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Preservative-Treated Wood 

and Alternative Products 

in the Forest Service 

Un ted States 

Department of 

Agricu ture 

Forest Serv ce 

Techno ogy & 

Deve opment 

Program 

7300 Facilities

7700 Transportat on i

April 2006 

0677-2809-MTDC 
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Civil Ri i

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James “Scott” Groenier 

Pro ect Leader

Stan Lebow 

Research Scientist, Forest Products Laboratory

USDA Forest Service 

Technology and Development Program 

Missoula, MT 

TE42G01—Technical Services ECAP 

April 2006 

Preservat ve-Treated Wood 

and A ternat ve Products 

n the Forest Serv ce 

The U.S. Department of Agr cu ture (USDA) proh ts scr minat on al ts 

programs and act es on the bas s of race, co or, nat ona orig n, age, d sab ty, 

and where app cable, sex, mar ta status, fam status, parenta status, rel on, 

sexua or entat on, genetic nformat on, po ca be efs, repr sal, or because a or 

part of an ind dua ’s ncome s derived from any pub c ass stance program. (Not 

proh ted bases app y to a programs.) Persons w th d sab es who requ re 

ternat ve means for commun cat on of program nformat on (Bra e, arge pr nt, 

aud otape, etc.) shou d contact USDA’s TARGET Center at (202) 720-2600 (vo ce 

and TDD). To fi e a comp nt of d scr nat on, write to USDA, D rector, Office of 

ghts, 1400 Independence Avenue, S.W., Wash ngton, D.C. 20250-9410, or 

ca (800) 795-3272 (vo ce) or (202) 720-6382 (TDD). USDA s an equa opportun ty 

prov der and emp oyer.

Cover photo—An elevated walkway 

in Palfrey’s Glen State Natural Area 

near Merrimac, WI.
T

A

he following information was obtained from the U.S.

Department of Agriculture (USDA) Forest Service 

Forest Products Laboratory, National Wood in 

Transportation Program; American Wood-Preservers’ 

Association; Western Wood Preservers Institute; and 

the U.S. Environmental Protection Agency. The authors 

thank these organizations for their help in providing 

information for this report.

cknowledgments 

ii
Liability and Nonendorsement Disclaimers 

Neither the United States Government nor any of its 

employees, makes any warranty, express or implied,

including the warranties of merchantability and 

fitness for a particular purpose, or assumes any legal 

liability or responsibility for the accuracy, completeness,

or usefulness of any information, apparatus, product, or

process disclosed, or represents that its use would not 

infringe privately owned rights.

Reference herein to any specific commercial products, 

process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or 

imply its endorsement, recommendation, or favoring by

the United States Government. The views and opinions 

of authors expressed herein do not necessarily state or 

reflect those of the United States Government, and shall

not be used for advertising or product endorsement 

purposes.

This publication does not contain recommendations for

the use of pesticides, nor does it imply that the uses 

discussed here have been registered. All uses of pesticides

must be registered by appropriate State and/or Federal 

agencies before they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife—

if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended 

practices for the disposal of surplus pesticides and 

pesticide containers.

iii
Contents 

Introduction _________________________________ 1

Types of Wood Preservatives __________________ 2

Oil-Type Preservatives ____________________________ 3

Creosote ____________________________________ 3

Pentachlorophenol ___________________________ 4 

Copper Naphthenate__________________________ 5

Oxine Copper (Copper-8-Quinolinolate) _________ 5

IPBC and Insecticides _________________________ 6

Waterborne Preservatives _________________________ 7

Chromated Copper Arsenate (CCA) _____________ 7

Ammoniacal Copper Zinc Arsenate (ACZA)_______ 8

Alkaline Copper Quaternary (ACQ) Compounds __ 8

Copper Azoles (CBA-A and CA-B) _______________ 9

Borates ____________________________________ 10

Other Waterborne Preservatives _______________ 11

Preservatives That Are No Longer Available 

 Commercially _________________________________ 11

Ammoniacal Copper Arsenate (ACA) ___________ 11

Acid Copper Chromate (ACC) _________________ 11

Ammoniacal Copper Citrate (CC) ______________ 12

Copper Dimethyldithiocarbamate (CDDC) ______ 12

Summary of Preservative Properties __________ 13

Treatment Processes _________________________ 14

Pressure Processes ______________________________ 14

Full-Cell Processes___________________________ 14

Modified Full-Cell Processes __________________ 14

Empty-Cell Processes ________________________ 14

Treating Pressures and Preservative Temperatures _ 15

Penetration and Retention ____________________ 15

Nonpressure Processes___________________________ 16

Surface Applications _________________________ 16

Cold Soaking and Steeping____________________ 17

Diffusion Processes __________________________ 17

Vacuum Processes ___________________________ 18

Other Nonpressure Processes _________________ 18

Alternatives to Treated Wood _________________ 19

Leaching and Its Effects on the Environment __ 21

Recommended Guidelines____________________ 24

Selecting a Wood Preservative_____________________ 24

Wood Species _______________________________ 24

Type of Structures ___________________________ 24

Ecosystem Sensitivities _______________________ 25

Purchasing Treated Wood Products ________________ 25

Treatments _________________________________ 26

Best Management Practices ___________________ 28

Use of a Treated Wood Product____________________ 30

Site Selection _______________________________ 30

Phaseout of CCA for Residential Uses ___________ 30

Allowable Uses of CCA-Treated Wood for 

 Forest Service Projects ______________________ 31

Construction, Handling, and Field Treatment ________ 32

Disposing of Treated Wood _______________________ 33

Material Safety Data Sheets ___________________ 34

Corrosiveness of Treatments _________________ 35

Web Sites____________________________________ 36

Other Sources of Information ________________ 37

References __________________________________ 38

Appendix A—EPA-Approved Consumer 

 Information Sheets for Wood Pressure 

 Treated With Pentachlorophenol or Creosote______ 40

Appendix B—Consumer Safety Information 

 Sheet: Inorganic Arsenical Pressure-Treated 

 Wood (Including CCA, ACA, and ACZA)____________ 44

iv
Introduction 

This report is an update to Selection and Use of 

Preservative-Treated Wood in Forest Service 

Recreational Structures (9523–1203–SDTDC, LeBow

and Makel 1995). One of the main types of wood preservatives, chromated copper arsenate (CCA) has been 

voluntarily phased out for most uses around residential 

areas and other areas where human contact with preservative-treated wood is common. This updated report will

discuss different preservative treatments to replace CCA

and alternative materials that can be used instead of 

preservative-treated wood, such as decay-resistant heartwoods, plastic wood, and vinyl.

Wood is treated with preservatives to protect it from 

wood-destroying fungi and insects. Treating wood with

preservative chemicals can increase the service life of 

wood by a factor of five times or more. Wood treated 

with commonly used wood preservatives can last 40 

years or more in service. Preservative-treated wood 

(figure 1) is an economical, durable, and aesthetically 

pleasing building material and is a natural choice for 

many construction projects in the national forests.

When treated wood is used in field settings, the possibility of environmental contamination raises concerns. 

There is increasing pressure to be environmentally 

friendly and to reduce, restrict, or eliminate the use of 

wood preservatives because of the concern that toxic 

constituents may leach from the treated wood. This 

report will provide an overview of preservative systems,

help readers understand the level of risk and status of 

the science involved in evaluating preservative systems,

and provide some guidelines for using the products.

Figure 1—A stress-laminated road bridge constructed with creosote-treated wood near the 

Glade Creek Grist Mill in Babcock State Park, WV.

1
Types of Wood Preservatives 

Wood preservatives have been used for more than 

a century. They are broadly classified as either 

waterborne or oil-type, based on the chemical 

composition of the preservative and the carrier used 

during the treating process. Some preservatives can be 

formulated for use with either water or oil solvents. 

Water-based preservatives often include some type of 

cosolvent, such as amine or ammonia to keep one or 

more of the active ingredients in solution. Each solvent 

has advantages and disadvantages that depend on the 

application.

Generally, wood preservatives also are classified or 

grouped by the type of application or exposure environment in which they are expected to provide long-term 

protection. Some preservatives have sufficient leach 

resistance and broad spectrum efficacy to protect wood

that is exposed directly to soil and water. These preservatives will also protect wood exposed aboveground, 

and may be used in those applications at lower retentions

(concentrations in the wood).

Other preservatives have intermediate toxicity or leach 

resistance that allows them to protect wood fully exposed to the weather, but not in contact with the 

ground. Some preservatives lack the permanence or 

toxicity to withstand continued exposure to precipitation, but may be effective with occasional wetting. 

Finally, there are formulations that are so readily leachable that they can only withstand very occasional, superficial wetting.

It is not possible to evaluate a preservative’s long-term 

efficacy in all types of exposure environments and 

there is no set formula for predicting exactly how long 

a wood preservative will perform in a specific application. This is especially true for aboveground applications

(figure 2) because preservatives are tested most extensively in ground contact. To compensate for this uncertainty, there is a tendency to be conservative in selecting

a preservative for a particular application. 

Figure 2—The Mocus Point Pack Bridge crosses the Lochsa River in the Clearwater National Forest, ID.

2
Oil-Type Preservatives 

The most common oil-type preservatives are creosote, 

pentachlorophenol, and copper naphthenate. Occasionally, oxine copper and IPBC (3-iodo-2-propynyl butyl 

carbamate) also are used for aboveground applications. 

The conventional oil-type preservatives, such as creosote

and pentachlorophenol solutions, have been confined 

largely to uses that do not involve frequent human contact. The exception is copper naphthenate, a preservative

that was developed more recently and has been used 

less widely. Oil-type preservatives may be visually oily, 

or oily to the touch, and sometimes have a noticeable 

odor. However, the oil or solvent that is used as a carrier

makes the wood less susceptible to cracks and checking.

This type of preservative is suitable for treatment of 

glue-laminated stringers for bridges where cracks in the

stringers could alter the bridges’ structural integrity.

Creosote

Coal-tar creosote is effective when used in ground contact, water contact, or aboveground. It is the oldest wood

preservative still in commercial use in the United States.

It is made by distilling coal tar that is created when coal

is carbonized at high temperatures (1,652 to 2,192 degrees Fahrenheit [900 to 1,200 degrees Celsius]). Unlike

other oil-type preservatives, creosote usually is not 

dissolved in oil, but it does look and feel oily. Creosote 

contains a chemically complex mixture of organic 

molecules, most of which are polycyclic aromatic hydrocarbons. The composition of creosote varies because it 

depends on how the creosote is distilled. However, the 

small differences in composition in modern creosotes do 

not affect their performance as wood preservatives. 

