural materials where needed.
- Restore finishes.
Fogging without cleaning leaves soot and residue behind, and odor returns.
Safety considerations
- Unoccupied space. People and pets must leave during fogging and stay out until the product's re-entry time has passed and the space is ventilated.
- Fire safety. Thermal foggers use heat; operators follow manufacturer instructions, and smoke detectors and fire alarm systems may need to be managed in coordination with building management or the fire alarm company to prevent false alarms.
- Products. Only products formulated for thermal fogging should be used, according to label directions.
- Residue. Some fogging products may leave a light film or scent; operators choose products and quantities to minimize residue.
- Sensitive items. Electronics and valuables may need protection.
Thermal fogging versus other fogging
- ULV (ultra-low-volume) fogging produces droplets without heat and is commonly used for disinfectants or deodorizers on surfaces.
- Thermal fogging produces finer particles with heat, which penetrate more deeply, and is used mainly for smoke odor.
Limits
- It doesn't remove soot or residue.
- It doesn't fix saturated materials.
- It requires vacating the space.
- Results depend on preparation and product choice.
A practical example
After a kitchen fire, crews remove the burned cabinets, clean soot from walls, ceilings and contents throughout the house, and clean the HVAC system. With the house empty, they thermal fog the structure. After the re-entry period and ventilation, a hydroxyl unit runs while contents are returned. Walls are sealed and repainted.
Common mistakes
- Fogging before cleaning soot
- Allowing occupants back too early
- Ignoring the HVAC system
- Using products not labeled for thermal fogging
Contents after a fire
Contents such as clothing, furniture and books often carry smoke odor. Washable textiles can be laundered with smoke odor treatments; others may go to professional cleaning, sometimes with ozone in a dedicated chamber. Hard items are wiped clean. Thermal fogging of the structure is most effective when contents have been removed or cleaned, so they don't re-introduce odor afterward.
Who should perform thermal fogging
Fogging is typically performed by fire and smoke restoration professionals with training on the equipment and products. Because it involves heat and dense fog, it isn't recommended as a do-it-yourself project. Insurance claims for fire damage often include deodorization as part of the restoration scope.
Measuring success
Success is judged by odor, not appearance. After fogging and ventilation, walk through the structure under normal conditions, open closets and cabinets, and run the HVAC system. If odor remains in a specific area, more cleaning or sealing there is usually needed.
Frequently asked questions
Is thermal fogging safe?
When performed by trained operators in an unoccupied space with appropriate products and ventilation, risks are managed.
Will fogging remove smoke stains?
No. Stains must be cleaned or sealed.
How long must we stay out?
Follow the product's re-entry instructions and the operator's guidance, typically including ventilation time.
Does fogging help with decomposition odor?
It may help as a final step, but source removal and enzymatic treatment are the primary methods.
Can fogging set off fire alarms?
Yes, fog can trigger detectors; operators coordinate to prevent false alarms.
Is thermal fogging the same as ozone treatment?
No. Fogging disperses a deodorizing product; ozone uses a gas that oxidizes odor molecules.
Does insurance cover thermal fogging?
It's often part of fire and smoke restoration covered under property policies. Check with your adjuster.
How many fogging treatments are needed?
Often one after thorough cleaning; heavy odors may need a second treatment.
Key takeaways
Thermal fogging uses heat to create a fine deodorizing fog that follows smoke's paths into hard-to-reach places. It's most useful after fire and smoke damage, as a step after cleaning soot and residue. It requires an unoccupied space, careful fire safety and appropriate products.
Sources
This guide is general information. It is not legal, medical, environmental or safety advice. Rules vary by state and locality. For a specific situation, consult the relevant agency or a qualified professional.