The label is the law. Read your product's label before you mix or apply; the rates here come from the labels listed under Sources.
- Active ingredient
- Copper naphthenate
- Chemical class
- An organometallic compound made by reacting copper salts with naphthenic acids, which usually come from petroleum refining byproducts. It is a dark green liquid that colors the wood, and weathering turns treated wood light brown after several months outdoors.[4]
- Mode of action
- Wood preservative: the copper compound protects wood against wood-destroying fungi and insects (no IRAC or FRAC group)[4][1]
- Signal word
- Copper-Green Wood Preservative: Caution[1]
Color, odor and finishing over it
The label warns that the product will turn wood green and may leave a strong, lingering, unpleasant odor. The green cast fades within a few months in sunlight, and the product isn't intended as a stain.[1]
You can put oil or alkyd stains or paints over it after it has dried thoroughly, about 48 hours, but the green may bleed through lighter colors. For wood you plan to paint, the label calls for one coat; for wood left unfinished, two liberal coats within the hour.[1]
The Forest Service handbook describes weathered copper naphthenate-treated wood as turning light brown after several months, and wood treated with heat as ranging from light brown to chocolate brown.[4]
What EPA's 2007 review found
EPA's September 2007 reregistration decision covered copper and zinc naphthenate together. It found no dermal risks of concern for people applying copper naphthenate products at home, while zinc naphthenate consumer products had to cut their maximum strength to 16% active ingredient.[2]
For children touching treated wood, including incidental hand-to-mouth contact, the review found no risks of concern for wood preservative uses. It had no cancer data for either salt, and it considered copper naphthenate a moderate skin irritant.[2]
To protect bees, the review required either a special honey bee study or a label statement that treated wood shall not be used to build beehives. The current Copper-Green label, stamped in December 2025 as satisfying that decision, carries the beehive statement.[2][1]
Where it fits among wood preservatives
NPIC notes that chromated copper arsenate (CCA) was removed from most residential uses in 2004 and that creosote-treated wood isn't available for use at home. Copper naphthenate comes in oil-based and water-based formulations, and the oil type has been used since the 1940s.[3]
The Forest Service handbook says copper naphthenate isn't a restricted-use pesticide but should be handled as an industrial pesticide. It can be brushed on in solutions of 1% to 2% copper, roughly 10% to 20% copper naphthenate, and the handbook notes ready-to-use solutions sold in gallon containers.[4]
Where it is used
The label recommends it for wood above ground, in ground contact and below ground, wherever wood meets soil or water: window sills, trellises, greenhouse benches, foundations, sills, planter boxes, fence posts, lawn furniture and decks. It is for exterior use only and must not be applied to food or feed contact surfaces.[1]
It comes at full strength, with no thinning or diluting, and the label claims it kills termites and wood-eating insects and prevents rot, decay, fungus and mold. Pressure-treated wood can be treated right away.[1]
The Forest Service's Wood Handbook says copper naphthenate in oil is the preservative most often used for brush or spray treatment, at 1% to 2% elemental copper. It recommends a thorough application on any surface cut after pressure treatment, which leaves a coating that may slowly migrate into the end grain.[4]
Brush-on protection is shallow. The handbook says surface treatments usually penetrate less than 0.1 inch across the grain, and for wood in contact with the ground, service life after such a treatment may be only 1 to 5 years.[4]
EPA's 2007 review says the naphthenate salts are used mostly in industrial and commercial wood preservation, by dip, brush, spray or pressure, and for remedial treatment of in-service utility poles. It says residential use is limited to exterior wood preservation and exterior-use textiles and cordage.[2]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| Copper-Green Wood Preservative[1] | Green Products Co | 66591-1 | 10.0% | ready-to-use liquid | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| Copper-Green Wood Preservative | Exterior wood above ground, in ground contact or below ground (brush coat) | Termites, wood-eating insects, rot and decay, fungus and mold | 150–300 sq ft per gallon per brush coat[1] Label coverage estimate. Applied full strength; several flowing coats if you can't dip. |
| Copper-Green Wood Preservative | Dimensional lumber (dip treatment) | Termites, wood-eating insects, rot and decay, fungus and mold | 5–10 gal per 1,000 board feet per dip treatment[1] Dip at least 3 minutes per inch of thickness; soak fence posts and heavy timbers 12 to 48 hours. |
How to apply it, step by step
1. Protective gear