Creosote-treated wood is dark brown to black and has a

distinct odor, which some people consider unpleasant. 

Creosote-treated wood is very difficult to paint. Workers

sometimes object to creosote-treated wood because it 

soils their clothes and makes their skin sensitive to the 

sun. The treated wood sometimes has an oily surface. 

Types of Wood Preservatives

Patches of creosote sometimes accumulate, creating a 

hazard when it contacts the skin. Because of these 

concerns, creosote-treated wood often is not the first 

choice for applications such as bridge members or 

handrails, where there is a high probability of human 

contact. 

However, creosote-treated wood has advantages to offset

concerns with its appearance and odor. It has a lengthy 

record of satisfactory use in a wide range of applications

and is relatively inexpensive. Creosote is effective in 

protecting both hardwoods and softwoods and improving the dimensional stability of the treated wood. 

Creosote is listed in American Wood-Preservers’ Association (AWPA) Standards for a wide range of wood products created from many different species of trees. The 

minimum creosote retentions required by the standards

are in the range of 5 to 8 pounds per cubic foot (80 to 128

kilograms per cubic meter) for aboveground applications,

10 pounds per cubic foot (160 kilograms per cubic meter)

for wood used in ground contact, and 12 pounds per 

cubic foot (192 kilograms per cubic meter) for wood 

used in critical structural applications, such as highway

construction. With heated solutions and lengthy pressure

periods, creosote can penetrate wood that is fairly difficult to treat. Creosote is suitable for treatment of gluelaminated members. Creosote treatment does not accelerate, and may even inhibit, the corrosion of metal 

fasteners. 

Treatment facilities that use creosote are found throughout the United States, so this wood preservative is readily

available. Creosote is classified as a Restricted Use Pesticide (RUP) by the U.S. Environmental Protection Agency

(EPA). Producers of treated wood, in cooperation with 

the EPA, have created Consumer Information Sheets with

guidance on appropriate handling and site precautions 

when using wood treated with creosote (appendix A). 

These sheets should be available for all persons who 

handle creosote-treated wood.

3
Types of Wood Preservatives

Pentachlorophenol

Pentachlorophenol has been widely used as a pressuretreatment preservative in the United States since the 

1940s. The active ingredients, chlorinated phenols, are 

crystalline solids that can be dissolved in different types

of organic solvents. A performance of pentachlorophenol

and the properties of the treated wood are influenced 

by the properties of the solvent. 

Pentachlorophenol is effective when used in ground 

contact, freshwater, or aboveground. It is not as effective

when used in seawater. A heavy oil solvent (specified as 

Type A in AWPA Standard P9) is preferable when the 

treated wood is to be used in ground contact. Wood 

treated with lighter solvents may not be as durable. 

Wood treated with pentachlorophenol in heavy oil 

typically has a brown color, and may have a slightly oily

surface that is difficult to paint. It also has some odor, 

which is associated with the solvent. Pentachlorophenol

in heavy oil should not be used when frequent contact 

with skin is likely (handrails, for instance). Pentachlorophenol in heavy oil has long been a popular choice for

treating utility poles, bridge timbers, glue-laminated 

beams, and foundation pilings. The effectiveness of 

pentachlorophenol is similar to that of creosote in protecting both hardwoods and softwoods, and pentachlorophenol often is thought to improve the dimensional 

stability of the treated wood. 

Pentachlorophenol is listed in the AWPA standards for 

a wide range of wood products and wood species. The 

minimum softwood retentions are 0.4 pounds per cubic

foot (6.4 kilograms per cubic meter) for wood used 

aboveground, and 0.5 pounds per cubic foot (8 kilograms

per cubic meter) for wood used in critical structural 

applications or in ground contact. 

With heated solutions and extended pressure periods, 

pentachlorophenol can penetrate woods that are difficult to treat. Pentachlorophenol does not accelerate the

corrosion of metal fasteners relative to untreated wood.

The heavy oil solvent imparts some water repellency to

the treated wood. Treatment facilities in many areas of 

the United States use pentachlorophenol in heavy oil, 

making it another readily available wood preservative. 

Pentachlorophenol is most effective when applied with 

a heavy solvent, but it performs well in lighter solvents 

for aboveground applications. Lighter solvents also provide the advantage of a less oily surface appearance, 

lighter color, and improved paintability. The standards 

for aboveground minimum retentions for pentachlorophenol vary from 0.25 to 0.3 pounds per cubic foot (4 to

4.8 kilograms per cubic meter) for treatment of red oak 

to 0.4 pounds per cubic foot (6.4 kilograms per cubic 

meter) for softwood species. 

Pentachlorophenol in light oil has some similarities to 

pentachlorophenol in heavy oil. It can be used to treat 

species of wood that are difficult to treat and it does not

accelerate corrosion. Wood treated with pentachlorophenol in light oil may be used in recreational structures 

and in applications where human contact is likely, such 

as handrails, if a sealer such as urethane, shellac, latex, 

epoxy enamel, or varnish is applied. Wood treated with

pentachlorophenol in light oil may be painted or stained

after it dries. One disadvantage of the lighter oil is that 

the treated wood has less water repellency. Treatment 

facilities that use pentachlorophenol in light oil are not 

as numerous as those that use heavy oil. 

Pentachlorophenol is classified as an RUP by the EPA. 

Producers of treated wood, in cooperation with the EPA,

have created consumer information sheets with guidance

on appropriate handling and site precautions for wood 

treated with pentachlorophenol (appendix A). These 

sheets should be available for all persons who handle 

wood treated with pentachlorophenol. 

4
Copper Naphthenate

Copper naphthenate is effective when used in ground 

contact, water contact, or aboveground. It is not standardized for use in saltwater applications. Copper naphthenate’s effectiveness as a preservative has been known 

since the early 1900s, and various formulations have been

used commercially since the 1940s. It is an organometallic compound formed as a reaction product of copper

salts and naphthenic acids derived from petroleum. 

Unlike other commercially applied wood preservatives,

small quantities of copper naphthenate can be purchased

at retail hardware stores and lumberyards. Cuts or holes

in treated wood can be treated in the field with copper 

naphthenate. 

Wood treated with copper naphthenate has a distinctive

bright green color that weathers to light brown. The 

treated wood also has an odor that dissipates somewhat

over time. Depending on the solvent used and treatment

procedures, it may be possible to paint wood treated 

with copper naphthenate after it has been allowed to 

weather for a few weeks. 

Copper naphthenate can be dissolved in a variety of 

solvents. The heavy oil solvent (specified in AWPA Standard P9, Type A) or the lighter solvent (AWPA Standard P9, 

Type C) are the most commonly used. Copper naphthenate is listed in AWPA standards for treatment of major 

softwood species that are used for a variety of wood 

products. It is not listed for treatment of any hardwood 

species, except when the wood is used for railroad ties.

The minimum copper naphthenate retentions (as elemental copper) range from 0.04 pounds per cubic foot (0.6 

kilograms per cubic meter) for wood used aboveground,

to 0.06 pounds per cubic foot (1 kilograms per cubic 

meter) for wood that will contact the ground and 0.075 

pounds per cubic foot (1.2 kilograms per cubic meter) 

for wood used in critical structural applications. 

When dissolved in No. 2 fuel oil, copper naphthenate 

can penetrate wood that is difficult to treat. Copper 

naphthenate loses some of its ability to penetrate wood 

Types of Wood Preservatives

when it is dissolved in heavier oils. Copper naphthenate

treatments do not significantly increase the corrosion of

metal fasteners relative to untreated wood. 

Copper naphthenate is commonly used to treat utility 

poles, although fewer facilities treat utility poles with 

copper naphthenate than with creosote or pentachlorophenol. Unlike creosote and pentachlorophenol, 

copper naphthenate is not listed as an RUP by the EPA.

Even though human health concerns do not require 

copper naphthenate to be listed as an RUP, precautions 

such as the use of dust masks and gloves should be used

when working with wood treated with copper naphthenate. 

Oxine Copper (Copper-8-Quinolinolate)

Oxine copper is effective when used aboveground. Its 

efficacy is reduced when it is used in direct contact with

the ground or with water. It has not been standardized 

for those applications. Oxine copper (copper-8-quinolinolate) is an organometallic compound. The formulation

consists of at least 10-percent copper-8-quinolinolate, 

10-percent nickel-2-ethylhexanoate, and 80-percent inert

ingredients. It is accepted as a standalone preservative 

for aboveground use to control sapstain fungi and mold

and also is used to pressure-treat wood. 

Oxine copper solutions are greenish brown, odorless, 

toxic to both wood decay fungi and insects, and have a 

low toxicity to humans and animals. Oxine copper can 

be dissolved in a range of hydrocarbon solvents, but 

provides protection much longer when it is delivered 

in heavy oil. Oxine copper is listed in the AWPA standards for treating several softwood species used in exposed, aboveground applications. The minimum specified

retention for these applications is 0.02 pounds per cubic

foot (0.32 kilograms per cubic meter, as elemental copper). 

Oxine copper solutions are somewhat heat sensitive, 

which limits the use of heat to increase penetration of 

5
Types of Wood Preservatives

the preservative. However, oxine copper can penetrate 

difficult-to-treat species, and is sometimes used to treat 

Douglas-fir used aboveground in wooden bridges and 

deck railings. Oilborne oxine copper does not accelerate

corrosion of metal fasteners relative to untreated wood.

A water-soluble form can be made with dodecylbenzene

sulfonic acid, but the solution corrodes metals. Oxine 

copper is not widely used by pressure-treatment facilities,

but is available from at least one plant on the West Coast.

Wood treated with oxine copper presents fewer toxicity

or safety and handling concerns than oilborne preservatives that can be used in ground contact. Sometimes, it 

is used as a preservative to control sapstain fungi or 

incorporated into retail stains for siding, shingles, and 

cabin logs. Oxine copper is listed by the U.S. Food and 

Drug Administration (FDA) as an indirect additive that 

can be used in packaging that may come in direct contact with food.

Precautions such as wearing gloves and dust masks 

should be used when working with wood treated with 

oxine copper. Because of its somewhat limited use and 

low mammalian toxicity, there has been little research 

to assess the environmental impact of wood treated with

oxine copper. 

