Smoke Odor Restoration: Ozone, Hydroxyl, and Thermal Fogging

Why Surface Cleaning Is Not Enough

Smoke molecules — volatile organic compounds (VOCs), aldehydes, ketones, and particulate carbon — bond to porous surfaces through adsorption. A thorough surface wash removes soot but leaves VOC odor molecules embedded in:

• Painted drywall (porous gypsum core absorbs VOCs)
• HVAC ductwork and insulation (often requires dedicated duct cleaning + fogging treatment)
• Carpeting and upholstery (if not removed)
• Wood trim, window frames, door jambs
• Drop ceiling tiles (typically removed and discarded — cost-effective vs. deodorization)

Per the IICRC S770 Standard, deodorization must follow complete physical cleaning — applying deodorization technology to surfaces still bearing soot deposits is ineffective and creates additional compounds from chemical reactions between the deodorizer and unremoved smoke residue.

Technology Comparison

Ozone Treatment Protocol

Ozone is the most common commercial smoke odor treatment because it is effective, low equipment cost, and well-understood. However, it requires strict occupancy control.

OSHA/NIOSH ozone limits:

• NIOSH ceiling: 0.1 ppm (never exceed for any duration)
• OSHA PEL: 0.1 ppm (8-hour TWA)
• Active treatment levels inside structure: typically 1–4 ppm for deodorization efficacy

At 1–4 ppm, any person entering the treated space is at immediate risk. BSC protocol must include:

1. Secure perimeter: Lock all entry points; post OZONE TREATMENT IN PROGRESS warning signage at every door (required)
2. Generator sizing: Rule of thumb = 10,000 mg/hr ozone output per 1,000 CF of space (ceiling height matters; 10,000 SF at 9-ft ceilings = 90,000 CF)
3. Distribute units: Multiple smaller generators distributed through space penetrate further than one large unit at entrance
4. Treatment duration: Typically 24–72 hours depending on damage severity; longer treatments required for heavy soot-laden materials
5. Purge cycle: Run exhaust fans or open windows for 2–4 hours after treatment before occupant re-entry; verify ozone levels with electrochemical sensor (must reach <0.05 ppm)
6. Re-entry criteria: Test with meter before allowing occupants back; document reading

Hydroxyl Generator Protocol

Hydroxyl generators are the professional choice for occupied buildings and healthcare environments because they produce no ozone. Slower than ozone treatment (typically 2–4× longer for equivalent odor elimination), but safe for use while building is occupied.

Proper deployment:

• Place units centrally in affected areas — hydroxyl radicals are short-lived and work within a limited radius
• One unit per 1,500–2,000 SF for standard applications; increase unit density for heavy odor
• Run continuously 24/7 during treatment period (typically 3–7 days for moderate smoke damage)
• HVAC can remain running during hydroxyl treatment; actually assists distribution

Client education: Hydroxyl generators work more slowly than ozone. Set client expectations: a property manager accustomed to ozone's 72-hour cycle should understand that hydroxyl may require 5–10 days for equivalent results. The trade-off is zero occupancy disruption.

Thermal Fogging Protocol

Thermal fogging is the most penetrating deodorization method and the industry standard for heavy smoke damage in structural materials. The heated petroleum-based carrier solvent vaporizes to match the behavior of smoke molecules — penetrating into the same spaces where smoke odor is embedded.

Protocol:

1. Remove all people and pets; ensure no ignition sources (fogging solvent is combustible)
2. Close all windows; seal HVAC intake; seal gaps to adjacent occupancies
3. Begin fogging at the far point of the structure, work toward exit
4. Fog into wall cavities, ceiling plenum (remove tiles), ductwork (via access points)
5. Seal building for 1–2 hours after fogging
6. Ventilate for minimum 2–4 hours before re-entry
7. Follow-up with air scrubbers to capture residual particulate

HVAC System Deodorization

HVAC ductwork is a critical and frequently missed smoke odor source. Smoke distributes throughout a building via air handlers — the same system that will continue to circulate residual odor after room treatment if the ductwork is not addressed.

HVAC odor treatment sequence:

1. Lock out HVAC during initial structural fogging
2. Inspect and replace air filters (always — filters trap soot and re-emit odor)
3. Access ductwork via grilles and access panels; visual inspect with mirror and flashlight for soot deposit
4. Clean duct surfaces with HEPA-equipped negative-pressure duct cleaning system (per NADCA ACR 2021 standards)
5. Apply ULV cold fog with water-based deodorant through duct cleaning access ports
6. Replace filters again after treatment

HVAC duct cleaning and deodorization is typically a separate line item in the restoration scope; billing at $0.25–$0.45 per linear foot of duct or $1.00–$2.00 per grille/register treated.

Pricing Smoke Odor Restoration

For full-building commercial smoke restoration, combined deodorization + surface cleaning + HVAC treatment typically totals $2.00–$6.00 per SF of affected area, billed to property/casualty insurance on Xactimate.

Related articles:

• Fire Smoke Restoration Cleaning Guide
• IICRC S770 Fire Smoke Damage Standard
• Restoration Cleaning Xactimate Billing Guide