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What is Level 3 or Glazed Creosote?

creosote in chimneyCreosote is a flammable byproduct of smoke that forms in chimneys when wood burns in the fireplace. You can’t prevent creating some creosote with every fire, but you can keep the amount at a minimum. Professional chimney sweeps categorize creosote by levels:

Level 1: This form of creosote is powdery and easy to remove with a brush during chimney cleaning.

Level 2: At the second level, creosote appears as black flakes that are hard and shiny. The chimney sweep often needs rotary loops or drills to remove this form of creosote.

Level 3: When creosote reaches level 3, it presents a serious danger and is very difficult to remove. This is the thick, tar-like substance known as glazed creosote.

How glazed creosote is formed

When creosote accumulates rapidly inside the flue before previous creosote has been able to dry, the glazed version of this substance forms. It will eventually dry and harden into a highly dense state that easily can ignite and cause a chimney fire.

The reason for a rapid accumulation of creosote is excess smoke, which is produced by low-burning fires or fires fueled by wet, or unseasoned, wood. This is why all hearth and chimney service professionals say to burn only dry wood and not to let weak fires smolder for long periods.

Two dangers of glazed creosote

Glazed creosote can be dangerous in two ways:

1. Chimney fire. Excess creosote is responsible for most chimney fires in the United States each year. When creosote reaches the glazed state, that means there’s enough of the substance in the flue to erupt into devastating fire that could destroy the entire house.

Not all chimney fires are big and obvious, however. Small fires can start and go out on their own, the creosote never fully igniting. These fires can damage the chimney liner and the chimney itself. Signs of a chimney fire include rumbling and ticking sounds coming from the fireplace. If you hear these sounds, call 911 immediately and extinguish the fire in the firebox if safe to do so.

2. Obstruction. Glazed creosote buildup eventually will hamper the drafting of smoke, because the passage in the flue becomes too narrow for smoke to effectively rise through it.

The concern here is that smoke will back up into the home, carrying with it dangerous carbon monoxide, or CO. Invisible and odorless, CO is extremely toxic to humans and animals. For this reason, it’s advisable to always have a working CO monitor in the vicinity of any wood-burning home-heating appliance.

Chimney SweepCleaning creosote

Any level of creosote should be cleaned only by certified, trained technicians. For jobs involving glazed creosote, only professional chimney sweeps have the special acids and equipment required to do the job safely and thoroughly.

If it’s been more than a year since your chimney was properly cleaned, don’t live with the potential danger. Call Hudson Valley Chimney of Poughkeepsie, N.Y. at (845) 471-1071 to schedule a complete chimney inspection and chimney cleaning. We work all year round to keep our customers’ chimneys safe and performing at their best.

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