IPBC and Insecticides 

IPBC (3-iodo-2-propynyl butyl carbamate) is not intended

for use in ground contact or for horizontal surfaces that

are fully exposed to the weather. It does provide protection for wood that is aboveground and partially protected

from the weather. IPBC contains 97-percent 3-iodo-2-

propynyl butyl carbamate that includes a minimum of 

43.4-percent iodine. IPBC industrial fungicides are broadspectrum fungicidal additives used in architectural 

coatings and construction applications (such as paints, 

stains, adhesives, caulks, and sealants), textiles, and 

plastic products to prevent dry film fungal growth. 

The IPBC preservative is included as the primary fungicide in several water-repellent-preservative formulations under the trade name Polyphase and sold at retail 

stores. Although oil-soluble formulations are discussed 

in this report, water-based formulations also may be 

used. 

IPBC is colorless. Depending on the solvent and formulation, it may be possible to paint treated wood. Some 

formulations may have noticeable odor, but others may 

have little or no odor. IPBC is not an effective insecticide

and is not used as a stand-alone treatment for critical 

structural members. 

IPBC is listed as a preservative in AWPA standards, but 

no pressure-treated wood products have been standardized for IPBC. Dip-treating (a nonpressure process) with

IPBC was standardized recently for ponderosa-pine millwork at a minimum retention of 950 parts per million 

(about 0.023 pounds per cubic foot [0.37 kilograms per 

cubic meter]). Soil block tests indicate that IPBC can 

prevent fungal attack of hardwoods and softwoods when

it is used at a retention of 0.022 pounds per cubic foot 

(0.35 kilograms per cubic meter) or higher. After 9 years

of aboveground exposure tests with pressure-treated 

Douglas-fir, ponderosa pine, and western hemlock results

indicate that mixtures of IPBC and chloropyrifos can protect wood from decay at IPBC retentions as low as 0.05 

pounds per cubic foot (0.8 kilograms per cubic meter). 

Some pressure-treating facilities use a mixture of IPBC 

and an insecticide, such as permethrin or chloropyrifos, 

to treat structural members used aboveground that will 

be largely protected from the weather, although this 

practice is not a standardized treatment. These facilities

are using IPBC retentions of 0.035 pounds per cubic foot

(0.56 kilograms per cubic meter) or higher, with mineral

spirits as the solvent. The advantage of this treatment is 

that it is colorless and allows the wood to maintain its 

natural appearance. This treatment is being used on 

Western species that are difficult to treat. Very few facilities are conducting pressure treatments with IPBC.

6
IPBC has relatively low acute toxicity for mammals and 

is not classified as an EPA RUP. However, workers should

follow standard precautions, such as wearing gloves and

dust masks, when working with wood treated with IPBC.

Because IPBC typically has not been used for pressure 

treatment, there has been little evaluation of the environmental impact of wood treated with IPBC. It appears 

that IPBC degrades rapidly in soil and aquatic environments. It has low toxicity for birds, but is highly toxic to

fish and aquatic invertebrates. The relatively low IPBC 

concentrations used in the wood and its rapid degradation in the environment would be expected to limit any

environmental accumulations caused by leaching. Because

IPBC usually is used with a light solvent, the preservative

is not likely to bleed or ooze out of wood.

Waterborne Preservatives 

Waterborne preservatives react with or precipitate in 

treated wood, becoming “fixed.” They resist leaching. 

Because waterborne preservatives leave a dry, paintable

surface, they are commonly used to treat wood for residential applications, such as decks and fences. Waterborne

preservatives are used primarily to treat softwoods, 

because they may not fully protect hardwoods from 

soft-rot attack. Most hardwood species are difficult to 

treat with waterborne preservatives. 

These preservatives can increase the risk of corrosion 

when metals contact treated wood used in wet locations.

Metal fasteners, connectors, and flashing should be made

from hot-dipped galvanized steel, copper, silicon bronze,

or stainless steel if they are used with wood treated with

waterborne preservatives containing copper. Aluminum

should not be used in direct contact with wood treated 

with waterborne preservatives containing copper. Borates

are another type of waterborne preservative. However, 

they do not fix in the wood and leach readily if they are

exposed to rain or wet soil. Borate treatment does not 

Types of Wood Preservatives

increase the risk of corrosion when metals contact 

preservative-treated wood.

Chromated Copper Arsenate (CCA)

CCA protects wood used aboveground, in contact with 

the ground, or in contact with freshwater or seawater. 

Wood treated with CCA (commonly called green treated)

dominated the treated wood market from the late 1970s

until 2004. Chromated copper arsenate has been phased

out voluntarily for most applications around residential 

areas and where human contact is prevalent. The allowable uses for CCA are discussed in more detail in the 

Recommended Guidelines section. 

The three standardized formulations are: CCA Type A, 

CCA Type B, and CCA Type C. CCA Type C (CCA–C) is 

the formulation used by nearly all treatment facilities 

because of its resistance to leaching and its demonstrated

effectiveness. CCA–C is comprised of 47.5 percent chromium trioxide, 18.5 percent copper oxide, and 34.0 percent

arsenic pentoxide dissolved in water. 

CCA–C has decades of proven performance. It is the 

reference preservative used to evaluate the performance

of other waterborne wood preservatives during accelerated testing. Because it has been widely used for so many

years, CCA–C is listed in AWPA standards for a wide range

of wood products and applications. The minimum retention of CCA–C in wood ranges from 0.25 pounds per 

cubic foot (4 kilograms per cubic meter) in aboveground

applications to 2.5 pounds per cubic foot (40 kilograms 

per cubic meter) in marine applications. Most groundcontact applications require minimum retentions of 0.4 

pounds per cubic foot (6.4 kilograms per cubic meter). 

Critical structural applications require minimum retentions of 0.6 pounds per cubic foot (9.6 kilograms per 

cubic meter). It may be difficult to obtain adequate 

penetration of CCA in some difficult-to-treat species. The

chromium serves as a corrosion inhibitor. Corrosion of 

fasteners in wood treated with CCA is not as much of a 

7
Types of Wood Preservatives

concern as in wood treated with other waterborne 

preservatives that contain copper but do not contain 

chromium.

CCA contains inorganic arsenic and is classified as an RUP

by the EPA. Producers of treated wood, in cooperation 

with the EPA, created the Consumer Information Sheet 

which has been replaced with the Consumer Safety 

Information Sheet that gives guidance on handling and 

site precautions at sites where wood treated with inorganic arsenic is used (appendix B). The consumer safety

information sheet should be available to all persons who

handle wood treated with CCA.

Ammoniacal Copper Zinc Arsenate (ACZA)

Ammoniacal copper zinc arsenate (ACZA) contains 

copper oxide (50 percent), zinc oxide (25 percent), and

arsenic pentoxide (25 percent). ACZA is a refinement of

an earlier formulation, ACA, which is no longer available

in the United States. The color of the treated wood varies

from olive to bluish green. The wood may have a slight 

ammonia odor until it has dried thoroughly. ACZA is an 

established preservative that is used to protect wood 

from decay and insect attack in a wide range of exposures

and applications. Exposure tests showed that it protected

stakes and posts that contacted the ground. 

ACZA is listed in the AWPA standards for treatment of a 

range of softwood and hardwood species and wood 

products. The minimum ACZA retention is 0.25 pounds

per cubic foot (4 kilograms per cubic meter) for aboveground applications and 0.4 pounds per cubic foot (6.4 

kilograms per cubic meter) for wood that contacts the 

ground. A slightly higher retention, 0.6 pounds per cubic

foot (9.6 kilograms per cubic meter), is required for wood

used in highway construction and for critical structural

components that are exposed to high decay hazard. The

ammonia in the treating solution, in combination with 

processing techniques such as steaming and extended 

pressure periods at elevated temperatures, allow ACZA 

do a better job of penetrating difficult-to-treat species of

wood than many other water-based wood preservatives.

ACZA is used frequently in the Western United States to

treat Douglas-fir lumber and timbers used to construct

secondary highway bridges, trail bridges, and boardwalks.

The ACZA treatment can accelerate corrosion in comparison to untreated wood, requiring the use of hot-dipped 

galvanized or stainless steel fasteners. Treatment facilities

using ACZA are located in Western States, where many 

native tree species are difficult to treat with CCA. 

ACZA contains inorganic arsenic and is classified as an 

RUP by the EPA. Producers of treated wood, in cooperation with the EPA, have created consumer information 

sheets that suggest appropriate handling precautions and

precautions at sites where wood treated with inorganic 

arsenic (appendix B) will be used. These sheets should 

be available to all personnel who handle wood treated 

with ACZA. 

Alkaline Copper Quaternary (ACQ) Compounds

Alkaline copper quat (ACQ) is one of several wood 

preservatives that have been developed in recent years 

to meet market demands for alternatives to CCA. The 

fungicides and insecticides in ACQ are copper oxide (67

percent) and a quaternary ammonium compound (quat).

Many variations of ACQ have been standardized or are 

being standardized. ACQ type B (ACQ–B) is an ammoniacal copper formulation, ACQ type D (ACQ–D) is an 

amine copper formulation, and ACQ type C (ACQ–C) is 

a combined ammoniacal-amine formulation with a 

slightly different quat compound. 

Wood treated with ACQ–B is dark greenish brown and 

fades to a lighter brown. It may have a slight ammonia 

odor until the wood dries. Wood treated with ACQ–D 

has a lighter greenish-brown color and has little noticeable odor; wood treated with ACQ–C varies between 

the color of ACQ–B and that of ACQ–D, depending on 

8
Types of Wood Preservatives

the formulation. Stakes treated with these three formulations have demonstrated their effectiveness against 

decay fungi and insects when the stakes contacted the 

ground. 

The ACQ formulations are listed in the AWPA standards 

for a range of applications and many softwood species. 

The listings for ACQ–C are limited because it is the most

recently standardized. The minimum ACQ retentions are

0.25 pounds per cubic foot (4 kilograms per cubic meter)

for aboveground applications, 0.4 pounds per cubic foot

(6.4 kilograms per cubic meter) for applications involving

ground contact, and 0.6 pounds per cubic foot (9.6 kilograms per cubic meter) for highway construction. The 

different formulations of ACQ allow some flexibility in 

achieving compatibility with a specific wood species 

and application. An ammonia carrier improves the ability

of ACQ to penetrate into wood that is difficult to treat. 