- The label's signal word is CAUTION: it's harmful if absorbed through skin and irritates the eyes and skin. Wear a long-sleeved shirt, long pants, socks and shoes, and chemical-resistant gloves such as barrier laminate, nitrile rubber, neoprene rubber or Viton.[1]
- Keep it off your skin, out of your eyes and off your clothes. Repeated or prolonged skin contact may cause an allergic reaction in some people. Wash with soap and water after handling and before eating, drinking, chewing gum, using tobacco or using the toilet, and wash contaminated clothing before you wear it again.[1]
2. Before you spray
- It's for exterior use only, with adequate ventilation. The product is combustible because it contains petroleum distillates, so keep it away from heat and open flame, and expect a strong, lingering, unpleasant odor.[1]
- The wood has to be dry and well seasoned. Fence posts and heavy timbers must also be free of bark. Treat wood before it goes into construction; wood that needs protection from subterranean termites must be treated before use.[1]
- Don't apply it to surfaces that will touch food or feed, and don't use treated wood to build beehives.[1]
3. Mixing
- Don't thin or dilute it. It's supplied ready to apply at full strength. Clean brushes and other equipment with paint thinner (mineral spirits).[1]
4. Applying
- Dipping is the label's first choice: dip lumber and wood products for at least 3 minutes per inch of thickness, and soak fence posts and heavy timbers for 12 to 48 hours. If you can't dip, brush on several flowing coats. The label's coverage estimate is 150 to 300 sq ft per gallon by brush, or 5 to 10 gallons per 1,000 board feet when dipping dimensional lumber.[1]
- Use one coat on wood that will be painted. With no finish planned, put on two liberal coats within the hour and cover the ends thoroughly. Don't try to stretch the coverage: the more preservative the wood takes up, the longer it's protected.[1]
- Brush it onto any end or edge you cut or bore after the first treatment. Don't use it in an airless sprayer.[1]
5. After you spray
- Don't install treated pieces until they're thoroughly dry. Oil or alkyd stains and paints can go on after about 48 hours of drying, though the green may bleed through lighter colors.[1]
- The copper gives the wood a green cast that fades within a few months in sunlight. The product isn't meant to be used as a stain.[1]
First aid
- In the eyes: hold the eye open and rinse slowly and gently with water for 15 to 20 minutes, taking out contact lenses after the first 5 minutes, then call a poison control center or doctor. On skin or clothing: take off the contaminated clothing, rinse the skin right away with plenty of water for 15 to 20 minutes, and call a poison control center or doctor.[1]
- If swallowed, call a poison control center or doctor immediately. Don't induce vomiting unless they tell you to, don't give the person any liquid, and give nothing by mouth to an unconscious person. The note to physicians says the petroleum distillates mean vomiting may cause aspiration pneumonia.[1]
- If breathed in, move the person to fresh air. If they aren't breathing, call 911 or an ambulance and then give artificial respiration, and call a poison control center or doctor. Have the container or label with you; the label lists INFOTRAC at (800) 535-5053 for medical questions and emergencies.[1]
Storage, spills and disposal
- Store it only in the original container, kept closed, in a secure, well-ventilated place protected from extreme temperatures, where it can't contaminate water, food or feed.[1]
- For a spill or leak, stop the source, recover the free liquid, spread absorbent and pick it up into containers, then wash the area with detergent and water where that applies.[1]
- Don't reuse the container. Triple rinse it with mineral spirits rather than water, which won't remove the residue: fill it a quarter full, recap, shake for 10 seconds, pour the rinsate into your application equipment or keep it for later use or disposal, drain for 10 seconds after it starts to drip, and repeat twice more. Then recycle it if you can, or puncture it and put it in a sanitary landfill. Leftover product you can't use up by following the label: ask your state pesticide or environmental control agency.[1]
From the safety data sheet
- Green Products Company's safety data sheet for Copper-Green and Copper-Green Brown (EPA Reg. No. 66591-1; prepared in 2013, last revised in November 2018) lists 10 to 15% copper naphthenate carried in 45 to 55% process oil and 30 to 40% mineral spirits. Its OSHA signal word is Warning, and the label hazard text it reproduces is headed WARNING as well.[5]
- The sheet classes the liquid as combustible, with a flash point of 49.4°C (about 121°F), and says vapors in an empty drum can explode if ignited. Keep it away from heat and open flame, use it only with good ventilation, and keep the container closed between uses. It also rates the product Category 1 for both acute and chronic harm to aquatic life.[5]
