Creosote Levels and Identification

Why this matters

Creosote is the leading cause of chimney fires. CSIA classifies creosote into three stages, each with different fire risk and remediation requirements. A chimney sweep should recognize the stages, communicate the risk to the customer, and remediate appropriately. Failure to address creosote is failure to protect the customer's home.

What creosote is

Creosote is the buildup of unburned fuel particles in the chimney:

• Combustion is incomplete (some fuel doesn't fully burn)
• Smoke + tar particles condense on the cooler chimney walls
• Over time, creosote accumulates
• When ignited (chimney fire), creosote burns very hot
• Severe chimney fires can cause structural damage AND spread to the home

Stage 1 - Soot (Light Creosote)

This is the typical buildup after a season of fireplace use. Customer's annual sweep removes it.

Stage 2 - Glaze / Tar (Moderate Creosote)

Stage 2 indicates:

• Customer using slow-burning fires (low temperature)
• Wet / unseasoned wood
• Inadequate chimney draft
• Significant accumulation of partially-burned fuel

Removal:

• Power-rotating chimney brushes (Schaefer / Sooteater)
• Chemical creosote remover (applied + brushed)
• Multiple passes
• Sometimes manual scraping (specialty tool)

Stage 3 - Glaze (Severe Creosote)

Stage 3 indicates:

• Years of accumulated creosote without proper cleaning
• Severely restricted draft
• Significant fire risk

Removal:

• May require chemical treatment (potassium hydroxide-based)
• Manual rotary tools
• Sometimes ONLY removable by liner replacement
• The customer's heating system has been operating dangerously

When Stage 3 is found, the customer should NOT use the system until remediated.

Identification

Visual identification during inspection:

Camera / video inspection allows the most accurate assessment of stage progression. Level 2 inspection is essential for finding Stage 2 or Stage 3.

Health and safety

Creosote is:

• Combustible (combustion = chimney fire)
• Mildly toxic on contact (can cause skin irritation)
• More toxic when burned (combustion products)
• Heavy buildup creates a serious fire hazard

For technician safety:

• Skin contact: wash with soap + water
• Respiratory: dust mask when cleaning Stage 2 / 3
• Eye protection from particles

Customer education

For creosote concerns:

1. "What you're burning + how you're burning it affects creosote"
2. "Dry, seasoned wood is the best fuel"
3. "Wet wood produces significantly more creosote"
4. "Slow, low-temperature fires produce more creosote"
5. "Hot, complete burning produces less"

Educate the customer on prevention.

What burns produces less creosote

Wood selection

For lowest creosote:

The customer's wood selection significantly affects creosote production.

Wood storage

Seasoning requirements:

• 1 year minimum for hardwood
• Stored off the ground
• Covered top, open sides
• Sunny / dry location
• Air circulation

Customer should buy wood the year before use.

Annual cleaning frequency

NFPA 211 + CSIA recommendations:

• Annual cleaning for all active fireplaces
• Quarterly cleaning for fireplaces used daily during heating season
• Cleaning when 1/8 inch creosote accumulates (industry rule of thumb)

Standard residential customers should have annual service minimum.

When to clean immediately

If observed:

• Stage 2 or Stage 3 creosote
• Significant soot pile in the fireplace
• Smoke entering the room
• Strong odor of creosote
• Customer reports unusual smoke patterns

These warrant immediate cleaning + investigation.

Treatment options

Customer-side remediation:

1. Cleaning logs (chemical compounds in log form): some effectiveness for light creosote; the manufacturer claims vary; CSIA doesn't endorse them as substitute for professional cleaning
2. Powdered creosote remover (sprinkled on the fire): similar concerns
3. Professional cleaning: the only reliable approach

Professional methods:

Documentation

For each cleaning:

1. Before photos / video
2. Stage of creosote identified
3. Cleaning method
4. After photos / video
5. Customer signature

Camera footage of before/after is a powerful customer communication tool.

Chimney fire response

If a chimney fire occurs:

1. Call 911 immediately (fire department)
2. Close the damper (limits oxygen)
3. Customer leaves the home
4. Do not attempt to fight the fire yourself
5. After the fire, mandatory Level 3 inspection

Chimney fires:

• Can sound like a freight train (creosote burning at high temperature)
• May discharge embers from the top of the chimney (catch the roof)
• Can damage the chimney structure significantly
• Don't always indicate the chimney is unsafe; may be repairable

References

• NFPA 211 (Standard for Chimneys, Fireplaces, Vents)
• CSIA (Chimney Safety Institute of America) creosote classification
• NFI (National Fireplace Institute)
• USDA Forest Service wood burning recommendations
• EPA solid fuel combustion guidelines
• Manuall internal: Chimney Sweep Service SOP, NFPA 211 Inspection Levels, Smoke Draft Problems