For wood species that are easier to treat, such as southern pine, an amine carrier will provide a more uniform 

surface appearance. 

All ACQ treatments accelerate corrosion of metal fasteners relative to untreated wood. Hot-dipped galvanized 

copper or stainless steel fasteners must be used. The 

number of pressure-treatment facilities using ACQ is 

increasing. 

In the Western United States, the ACQ–B formulation is 

used because it will penetrate difficult-to-treat Western 

species better than other waterborne preservatives. 

Treatment plants elsewhere generally use the ACQ–D 

formulation. Researchers at the USDA Forest Service’s 

Forest Products Laboratory in Madison, WI, are evaluating the performance of a secondary highway bridge 

constructed using Southern pine lumber treated with 

ACQ–D (Ritter and Duwadi 1998). 

Copper Azoles (CBA–A and CA–B)

Copper azole is another recently developed preservative

formulation that relies primarily on amine copper, but 

with additional biocides, to protect wood from decay and

insect attack (figure 3). The first copper azole formulation

Figure 3—Pressure-treated lumber stockpiled at a lumberyard. Lumber treated with ACQ–D 

and CA–B has become widely available.

9
Types of Wood Preservatives

developed was the copper azole type A (CBA–A), which 

contains 49-percent copper, 49-percent boric acid, and 

2-percent tebuconazole. Type A is no longer used in the

United States. The copper azole type B (CA–B) formulation was standardized recently. CA–B does not contain 

boric acid. It is comprised of 96-percent copper and 4-

percent tebuconazole. Wood treated with either copper

azole formulation has a greenish-brown color and little 

or no odor.

Tests showed that the copper azole formulations protected stakes in the ground from attack by decay fungi 

and insects. The formulations are listed in the AWPA 

standards for treatment of a range of softwood species. 

Minimum CA–B retentions in the wood are 0.10, 0.21, or 

0.31 pounds per cubic foot (1.6, 3.4, or 5 kilograms per 

cubic meter) for wood used aboveground, contacting the 

ground, or in critical structural components, respectively.

Copper azole is an amine formulation. Ammonia may be

added at the treating plant when the copper azole is used

on Western species that are difficult to treat. This formulation is often used to treat Douglas-fir. Formulations with

ammonia slightly darken the surface appearance and 

initially affect the odor of the treated wood. 

Copper azole treatments increase the rate of corrosion of

metal fasteners relative to untreated wood. Appropriate 

hot-dipped galvanized steel, copper or stainless steel 

fasteners, connectors, and flashing are recommended. 

Although copper azole was introduced to North America

recently, almost 100 treating facilities now use this 

preservative.

Borates

Borate compounds are the most commonly used unfixed

waterborne preservatives. Unfixed preservatives can 

leach from treated wood. They are used for pressure 

treatment of framing lumber used in areas with high 

termite hazard, and as surface treatments for a wide range

of wood products, such as cabin logs and the interiors of

wood structures. They are also applied as internal treatments using rods or pastes. At higher rates of retention,

borates also are used as fire-retardant treatments for 

wood. 

Boron has some exceptional performance characteristics,

including activity against fungi and insects, but low 

mammalian toxicity. It is relatively inexpensive. Another

advantage of boron is its ability to diffuse with water into

wood that normally resists traditional pressure treatment.

Wood treated with borates has no added color, no odor,

and can be finished (primed and painted). 

While boron has many potential applications in framing,

it probably is not suitable for many Forest Service applications because the chemical will leach from the wood 

under wet conditions. It may be a useful treatment for 

insect protection in areas continually protected from 

water. 

Inorganic boron is listed as a wood preservative in the 

AWPA standards, which include formulations prepared 

from sodium octaborate, sodium tetraborate, sodium 

pentaborate, and boric acid. Inorganic boron is also 

standardized as a pressure treatment for a variety of 

species of softwood lumber used out of contact with the

ground and continuously protected from water. The 

minimum borate (B2O3) retention is 0.17 pounds per 

cubic foot (2.7 kilograms per cubic meter). A retention 

of 0.28 pounds per cubic foot (4.5 kilograms per cubic 

meter) is specified for areas with Formosan subterranean

termites. 

Borate preservatives are available in several forms, but 

the most common is disodium octaborate tetrahydrate 

(DOT). DOT has higher water solubility than many other

forms of borate, allowing more concentrated solutions to

be used and increasing the mobility of the borate through

the wood. With the use of heated solutions, extended 

pressure periods, and diffusion periods after treatment,

10
DOT can penetrate species that are relatively difficult to

treat, such as spruce. Several pressure treatment facilities

in the United States use borate solutions.

Although borates have low mammalian toxicity, workers

handling borate-treated wood should use standard precautions, such as wearing gloves and dust masks. The 

environmental impact of borate-treated wood for construction projects in sensitive areas has not been evaluated. Because borate-treated wood is used in areas protected from precipitation or water, little or no borate 

should leach into the environment. Borates have low 

toxicity to birds, aquatic invertebrates, and fish. Boron 

occurs naturally at relatively high levels in the environment. Because borates leach readily, extra care should 

be taken to protect borate-treated wood from precipitation when it is stored at the jobsite. Precipitation could 

deplete levels of boron in the wood to ineffective levels

and harm vegetation directly below the stored wood.

Borate-treated wood should be used only in 

applications where the wood is kept free from 

rainwater, standing water, and ground contact.

Other Waterborne Preservatives

Other waterborne preservatives have been introduced 

recently on the commercial market. They have not been

on the market long enough to have long-term performance studies completed. Their effectiveness or performance has not been established. This publication only 

describes preservatives that have been evaluated and 

standardized by the American Wood-Preservers’ Association (AWPA), the primary standard-setting body for 

pressure-treated wood. To become standardized by the 

AWPA, preservative-treated wood must undergo a series

of rigorous tests to ensure its durability. These tests 

include several years of outdoor exposure in a climate 

with severe biodeterioration hazards. The results of these

Types of Wood Preservatives

tests are reviewed by AWPA members who represent 

government agencies, universities, commercial chemical

suppliers, and treatment companies. Be wary of purchasing wood that has been treated with a preservative 

that has not been standardized for that application by 

either the AWPA or another major standard-setting body,

such as the American Society for Testing and Materials 

(ASTM).

Preservatives That Are No Longer Available 

Commercially 

Several preservative formulations that have been used in

the past were not available commercially in 2005. The 

wood preservative industry has become more dynamic 

because of economic factors and regulations. The following preservative formulations are included in this report

because they may become available in the future and 

because they have been used to treat existing structures.

Ammoniacal Copper Arsenate (ACA)

ACA was an older formulation of ACZA that didn’t contain

zinc. It has not been available in the United States for 

many years and is not likely to be produced in the future.

ACA should be replaced with ACZA in older guidelines 

and specifications. 

Acid Copper Chromate (ACC)

Acid copper chromate (ACC) has been used as a wood 

preservative in Europe and the United States since the 

1920s. ACC contains 31.8-percent copper oxide and 

68.2-percent chromium trioxide. The treated wood has 

a light greenish-brown color and little noticeable odor. 

During tests, stakes and posts that were impregnated with

ACC held up well when exposed to decay and termite 

attack, although they may have been susceptible to attack

by some species of copper-tolerant fungi. 

11
Types of Wood Preservatives

ACC is listed in the AWPA standards for a wide range of 

softwoods and hardwoods, with a minimum retention 

of 0.25 pounds per cubic foot (4 kilograms per cubic 

meter) for wood used aboveground and 0.5 pounds per 

cubic foot (8 kilograms per cubic meter) for wood that 

contacts the ground. In critical structural applications, 

such as highway construction, AWPA listings for ACC are

limited to signposts, handrails and guardrails, and gluelaminated beams used aboveground. It may be difficult 

to obtain adequate penetration of ACC in some of the 

wood species that are difficult to treat, such as white 

oak or Douglas-fir. The high chromium content of ACC 

prevents much of the corrosion that might otherwise 

occur with an acidic copper preservative.

ACC does not contain arsenic, but the treatment solution

does use hexavalent chromium. The chromium is converted to the more benign trivalent state during treatment

and storage of the wood. This process of chromium 

reduction is the basis for fixation in ACC, and depends 

on time, temperature, and moisture. Fixation standards 

or BMPs (best management practices) have not been 

developed for ACC, because of its relatively low usage. 

As a general guide, the fixation considerations discussed

for CCA can be applied to ACC, but the fixation times 

must be extended because of ACC’s higher chromium 

content. In 2005, only one manufacturer had a registration for ACC, and it was not being marketed.

Ammoniacal Copper Citrate (CC)

Ammoniacal copper citrate (CC) uses copper oxide (62 

percent) as the fungicide and insecticide, and citric acid

(38 percent) to help distribute copper within the wood 

structure. In 2004, CC was withdrawn from the AWPA 

standards because it was not being used. 

Copper Dimethyldithiocarbamate (CDDC)

Copper dimethyldithiocarbamate is a reaction product 

formed in wood that has been treated with two different

solutions. It contains copper and sulfur compounds. 

CDDC protects against decay fungi and insects. It has 

not been standardized for use in seawater. CDDC is 

standardized for treatment of southern pine and some 

other pine species at copper retentions of 0.1 pound per

cubic foot (1.6 kilograms per cubic meter) for wood used

aboveground or 0.2 pound per cubic foot (3.2 kilograms

per cubic meter) for wood that contacts the ground. 

CDDC-treated wood has a light brown color and little or

no odor. CDDC was introduced several years ago, but 

because of the expense of converting plants for its use 

and of the two-step treatment process, CDDC-treated 

wood was not available commercially in 2005.

12
Summary of Preservative Properties 

Table 1 summarizes the properties of the most commonly

used preservatives.

Table 1—The properties and uses of common preservatives.

