So we had a roof leak and water was slowly dripping through the exterior wall and drywall. It had been going on for years, but until recently it became noticeably during a heavy rainfall when the water dripped through the drywall.

So my contractor came out and fixed the roof leak and replaced the drywall and insulation. However underneath the drywall my contractor used Copper Green Wood Preservative (contains 10% copper naphthalene), as he claimed would help maintain the wood since it had been getting wet for years.

When he sprayed the Wood Preservative there was a noticeable strong odor, which he said would go away. It has been a three days since he sprayed the internal wall with Wood Preservative.

I researched online that this product is supposed to be only used for exterior use only. Is there any way I can mitigate this issue.

I am thinking about calling my contractor back and having the dry wall removed and re-installing a new one with painting an odor remover primer behind the drywall and adding HVAC tape.

Let me know if it is worth the extra money I put into this? Also just curious if I leave it as it is, is there any concerns I should have like side effects on health issues for using this product indoors?

  • I am also curious to hear thoughts on using this product "under the house." I have in front of me disclosures indicating this work was done some time ago to a house I am interested in, and am wondering about risks of off-gassing > 1 year later.
    – Setjmp
    Oct 7 '15 at 5:17

Your contractor should not have sprayed that stuff inside your wall for a number of reasons:

1) it says on the label that it is for exterior use only.

2) It will not really do any good. That product is similar to many traditional wood preservatives that utilize copper napthenate to treat wood before it is exposed to moisture. Putting it on after the fact is arguably useless. It is commonly used for wood that will be left outside without a protective finish. Pressure-treated lumber is treated with copper napthenate, that's why it is green.

3) The stuff is smelly, and covering it up before it was dry (if that's what he did) will prolong the drying time.

The product "carrier" is mineral spirits (paint thinner); oil-based paints using paint thinner or turpentine as a carrier solvent have been used indoors for a long time. The "danger" to you is likely minimal. The TLV (Threshold Limit Value; which is how much an average worker can be exposed during an 8-hour work day with no respiratory protection and no significant health effect) is 500 PPM (parts per million) for Green Products Co. Copper Green. Without a detection device to measure you can't really assess your exposure level, but opening a window nearby to provide ventilation will significantly reduce the concentration.

You will have to make a "trouble vs. gain" decision on whether to have it ripped out. Opening the wall and providing ventilation to ensure it dries would fix the issue. Once dry, there would be no real reason to further "seal" over it unless irritating odors persist.

Material Safety Data Sheet

  • 2
    Copper napthenate, think mothballs... The long term stink is from it slowly evaporating and leaving the copper behind. Dec 13 '14 at 3:27

I had a contractor place it over a wood that had been leaked on. He stripped the wet part off and painted a large area with copper green. It was near my bedroom and I couldn't stand the smell. There days after he applied it I ended up in the ER with a severe lung infection called pleurisy. I had to have them rip out all the drywall they applied it to and put in new. They painted it with a sealant. Some people are more sensitive than others. My recommendation is NEVER use it inside!

  • I'll second that. Before someone says "but it doesn't bother me" (after brief exposure), think about people who are allergic to peanuts. The fact that most of us get nutrition from eating peanut butter doesn't keep it from killing those who are allergic to peanuts. Jul 30 '18 at 13:55

I have the same problem. I called the company and they asked me to do the following. But you can confirm.

  1. clean up the area where copper green was applied using paint thinner or acetone or dawn dish soap. This may help remove the oil.
  2. Use kilz primer max. Prime wood with that.

In future use greens clear as it is good for interior use and its odorless.


I used it inside but during temperatures when I could have the windows open and attic fan running for 2 or 3 days solid. Especially when applying it you want serious ventilation in that area. The smell dropped significantly after 72 hours of drying, but the odor still lingered a week later. Once the copper green was dry to the touch, i brushed over it with minwax oil based poly. That had a huge impact on masking the lingering odor. After two days of the poly drying, the smell was completely gone. This process is not something you can do in a few days and slap new drywall up. You need to open up the affected area, let it dry out, apply the copper green and let it fully dry, apply a sealant and let it dry, then you're ready to put things back together.


Ideally, Copper Napthenate is for exterior use, while Borates for interior use. Borates are colorless, odorless and non-toxic, but being water soluble, unsuitable for exterior use, or for exterior wall studs where roof leaks may cause leaching of the material when wet. Other than the smell that dissipates over time, the copper napthenate will be fine inside the wall.

Borates and Copper Napthenate can be used on previously damaged wood, at which point further damage is prevented.


Just a thought on preserving the with copper green. Apply and let it stay outdoor for a while til the smell drops.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how better to contribute here. Jun 19 '19 at 10:15
  • 1
    Not necessarily a good idea. Just because the smell is no longer detectable doesn't mean that toxins are no longer present.
    – Chenmunka
    Jun 19 '19 at 10:20
  1. A potential neutralization of the surface wood and other materials including plaster and drywall, is using Dawn Ultra dishwashing soap, which will remove surface oil. a. I recommend using it as a hot water solution, such as above 100F.
    b. The issue then becomes, most people do not know how to mitigate porous and sealed wood correctly. Meaning, they wet wipe or spray the wood and wipe it is with the same wipe they used for the last 10 square feet or more. c. Ideally, materials should remain wet for 10 minutes, where the surfactants in Dawn Ultra absorb into the pores of the material, where they can be more easily wiped. d. Wiping (cleaning off Dawn Ultra solution) should be done with commercial grade towelettes (diapers) that are 2-square feet in size, where the “folding of the towel that provides a clean towel area” should cover 2-square feet or maybe larger depending on the debris on the towel. e. Note: wiping the interior surfaces will allow the towel to cover 3 to 5 square feet, where in a crawlspace, wiping on potentially dirty raw wood may result in turning the clean side every square foot.
  2. Once the above is complete or as a potential alternative; I have had success removing other porous contaminates (e.g., smoke embedded in wood from a fire), through vapor steam cleaning. A commercial vapor steam cleaning machine uses 300F plus temperatures. Once vapor steam cleaning is applied the residue can be put into a spray foam and vacuumed off.
  3. The procedures I am recommending are environmentally green, and they are not a sealer or a coverup.
  4. You want to avoid sealing or encapsulating copper green naphthenate and increasing the complications of neutralization. Patrick Moffett, general contractor, environmental/industrial hygienist.
  • 1
    Welcome to Home Improvement. It appears you may have missed points 1 & 2. Please feel free to edit your post to put them in, or to fix up the numbering so you start at #1 so others aren't confused. Also, there's no need to "sign" your posts. Please put your credentials in your profile. If you'll take the tour and browse the help center these and other differences between this Q&A forum and other general discussion boards will become obvious.
    – FreeMan
    Mar 10 '21 at 12:38

Copper II once dry is like pressure treated lumber with Copper II on it and can be used indoors as long as the area is well ventilated.

You are not going to drink Copper II and neither are you going to put your tongue over fresh pressure treated lumber.

How do you think they apply copper II in the lumber mills to the lumber indoors? They ventilate the area and the workers wear safety gear.

People are going crazy and never use common sense these days.

  • "as long as the area is well ventilated." Speaking of common sense, why is ventilation needed - something toxic (napthalene) is coming out of the treated wood, yes? I am curious about what you would consider to be a safe level of long-term exposure, especially for children or adults with allergies or asthma, and how would you determine that level? Would it be based on your reaction to the chemicals or their reaction to the chemicals? Jul 30 '18 at 14:10

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