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Seattle City Light LARRY WEIS, General Manager and CEO
Utility Pole Odors
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What's That Smell from New Utility Poles?

Some Seattle City Light customers have noticed a strange odor coming from recently replaced wood utility poles in their neighborhoods. The source of the odor is the pole treatment compound Seattle City Light uses to protect against insects and decay and extend the useful life of the pole.

This treatment uses carrier oils (typically diesel fuel) to carry preservative chemicals into the wood under pressure. The evaporation of the carrier oil is referred as a method of degassing and leaves the preservative in the wood. The odor dissipates quickly but could fluctuate depending on environmental conditions.

The wood poles are injected with a solution of copper naphthenate dissolved in diesel fuel under pressure. The poles are allowed to dry at the treatment facility before shipment to City Light, but some residual diesel fuel remains. As the residual diesel fuel evaporates, it can cause strong odors, especially on hot days.

Seattle City Light was one of the first utilities in the United States to use poles treated with copper naphthenate. This treatment has proven to be very effective.

Using copper naphthenate is by far the most environmentally preferable option available for treating utility poles. It is the only major wood treatment compound and pesticide for utility poles that is not restricted for use by the Environmental Protection Agency. Other treatments or alternatives such as chromated copper arsenate (CCA) have shown to produce toxic effects to human health and the environment.

Without treatment, utility poles do not last as long, and can be hazardous if in poor condition. Untreated poles add to the utility's operating and maintenance costs and increase the risk of pole failure. Pole failures cause power outages and pose hazards to life safety and the environment.

City Light recognizes the odor can be bothersome for a short period of time. We always are on the lookout for improvements to our wood preservation methods, including ways to reduce odor without reducing the effectiveness of the preservative treatment. We appreciate our customers' understanding and patience while the odors from the recently replaced utility poles evaporate.

Frequently Asked Questions


What is the odor?

It smells like diesel fuel, which is used as a carrier in the copper naphthenate solution Seattle City Light treats wood utility poles with to protect them against insects and decay.

Why use diesel fuel?

The firms we purchase poles from perform a wood preservative treatment process on the poles. That process involves mixing copper napthenate (the active wood preservative ingredient) with diesel fuel. The diesel fuel carries the copper napthenate deeper into the wood for greater preservative protection and longer pole life.

Will the smell ever go away?

Yes, once the diesel fuel in the pole treatment solution dissipates. It's impossible to say exactly how long an odor can last. Warmer weather speeds the release of the diesel fuel.

Are there any health issues associated with the fumes coming off of the pole?

No. It smells unpleasant, but diesel is a relatively benign substance. There is more danger going to the gas station and inhaling gasoline fumes while you fill your car's gas tank.

Why does Seattle City Light use such a smelly material?

Copper naphthenate is the most environmentally preferable option available for protecting wood utility poles against insects and decay. Other treatments can involve chemicals that pose a cancer risk or are restricted by the Environmental Protection Agency.

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