Solvent Color Odor Fastener use characteristics 

*

Standardized Preservative Surface/handling 

restrictions corrosion

All uses Creosote Oil-type Oily, not for fre- Dark brown Strong, No worse than 

quent human lasting untreated 

contact

All uses Ammoniacal Water Dry, but Brown, Mild, Worse than 

copper zinc contains possible short term untreated 

arsenate arsenic blue areas wood

All uses Chromated Water Dry, but uses Greenish None Similar to

copper are restricted brown, untreated

arsenate by the EPA weathers wood

to gray

All uses Pentachlor- No. 2 Oily, not for fre- Dark brown Strong, No worse than

(except in ophenol in fuel oil quent human lasting untreated

seawater) heavy oil contact wood

All uses Copper No. 2 Oily, not for fre- Green, Strong, No worse than

(except in naphthenate fuel oil quent human weathers to lasting untreated

seawater) contact brownish wood

gray

All uses Alkaline Water Dry, okay Greenish Mild, Worse than 

(except in copper for human brown, short term untreated

seawater) quat contact weathers wood

to gray

All uses Copper Water Dry, okay Greenish Mild, Worse than 

(except in azole for human brown, short term untreated

seawater) contact weathers wood

to gray

Aboveground, Pentachlor- Mineral Dry, okay Light brown, Mild, No worse than

fully exposed ophenol in spirits for human weathers short term untreated

light oil contact to gray wood

if coated

Aboveground, Oxine Mineral Dry, okay Greenish Mild, No worse than

fully exposed copper spirits for human brown, short term untreated

contact weathers wood

to gray

Aboveground, IPBC + Mineral Dry, okay Colorless Mild, No worse than 

partially permethrin spirits for human short term untreated

protected contact wood

(such as

millwork)

Indoors Borates Water Dry, okay Colorless, None No worse than 

(usually for for human blue dye untreated

insect contact often added wood

protection)

*A few uses of chromated copper arsenate are still allowed for treatment of sawn products less than 5 inches thick (12.7 centimeters, 

such as dimension lumber). Pilings, poles, large timbers, and plywood are still allowed for highway construction.—Courtesy of USDA 

Forest Service, Forest Products Laboratory

13
Treatment Processes 

Methods that preserve wood generally are either: 

• Pressure processes, in which the wood is impregnated

in closed vessels at pressures considerably higher than

atmospheric pressure

• Processes that do not involve pressure

Pressure Processes 

In commercial practice, wood usually is treated by 

immersing it in preservative in an apparatus that applies

high pressure, driving the preservative into the wood. 

Pressure processes differ in details, but the general principle is the same. The wood is carried on cars or trams 

into a long steel cylinder, which is closed and filled with

preservative. Pressure forces the preservative into the 

wood until the desired amount has been absorbed and 

has penetrated relatively deeply. Commonly, three general

pressure processes are used: full cell, modified full cell,

and empty cell. Commercial treaters often use variations

or combinations of these processes. 

Full-Cell Processes

The full-cell (Bethel) process is used when the goal is for

wood to retain as much of the preservative as possible. 

For instance, it is a standard procedure to treat timbers 

with creosote using the full-cell process to protect the 

timbers from marine borers. Waterborne preservatives 

sometimes are applied by the full-cell process. Preservative retention can be controlled by regulating the concentration of the treating solution. The steps in the full-cell

process are: 

1. Wood is sealed in the treatment cylinder and a preliminary vacuum is applied for a half an hour or longer to 

remove the air from the cylinder and as much air as 

possible from the wood.

2. The preservative (at ambient temperature or higher, 

depending on the system) is pumped into the cylinder

without breaking the vacuum.

3. After the cylinder is filled, pressure is applied until 

the wood will take no more preservative or until the 

required retention of preservative has been achieved.

4. After pressure has been applied for the specified time,

the preservative is pumped from the cylinder.

5. A short final vacuum may be used to remove dripping

preservative from the wood.

Modified Full-Cell Processes

The modified full-cell process is basically the same as 

the full-cell process except that it uses lower levels of 

initial vacuum and often uses an extended final vacuum.

The amount of initial vacuum is determined by the wood

species, material size, and retention desired. Residual air

in the wood expands during the final vacuum to drive 

out part of the injected preservative solution. For this 

reason, modified full-cell schedules are sometimes called

low-weight schedules. They are now the most common

method of treating wood with waterborne preservatives.

Empty-Cell Processes

The empty-cell process is designed to obtain deep penetration with a relatively low net retention of preservative.

The empty-cell process should always be used for treatment with oil preservatives if it provides the desired

retention. 

Two empty-cell processes, the Rueping and the Lowry, 

are commonly employed; both use the expansive force 

of compressed air to drive out part of the preservative 

absorbed during the pressure period. The Rueping 

14
empty-cell process, often called the empty-cell process 

with initial air, has been widely used for many years in 

Europe and the United States. The following general 

procedure is employed:

1. Air under pressure is forced into the treatment cylinder,

which contains the wood. The air penetrates some 

species easily, requiring just a few minutes of application pressure. In treating the more resistant species,

the common practice is to maintain air pressure from

half an hour to 1 hour before pumping in the preservative, although the need to maintain air pressure for 

longer than a few minutes does not seem to be fully 

established. The air pressures employed generally 

range between 25 to 100 pounds per square inch (172

to 689 kilopascals), depending on the net retention 

of preservative desired and the resistance of the wood.

2. After the period of preliminary air pressure, preservative is forced into the cylinder. As the preservative is 

pumped in, air escapes from the treatment cylinder 

into an equalizing tank (also known as a Rueping tank)

at a rate that keeps the pressure constant in the cylinder. When the treatment cylinder is filled with preservative, the treatment pressure is increased above the 

initial air pressure and is maintained until the wood 

absorbs no more preservative, or until enough preservative has been absorbed for the required retention of

preservative.

3. At the end of the pressure period, the preservative is 

drained from the cylinder, and surplus preservative 

is removed from the wood with vacuum. From 20 to 

60 percent of the total preservative injected into the 

cylinder can be recovered after the vacuum has been 

applied.

Treatment Processes

Treating Pressures and Preservative Temperatures

The pressures used in treatments vary from about 50 to

250 pounds per square inch (345 to 1,723 kilopascals), 

depending on the species and the ease with which the 

wood takes the treatment; pressures commonly range 

from about 125 to 175 pounds per square inch (862 to 

1,207 kilopascals). Many woods are sensitive to (and 

could be damaged by) high treatment pressures. Heated

preservatives are used sometimes to improve penetration,

but the elevated temperatures can affect the wood’s 

properties and the stability of the treatment solution. 

The AWPA specifications require that the temperature of

the preservative during the entire pressure period not 

exceed 120 degrees Fahrenheit (49 degrees Celsius) for 

ACC and CCA and 150 degrees Fahrenheit (60 degrees 

Celsius) for ACQ–B, ACQ–D, ACZA, CBA–A, CA–B, and 

CDDC. The maximum temperature for inorganic boron

is 200 degrees Fahrenheit (93 degrees Celsius). Please 

refer to the Wood Handbook for more information on 

treating pressures and temperatures. 

Penetration and Retention

Penetration and retention requirements are equally 

important in determining the quality of preservative 

treatment. Penetration levels vary widely, even in pressure-treated material. In most species, heartwood is more

difficult to penetrate than sapwood. In addition, species 

differ greatly in the degree to which their heartwood 

may be penetrated. Incising (perforating the surface of 

the wood with small slits) tends to improve the penetration of preservative in many refractory species, but 

species that are highly resistant to penetration will not 

have deep or uniform penetration, even when they are 

incised. When the heart faces of these species are not 

incised, penetration may be as deep as 1⁄

4 inch (6 millimeters), but often is not more than 1⁄

16 inch (1.6 millimeters).

15
Treatment Processes

Experience has shown that even slight penetration has 

some value, although deeper penetration is highly desirable to prevent untreated wood from being exposed when

the wood checks, particularly for important members 

that are costly to replace. The heartwood of coastal 

Douglas-fir, southern pines, and various hardwoods, 

although resistant, will frequently show transverse penetrations of 6 to 12 millimeters (1⁄

4 to 1⁄2 inch) and sometimes penetrations that are considerably deeper.

Complete penetration of the sapwood should be the ideal

in all pressure treatments. This penetration often can be

accomplished in small-size timbers of various commercial

woods. With skillful treatment, it may be obtained in 

pilings, ties, and structural timbers. However, the operator cannot always ensure complete penetration of sapwood in every large piece of round material with thick 

sapwood, such as poles and piles. Specifications permit 

some tolerance for less than complete penetration. Refer

to the AWPA standards for required penetration and 

retention of various species and treatments.

Nonpressure Processes 

The numerous nonpressure processes differ widely in the

penetration and retention levels that may be achieved, 

and in the degree of protection they provide. When 

similar retention and penetration levels are reached, the

service life of wood treated by a nonpressure method 

should be comparable to that of wood treated by a 

process that uses pressure. Nevertheless, nonpressure 

treatments, particularly those involving surface applications, generally do not produce results as satisfactory as

those produced by pressure treatments. The nonpressure

processes do serve a useful purpose when more thorough

treatments are impractical or when little protection is 

required.

In general, nonpressure methods consist of: 

• Surface application of preservatives by brushing or 

brief dipping

• Soaking wood in preservative oils or steeping it in 

solutions of waterborne preservatives

• Diffusion processes using waterborne preservatives

• Vacuum treatment

• Other miscellaneous processes

Surface Applications

The simplest treatment is to dip wood into preservative

or to brush preservative on the wood. Preservatives that

have low viscosity when cold should be used, unless the

preservative can be heated. The preservative should be 

flooded over the wood rather than merely painted. Every

check and depression in the wood should be thoroughly

filled with the preservative. Any untreated wood that is 

left exposed will provide ready access for fungi. 

Rough lumber may require as much as 10 gallons of oil 

per 1,000 square feet (40 liters of oil per 100 square 

meters) of surface. Surfaced lumber requires considerably

less oil. The transverse penetration usually will be less 

than 1⁄

10 inch (2.5 millimeters), although in easily penetrated species, end-grain (longitudinal) penetration will

be considerably deeper. The additional life obtained by 

such treatments will be affected greatly by the conditions

of service. For treated wood that contacts the ground, 

service life may be from 1 to 5 years.

Dipping wood for a few seconds to several minutes in a

preservative provides more assurance that all surfaces 

and checks will be thoroughly coated with the preservative. In addition, dipping usually produces slightly deeper

penetration. Window sashes, frames, and other millwork

commonly are treated by dipping them in a water-repellent preservative, either before or after assembly. Transverse penetration of the preservative applied by brief 

dipping is very shallow, usually less than a few hun16
dredths of an inch (a millimeter). The exposed end 

surfaces at joints are the most vulnerable to decay in 

millwork products. Good end-grain penetration is especially important.

Dip applications provide very limited protection to wood

that contacts the ground or that is used in very moist 

conditions. They provide very limited protection against

attack by termites. However, they do have value for 

exterior woodwork and millwork that is painted, that 

does not contact the ground, and that is exposed to 

moisture just for brief periods.