- Its toxicity data are for the ingredients: a rat oral LD50 of 294 mg/kg for copper naphthenate, and LD50 values above 1,710 mg/kg for mineral spirits (oral in rats, on skin in rabbits). Breathing too much of the mineral-spirits vapor can bring on headache, dizziness, drowsiness, nausea, loss of coordination and even unconsciousness.[5]
- With long or repeated exposure, the sheet says the product may damage the blood, kidneys and nervous system, and that prolonged skin contact can dry and crack the skin or cause dermatitis. Its note to physicians warns that the product contains petroleum distillates and that vomiting may cause aspiration pneumonia.[5]
- For a spill, stop the leak, recover the free liquid, spread an absorbent and pick it up into waste containers, then wash the spot with detergent and water where that's practical. For workplace handling the sheet recommends goggles, neoprene gloves and, in a closed-in area, a NIOSH-approved air mask.[5]
- Store it only in the original container, in a secure, well-ventilated place protected from extreme temperatures and away from strong oxidizing agents. The sheet calls it toxic to aquatic invertebrates, shrimp, and oysters and clams, and says the product is not regulated by the U.S. Department of Transportation.[5]
Safety and environmental hazards
People
The label's signal word is CAUTION: harmful if absorbed through skin, moderately irritating to the eyes and irritating to skin, with possible allergic reactions in some people after prolonged or repeated skin contact. NPIC rates copper naphthenate's short-term toxicity low by mouth, through skin and by inhalation, low for eye irritation and moderate for skin irritation. EPA's 2007 review had no cancer data for the naphthenate salts and found no dermal or inhalation risks of concern for people applying copper naphthenate products at home by brush, roller or low-pressure sprayer.[1][3][2]
Pets
The label lists its precautions as hazards to humans and domestic animals. EPA's 2007 review found no risks of concern when children touch wood treated with naphthenate wood preservatives, including hand-to-mouth contact, and rated the naphthenate salts relatively nontoxic to birds in acute oral and dietary tests.[1][2]
Bees and pollinators
Wood treated with it must not be used to build beehives. EPA's 2007 review said residues in hives could be toxic to bees or end up in honey, and required that prohibition on labels; the Copper-Green label carries it.[2][1]
Fish and water
The label says the product is toxic to fish, aquatic invertebrates and aquatic plants. EPA's 2007 review rated the naphthenate salts moderately toxic to freshwater fish and highly toxic to freshwater invertebrates on an acute basis. NPIC says copper naphthenate isn't highly soluble in water and is only slightly mobile in soil, though it may leach more in acidic soil than in neutral soil.[1][2][3]
Common questions
- Can I treat fence posts that are already in the ground?
- The label's directions are for treating wood before it's installed: fence posts and heavy timbers should be bark-free, dry and well seasoned and soaked for 12 to 48 hours, and wood meant to resist subterranean termites must be treated before use in construction.[1]
- How long until I can paint or stain over it?
- Let it dry thoroughly, about 48 hours, before applying oil or alkyd stains or paints. The green may bleed through lighter colors.[1]
- Can I use it inside the house?
- No. The label says it is for exterior use only, and it must not be applied to surfaces that contact food or feed.[1]
- Can I spray it on?
- Not with an airless sprayer, which the label prohibits. It calls for dipping, or several flowing brush coats when dipping isn't possible.[1]
- Is it safe for a vegetable planter box?
- The label lists planter boxes among its recommended uses but also says it must not be applied to food or feed contact surfaces; it gives no other guidance on growing food in treated wood.[1]
Sources
- U.S. EPA Pesticide Product Label System, “Copper Green Wood Preservative label, EPA Reg. No. 66591-1 (EPA-stamped, Dec. 4, 2025).” www3.epa.gov/pesticides/chem_search/ppls/066591-00001-20251204.pdf (accessed 2026-11-08)
- U.S. EPA, “Reregistration Eligibility Decision for Copper and Zinc Naphthenate Salts (EPA 739-R-07-003, September 2007).” archive.epa.gov/pesticides/reregistration/web/pdf/naphthenate-salts-red.pdf (accessed 2026-11-08)
- National Pesticide Information Center, “Treated Wood Fact Sheet (date reviewed February 2019).” npic.orst.edu/factsheets/treatedwood.html (accessed 2026-11-08)
- USDA Forest Service, Forest Products Laboratory, “Wood Handbook, Chapter 15: Wood Preservatives (G. T. Kirker and S. T. Lebow; General Technical Report FPL-GTR-282).” research.fs.usda.gov/download/treesearch/62259.pdf (accessed 2026-11-08)
- Green Products Company (copy hosted on The Home Depot's product-document site), “COPPER-GREEN & COPPER-GREEN Brown Wood Preservative Safety Data Sheet (Green Products Company, prepared November 1, 2013, last revised November 26, 2018; EPA Reg. No. 66591-1).” images.homedepot-static.com/catalog/pdfImages/38/381d1441-0e56-4421-83dd-dcfe62773ed5.pdf (accessed 2026-11-08)