Cold Soaking and Steeping

Cold soaking well-seasoned wood for several hours or 

days in low-viscosity preservative oils or steeping green

or seasoned wood for several days in waterborne preservatives has provided varying levels of success for fenceposts, lumber, and timbers.

Pine posts treated by cold soaking for 24 to 48 hours or 

longer in a solution containing 5 percent of pentachlorophenol in No. 2 fuel oil have had an average life of 16 

to 20 years or longer.

The sapwood in these posts was well penetrated with 

retention levels of the preservative solution ranging from

2 to 6 pounds per cubic foot (32 to 96 kilograms per 

cubic meter). Posts of woods such as birch, aspen, and 

sweetgum treated by this method have deteriorated 

much more quickly than treated pine posts.

Preservative penetration and retention levels obtained by

cold soaking lumber for several hours are considerably 

better than those obtained by brief dips. However, preservative retention levels seldom equal those obtained 

by pressure treatment, except in cases such as the sapwood of pines that has become highly absorbent because

of infection by molds and stains.

Treatment Processes

Steeping wood in waterborne preservatives has had very

limited use in the United States, but it has been used for

many years in Europe. When seasoned wood is treated, 

both the water and the preservative salt soak into the 

wood. When green wood is treated, the preservative only

enters the wood by diffusion. Preservative retention and

penetration levels vary widely. The process generally is 

not recommended when more reliable treatments are 

practical.

Diffusion Processes

Diffusion processes may be used with green or wet wood.

These processes employ waterborne preservatives that 

will diffuse out of the water in a treatment paste (or 

treatment solution) into water in the wood.

The double-diffusion process developed by the Forest 

Products Laboratory has produced good results in tests 

of fenceposts and standard 2- by 4-inch (38- by 89-millimeter) stakes, particularly for full-length immersion 

treatments. This process consists of steeping green or 

partially seasoned wood first in one chemical solution, 

then in another.

The two chemicals diffuse into the wood, and react to 

precipitate an effective preservative with high resistance

to leaching. The process has had commercial application

in cooling towers and fenceposts where preservative 

protection is needed. The chemicals evaluated by the 

Forest Products Laboratory for the double-diffusion 

process are not registered by the EPA for this type of 

application. 

Other diffusion processes involve applying preservatives

to the butt or around the groundline of posts or poles. 

The preservative can be injected into standing poles at 

the groundline with a special tool, applied on the poles’

surface as a paste or bandage, or poured into holes bored

in the pole at the groundline. These treatments are 

17
Treatment Processes

valuable for untreated standing poles and for treated poles

when preservative retention levels are inadequate.

Vacuum Processes

The vacuum process, or VAC–VAC as it is called in Europe, 

has been used to treat millwork with water-repellent 

preservatives and to treat construction lumber with 

waterborne and water-repellent preservatives.

In treating millwork, the objective is to use a limited 

quantity of water-repellent preservative and obtain retention and penetration levels similar to those obtained by 

dipping for 3 minutes. The vacuum process treatment 

is included in WDMA I.S. 4–05 for Water Repellent 

Preservative Non Pressure Treatment for Millwork. 

After a quick, low initial vacuum, the cylinder is filled 

with preservative under vacuum, the vacuum is released

and preservative soaks into the wood, followed by a final

vacuum. The treatment is better than the 3-minute dip 

treatment. Penetration and retention are better, and the

surface of the wood dries quickly, leaving it ready for 

glazing, priming, and painting. The vacuum treatment is

also reported to be less likely than dip treatment to leave

objectionably high levels of preservative in bacteriainfected wood, referred to as sinker stock.

When pressure treatment is not required, lumber intended for buildings may be treated by the vacuum 

process. The process uses a higher initial vacuum and 

a longer immersion or soaking period than used in 

treating millwork.

Preservative retention is harder to control in vacuum 

treatment than in empty-cell pressure treatment. However, the concentration of waterborne preservatives can

be adjusted to provide good control over retention levels

during vacuum treatment. 

Other Nonpressure Processes

Several other nonpressure methods of various types have 

been used. Some involve applying waterborne preservatives to living trees. The Boucherie process for treating 

green, unpeeled poles has been used in Europe for many

years. This process involves attaching liquid-tight caps 

to the butt ends of the poles. A waterborne preservative

is forced under hydrostatic pressure into the cap and 

into the pole.

A tire-tube process is a simple adaptation of the Boucherie process used for treating green, unpeeled fenceposts.

In this treatment, a section of used inner tube is fastened

tight around the butt end of the post to make a bag that

holds a solution of waterborne preservative. This process

has limitations in the United States because preservative

can leak into the soil at the treatment site.

Refer to the Wood Handbook for more information on 

treatment processes.

18
Alternatives to Treated Wood 

Alternatives to treated wood are being used more resistant species is durable. The decay resistance of the 

frequently. Examples of alternatives to treated wood heartwood of native species is listed and described in 

are native decay-resistant woods, exotic decay-resis- the Wood Handbook and AASHTO standard specificatant woods, composite woods (plastic woods), vinyl, tion, M 168.

and rubber (figure 4). Only the heartwood of decayFigure 4—Alternatives to treated wood include rubber wood and solid- and hollow-core 

plastic-wood composite decking.

19
Alternatives to Treated Wood

Table 2 lists the advantages and disadvantages of different

alternatives to treated wood.

Table 2—Advantages and disadvantages of five alternatives to treated wood.

Material Description Advantages Disadvantages

Native Redwood, cedar, juniper, Resistant to decay and insects. Expensive. Surfaces may be soft 

decay-resistant bald cypress, pacific yew, Attractive. Dimensionally (susceptible to denting and scratchwoods chestnut, black locust, osage stable. Provides a use for ing). Susceptible to moisture. Life 

orange, black walnut. invasive species, such as expectancy is not as long as that of 

locust and juniper. treated wood.

Exotic Includes mahogany and a Durable. Resistant to decay and Expensive. Difficult to work with 

decay-resistant variety of ironwoods (Ipe), insects. Attractive. Virtually (requires predrilling for fasteners).

woods also known as Pau Lope. knot free. Resistant to water. Environmental concerns (except

for lumber certified by the Forest

Stewardship Council).

Composites Solid material made of wood , Doesn’t split or chip. Variety of Expensive. Unnatural appearance.

(plastic woods) fibers and recycled grocery bags colors to choose from. Less Generally not rated for structural

recycled milk jugs, or virgin plastic. need for sealing or staining. use. (Usually, wood is used for strucRequires little maintenance. tural supports and subframes.) SusFree of knots. ceptible to mildew, mold, and stains.

Color fades in sunlight. (Some products are reinforced with fiberglass

and meet ASTM standards.)

Virgin vinyl Hollow building material, a Doesn’t warp, split, chip, or rot. Expensive. Unnatural appearance.

molecularly bonded blend of Variety of colors to choose Not rated for structural use. (Wood

100-percent virgin, hi-polymer from. Never needs sealing or is required for structural supports

resin. (Some are made with UV staining. and subframes.)

inhibitors to prevent damage

from sunlight and impact modifiers for greater strength.)

High-density Thermoplastic. Weather resistant. Can be cut or Susceptible to stress cracking. Not

polyethylene drilled cleanly. No grain to as stiff as polypropylene. High mold

(HDPE) split or chip. No need to predrill shrinkage. Poor UV resistance. Not

lumber. Suitable for agricultural rated for structural use. (Wood is

uses. Good at low temperatures. required for structural supports

Impact resistant. Excellent and subframes.)

chemical resistance.

Rubber lumber Composed of 50-percent plastic Durable. Impervious to water. Unnatural appearance. Color isn’t

and 50-percent old tires. Resistant to insects. Resistant guaranteed to last. Not rated for

to UV rays. Variety of colors. structural use. (Wood is required for

Uses recycled materials. structural supports and subframes.)

—Courtesy of the U.S. Environmental Protection Agency with the addition of information on the naturally decay-resistant hardwoods.

20
Leaching and Its Effects on the Environment 

All wood-preservative treatments contain active 

ingredients that protect the wood from insects and 

fungi. Preservatives intended for use outdoors (figure

5) have chemical properties that are intended to keep 

the active ingredients in the wood and minimize leaching.

Past studies indicate that a small percentage of the active

ingredients of all types of wood preservatives leach out 

of the wood. 

Figure 5—Stairs on the Falls of Hills Creek Trail in the Monongahela 

National Forest, WV.

The amount of leaching from a particular product used 

in a specific way depends on factors such as fixation 

conditions, the preservative’s retention in the wood, the

product’s size and shape, the type of exposure, and the 

years in service. Some ingredients in all preservatives 

are toxic at high concentrations to a variety of organisms.

Laboratory studies indicate that the levels of preservatives

leached from treated wood generally are too low to 

create a biological hazard.

In recent years, several studies have been conducted on

preservative releases from structures and on the environmental consequences of those releases. For instance, the

Forest Service, the Bureau of Land Management, and 

industry partners cooperated to study the environmental 

impacts of waterborne preservatives that leached from 

wood used to construct a wetland boardwalk (USDA 

Forest Service Forest Products Laboratory 2000). The 

construction project was considered a worst case because

a lot of treated wood was used and the site had high 

rainfall. 

Separate boardwalk test sections were constructed using

untreated wood and wood treated with ACQ–B, ACZA, 

CCA–C, or CDDC. Surface soil, sediment, and water 

samples were removed before construction and at intervals after construction to determine the concentrations 

and movement of preservative elements that leached 

from the boardwalk. Aquatic insect populations in the 

vegetation, in sediments, and on artificial substrates 

were monitored. 

During the first year, each of the preservatives evaluated

released measurable amounts of copper, chromium, zinc, 

or arsenic into rainwater collected from the wood. Each

preservative also appeared to elevate soil and sediment 

levels of the elements used in the preservative. In some 

cases, levels appeared to peak soon after construction. 

In other cases, levels appeared to increase during the 

course of the year. 

With few exceptions, the elevated concentrations were 

confined to areas near the boardwalk. These levels of 

environmental accumulation did not appear to have any

measurable biological impact. Although seasonal fluctuations in insect populations were noted, none of the 

invertebrate taxa evaluated were significantly reduced 

in the wetlands surrounding any of the treated wood.

21
Leaching and Its Effects on the Environment

Brooks (2000) evaluated the environmental effects of 

timber bridges treated with either CCA–C, pentachlorophenol, or creosote. In that study, bridges that had been

in service for several years were evaluated by comparing

upstream and downstream levels of preservative concentrations in sediments and populations of aquatic insects

at the same sampling locations. 

The two bridges treated with pentachlorophenol were in

forested areas in Washington and Oregon. The Washington site appeared to contain low levels of pentachlorophenol, although the concentrations detected were 

approaching the lower detection limit of the instrumentation. No biological effects would be expected at those

levels, and none were detected. 

At the bridge treated with pentachlorophenol in Oregon,

sediment samples were collected underneath the bridge

and 3 feet (0.9 meter) downstream from the bridge. These

samples contained slightly elevated levels of pentachlorophenol. Small decreases in several biological indices 

were noted directly under the bridge, but these decreases

appeared to be related to differences in stream bottom 

habitat. No adverse effects on biological organisms were

noted when a laboratory bioassay was conducted on 

sediments collected under the bridge (Brooks 2000). 

Two CCA-treated bridges in Florida were also evaluated,

one over a saline bay and the other over a freshwater 

marsh (Brooks 2000). The bridge over the bay was in 

the final stages of construction, while the bridge over 

the marsh had been built 2 years before. Some samples 

of sediments removed within 10 feet (3 meters) of the 

newly constructed bridge contained elevated levels of 

copper, chromium, and arsenic. The patchy nature of 

the samples with elevated levels and the observation of 

wood chips in the sediments led Brooks to suspect that 

at least a portion of the elevated samples contained 

treated wood sawdust. Despite the elevated levels of 

CCA detected in the sediments, no adverse biological 

effects were observed. 

Very slightly elevated copper, chromium, and arsenic 

levels also were noted in sediments within 10 to 20 feet

(3 to 6 meters) of the 2-year-old bridge, but again, no 

adverse biological effects were observed. In this case, 

the population and diversity of aquatic insects actually 

appeared to increase closer to the bridge. 

Brooks also evaluated two creosote-treated bridges in 

agricultural areas in Indiana. One had been in service for

about 2 years and the other for about 17 years. In each 

case, elevated levels of polycyclic aromatic hydrocarbons

were detected in sediments 6 to 10 feet (1.8 to 3 meters)

downstream from the bridges. Levels of polycyclic aromatic hydrocarbons at the newer bridge approached 

levels of concern. No significant effect on insect populations was noted downstream from the newer bridge. 

The population and diversity of aquatic insects appeared

to be reduced within 20 feet (6 meters) downstream 

from the older creosote-treated bridge. 

The author postulated that this trend was caused by the

deposition of maple leaves in this area and was not a 

response to the polycyclic aromatic hydrocarbons that 

had been released (Brooks 2000). Sediments from that 

area did not adversely affect aquatic invertebrates in a 

laboratory bioassay, supporting Brooks’ hypothesis. 

The release and biological impacts of creosote also have

been evaluated for newly installed six-piling dolphins 

(clusters of pilings used as moorings or bumpers) installed in the waters of Sooke Basin on Vancouver Island,

BC, Canada (Goyette and Brooks 1998). Polycyclic aromatic hydrocarbon contamination was detected within 

25 feet (7.5 meters) downstream from the piling, and 

22
significant biological effects were noted within 2.1 feet 

(0.65 meters) of the perimeter of the structure. Slight 

biological effects were noted in laboratory bioassays of 

sediments from up to 6.6 feet (2.0 meters) downstream 

from the pilings, but not in samples of organisms collected there (Goyette and Brooks 1998).

These recent studies of the environmental impact of 

treated wood reveal several key points:

• All types of treated wood evaluated release small 

amounts of preservative components into the environment. These components can be detected in soil or 

sediment samples.

• Shortly after construction, elevated levels of preservative components sometimes can be detected in the 

water column. Detectable increases in soil and sediment concentrations of preservative components 

generally are limited to areas close to the structure.

• The leached preservative components either have low

water solubility or react with components of the soil 

or sediment, limiting their mobility and the range of 

environmental contamination.

• The levels of these components in the soil immediately

adjacent to treated structures can increase gradually 

over the years.

Although elevated preservative levels have been detected

in sediments adjacent to treated wood in aquatic environments, Brooks (Brooks 2000, USDA Forest Products 

Laboratory 2000) did not find any measurable impact 

on the abundance or diversity of aquatic invertebrates 

associated with those sediments. In most cases, levels 

of preservative components were below levels that might 

Leaching and Its Effects on the Environment

be expected to affect aquatic life. Samples with elevated

levels of preservative components tended to be limited 

to fine sediments beneath stagnant or slow-moving 

water where the invertebrate community is somewhat 

tolerant of pollutants. 

All construction materials, including the alternatives to 

treated wood, have some type of environmental impact.

Leaching from plastic and wood-plastic composites has 

not been studied as thoroughly as that from treated wood,

but one study found that over 70 different contaminants

were released from one type of recycled plastic lumber 

(Weis and others 1992). Releases from recycled plastic 

may depend on the types of chemicals that were stored

in the containers originally. Production of concrete and

steel requires mining (Mehta 2001), consumes energy, 

and contributes to the production of greenhouse gases. 

Conditions with a high potential for leaching and a high

potential for metals to accumulate are the most likely to

affect the environment. For typical Forest Service applications, these conditions are most likely to be found in 

boggy or marshy areas with little water exchange. Water

at these sites has low pH and high organic acid content,

increasing the likelihood that preservatives will be 

leached from the wood. In addition, the stagnant water 

prevents dispersal of any leached components of preservatives, allowing them to accumulate in soil, sediments,

and organisms near the treated wood.

Riparian zones, wetlands, and meadows may provide 

essential habitat for key species during critical periods 

of their life cycles. Boardwalks and fishing platforms are

commonly used in these areas. The challenge is to use 

the most durable, esthetically pleasing, cost-effective 

materials available, while still protecting sensitive ecosystems.

23
Recommended Guidelines 

The following guidelines can help field employees 

select wood preservatives that are most appropriate

for their projects (figure 6).

Selecting a Wood Preservative 

The type of preservative that is most appropriate depends

on the species of wood being treated, the type of structure, the cost, the availability of treated wood, and the 

specific area where the wood will be used.

Wood Species

Generally, hem-fir (hemlock and fir) and southern pine 

can be treated adequately with any of the commercial 

wood preservatives, although copper napthenate has 

not been standardized for use with hem-fir. CCA is not 

recommended for treatment of Douglas-fir, which is more

readily treated with oil-type or ammoniacal preservatives.

CCA is not recommended for treating hardwoods that 

will contact the ground.

Types of Structures

Although appearance is not a major concern in many 

applications, wood treated with ammoniacal copper 

preservatives (ACZA, ACQ–B) may not be colored as 

uniformly as wood treated with other waterborne preservatives. However, ammoniacal preservatives allow 

better penetration and treatment of larger material, such

as pilings and timbers—especially those made from 

Douglas-fir.

Often, large glue-laminated timbers (those used in bridge

supports, for instance) are treated with oil-type preservatives, such as pentachlorophenol and copper naphthenate

to reduce problems with checking and cracking. Laminated members, except for those that are small and 

straight, should not be treated with waterborne preservatives. The characteristic odor and appearance of 

oilborne preservatives may make them less desirable in 

areas of frequent human contact, such as handrails or 

decks.

In marine construction, or construction in areas with 

brackish water, such as ocean estuaries, only creosote, 

Figure 6—A viewing platform in the Garden of the Gods in the Shawnee National Forest, IL.

24
Recommended Guidelines

CCA, and ACZA are approved for use. In some areas 

south of a line connecting San Francisco and Virginia, 

dual treatments of creosote and one of the waterborne 

treatments may be needed to prevent attack by the 

different types of marine borers.

Ecosystem Sensitivities

Although largely undocumented, some preservatives may

be more appropriate than others in sensitive ecosystems

(figure 7). For example, CCA has a much lower copper 

content than other waterborne preservatives (except the

borates). Although there is no evidence at this time to 

suggest that any of the wood preservatives leach enough

copper to harm terrestrial or freshwater ecosystems, CCA

may pose less of a threat to aquatic ecosystems than 

preservatives with more copper.

Similarly, preservatives without arsenic may pose less of

a threat to mammals (including construction workers) 

than those that do contain arsenic. Once again, there is

no evidence that wood preservatives containing arsenic

harm people or other mammals if they are used as intended.

Wood treated with oilborne preservatives often produces an oily surface sheen when installed in stagnant

freshwater environments. This may be unacceptable in 

some situations. Waterborne preservatives may be more

appropriate when the treated wood will have extensive

contact with freshwater. 

As more information is obtained about the leaching rates

and biological impacts of treated wood, it will be possible

to make more informed decisions about the appropriate

use of wood preservatives in sensitive ecosystems. 

Managers can use computer models at the Western Wood

Preservers Institute Web site (http://www.wwpinstitute.

org) to help them make decisions about the use of 

treated wood in aquatic ecosystems. 

Purchasing Treated Wood Products 

Regardless of the type of preservative, the wood should

be treated properly and allowed to fix before it is placed

in service.

Figure 7—A boardwalk on the Trail of Blue Ice in the Chugach National Forest, AK.

25
Recommended Guidelines

Treatments

The AWPA Commodity (C) Standards have been replaced

by the Use Category System (UCS) Standards U1 and T1.

The new basic standard for specifying treated wood 

products is U1. The new basic standard with all of the 

requirements for producing treated wood is T1. The UCS

was developed as a format revision of the Commodity (C)

Standards. The UCS contains descriptions of the service

conditions for use categories, a guide to commodity 

specifications for the end uses of treated wood, a list of 

AWPA standardized preservatives, and various commodity

specifications relating to specific product types, such as

sawn products, utility poles, pilings, or fire-retardant 

applications. The UCS helps specifiers and users select 

the appropriate treatment.

Simplicity is the primary advantage of the UCS. All treated

wood products can be placed into one of five use categories, based on the hazard of biodeterioration and 

expected product performance. Products treated with 

fire retardants are placed in their own use category class.

With changes taking place rapidly in the wood-treatment

industry, it is more important than ever to ensure that 

wood is treated to standard specifications. The U.S. 

Department of Commerce American Lumber Standard 

Committee (ALSC) accredits third-party inspection 

agencies for treated wood products. Updated lists of 

accredited agencies can be found on the ALSC Web site 

(http://www.alsc.org). The easiest way to know whether

wood has been treated to standard specifications is to 

look for a quality mark or the symbol of an ALSC-accredited agency on the front or back of the end tag. Avoid 

wood that is purported to be treated to refusal (treated

until it will no longer absorb preservative).

Incising is a technique that increases preservative penetration and retention in species such as Douglas-fir. 

Douglas-fir should be incised regardless of the type of 

preservative used. Incising is especially important in 

larger material, such as timbers, that contact the ground.

Smaller material that is not in contact with ground or 

water, such as decking, may perform adequately in some

applications without incising. Although the AWPA 

Standards do not require southern pine to be incised, 

incising is beneficial when larger dimension material is 

treated. Larger pieces of material often have at least one

face with exposed heartwood that preservatives have a 

hard time penetrating. The availability of incised southern

pine is extremely limited. Table 3 summarizes the use 

categories for treated wood, while table 4 summarizes 

the standard preservative formulations and retentions 

for typical Forest Service applications.

26
Recommended Guidelines

Table 3—Service conditions for use category designations. This summary was prepared by the American Wood-Preservers’ Association and 

is used with the association’s permission.

j

j

j

j

j

Use Common agents

category Service conditions Use environment of deterioration Typical applications

UC1 Interior construction, Continuously protected Insects Interior construction and 

aboveground, dry from weather or other furnishings

sources of moisture

UC2 Interior construction, Protected from weather, Decay fungi Interior construction

aboveground, damp but may be sub ect to and insects

sources of moisture

UC3A Exterior construction, Exposed to all weather Decay fungi Coated millwork, 

aboveground, coated, cycles, but not exposed and insects siding, and trim

rapid water runoff to prolonged wetting

UC3B Exterior construction, Exposed to all weather Decay fungi Decking, deck joists,

aboveground, uncoated, cycles, including and insects railings, fence pickets,

or poor water runoff prolonged wetting and uncoated millwork

UC4A Ground contact or Exposed to all weather Decay fungi Fence, deck, and guardrail 

freshwater, noncritical cycles, normal exposure and insects posts, crossties, and utility

components posts (low-decay areas)

UC4B Ground contact or Exposed to all weather Decay fungi and Permanent wood foundations, 

freshwater, components cycles, high decay insects, increased building poles, horticultural

that are critical or potential, includes potential for posts, crossties, and utility

difficult to replace saltwater splash biodeterioration poles (high decay areas)

UC4C Ground contact, Exposed to all weather Decay fungi and Land or freshwater pilings,

freshwater, critical cycles, severe environ- insects, extreme foundation pilings, crossties,

structural components ments, extreme decay potential for biode- and utility poles (severe

potential terioration decay areas)

UC5A Salt or brackish water Continuous marine Saltwater organisms Pilings, bulkheads, and 

and ad acent mud exposure (saltwater) bracing

zone, northern waters

UC5B Salt or brackish water Continuous marine Saltwater organisms, Pilings, bulkheads, and 

and ad acent mud zone, exposure (saltwater) including creosote- bracing

New Jersey to Georgia, tolerant Limnoria

and south of San Francisco tripunctata

UC5C Salt or brackish water and Continuous marine Saltwater organisms, Pilings, bulkheads, and 

ad acent mud zone, south exposure (saltwater) including Martesia bracing

of Georgia, Gulf Coast, and Sphaeroma

Hawaii, and Puerto Rico

UCFA Fire protection as required Continuously protected Fire Roof sheathing, roof trusses, 

by codes, aboveground, from weather or other studs, joists, and paneling

interior construction sources of moisture

UCFB Fire protection as required Sub ect to wetting Fire Vertical exterior walls, inby codes, aboveground, roof surfaces, or other

exterior construction types of construction that

allow water to drain quickly

27
Recommended Guidelines

Table 4—Standardized preservative formulations and retentions for typical Forest Service applications. Specified retentions may vary with 

wood species and particular applications. These formulations are listed in the AWPA standards. PCF stands for pounds per cubic foot.

3 205

1

2

3

3

3 3

205

4 4 4

5

3

)

Aboveground Ground contact Critical 

(UC3) (UC4A) structural

Preservative Percentages of active ingredients (UC4C)

CCA–C 19% CuO, 47% CrO , 34% As 0.25 (4.0) 0.40 (6.4) 0.60 (9.6)

ACQ–B and D 67% CuO, 33% DDAC 0.25 (4.0) 0.40 (6.4) 0.60 (9.6)

ACQ–C 67% CuO, 33% BAC 0.25 (4.0) 0.40 (6.4) 0.60 (9.6)

CA–B 96% Cu, 4% Azole 0.10 (1.7) 0.21 (3.3) 0.31 (5.0)

CBA–A 49% Cu, 2% Azole , 49% H BO 0.20 (3.3) 0.41 (6.5) 0.61 (9.8)

ACZA 50% CuO, 25% ZnO, 25% As 0.25 (4.0) 0.40 (6.4) 0.60 (9.6)

Creosote Creosote is the sole active ingredient. 8.0 (128) 10.0 (160) 12.0 (192)

Pentachlorophenol Pentachlorophenol is the sole active ingredient. 0.40 (6.4) 0.50 (8.0) 0.50 (8.0)

Copper naphthenate Copper naphthenate is the sole active ingredient. 0.04 (0.6) 0.06 (0.96) 0.075 (1.2)

Oxine copper 50% Cu-8 , 50% Nickel-2-ethylhexoate 0.02 (0.32) Not recommended

 RETENTION, PCF (kg/m

1

 Didecyldimethylammoniumcarbonate 

2

 Alkylbenzyldimethylammoniumchloride 

3

 Tebuconazole

Best Management Practices

The active ingredients of various waterborne wood 

preservatives (copper, chromium, arsenic, and zinc) are

water soluble in the treating solution, but resist leaching

when placed into the wood. This resistance to leaching 

is a result of chemical fixation reactions that render the 

toxic ingredients insoluble in water. The mechanism and

requirements for these fixation reactions differ, depending on the type of wood preservative. 

For each type of preservative, some reactions occur very

rapidly during pressure treatment, while others may take

days or even weeks, depending on storage and processing

after treatment. If the treated wood is placed in service 

before these fixation reactions have been completed, 

the initial release of preservative into the environment 

may be much greater than when the wood has been 

conditioned properly. 

4

 Expressed as retention of metallic copper

5

 Copper-8-quinolinolate

Concerns about inadequate fixation have led Canada and

European countries to develop standards or guidelines 

for fixing treated wood. Although oil-type preservatives

do not undergo fixation reactions, the amount of environmental release still depends on treatment practices. 

With oil-type preservatives, preservative that is bleeding

or oozing out of the treated wood is a particular concern.

This problem may be apparent immediately after treatment. Such members should not be used in bridges or 

other aquatic applications. In other cases, the problem 

may not become obvious until after the product has been

exposed to direct sunlight. This problem can be minimized by using treatment practices that remove excess 

preservative from the wood. 

BMP standards are being developed to ensure that treated

wood is produced in a way that will minimize environmental concerns and human health concerns (Pilon 

28
2002). The Western Wood Preservers Institute (WWPI) 

has developed guidelines for treated wood used in aquatic

environments (Western Wood Preservers Institute 1996).

Purchasers should specify and require assurance that 

the material they buy has been produced in compliance

with Best Management Practices for the Use of Treated

Wood in Aquatic Environments, USA version, revised 

January 1996, a publication of the Western Wood Preservers Institute and the Canadian Institute for Treated 

Wood. Publication of a new edition is scheduled for the

end of 2006. Although these practices have not yet been

adopted by the industry in areas outside the West Coast,

purchasers in other areas can require that these practices

be followed. Commercial wood treatment firms are 

responsible for meeting conditions that ensure fixation 

and minimize bleeding of preservatives, but persons 

buying treated wood should make sure that the firms 

have done so.

CCA—The risk of chemical exposure from wood treated

with CCA is minimized after chemical fixation reactions

lock the chemical in the wood. The treating solution 

contains hexavalent chromium, but the chromium 

reduces to the less toxic trivalent state within the wood.

This process of chromium reduction also is critical in 

fixing the arsenic and copper in the wood. Wood treated

with CCA should not be exposed to precipitation or 

other sources of environmental moisture until the fixation process is complete or nearly complete. The rate 

of fixation depends on temperature, taking only a few 

hours at 150 degrees Fahrenheit (66 degrees Celsius) but

weeks or even months at temperatures below 60 degrees

Fahrenheit (16 degrees Celsius). Some treatment facilities

use kilns, steam, or hot-water baths to accelerate fixation.

The BMP for CCA stipulates that the wood should be air

seasoned, kiln dried, steamed, or subjected to a hot-water

bath after treatment. It should be evaluated with the 

AWPA chromotropic acid test to determine whether 

Recommended Guidelines

fixation is complete (AWPA Standard A3–11, 2005). There

is some concern in the treatment industry that the 

chromotropic acid test may be overly conservative 

because it requires more than 99.5 percent of the chromium to be reduced to the trivalent form. However, 

the chromotropic acid test is the only standardized test 

available now.

ACZA and ACQ–B—The key to achieving stabilization

with these preservatives is to allow ammonia to volatilize.

This can be accomplished by air or kiln drying. The 

BMPs require a minimum of 3 weeks of air drying at 

temperatures higher than 60 degrees Fahrenheit (16 

degrees Celsius). The drying time can be reduced to 1 

week if the material is conditioned in the treatment 

cylinder. At lower temperatures, kiln drying or heat is 

required to complete fixation. There is no commonly 

used method to determine the degree of stabilization in

wood treated with ACZA or ACQ–B, although wood that

has been thoroughly dried is acceptable. If the wood has

a strong ammonia odor, fixation is not complete. 

ACQ–C, ACQ–D, and Copper Azole—Although 

these newer formulations are not in the current BMPs, 

they will be included in the 2006 revisions. Proper 

handling and conditioning of the wood after treatment 

helps minimize leaching and potential environmental 

impacts. Amine (and ammonia in some cases) keeps 

copper soluble in these treatment solutions. The mechanism of copper’s reaction in the wood is not completely

understood, but appears to be strongly influenced by 

time, temperature, and retention levels. 

Copper stabilization in the copper azole formulations is

extremely rapid (within 24 hours) at the lowest retention—0.10 pounds per cubic foot (6.4 kilograms per 

cubic meter)—but slows considerably at higher retentions

unless the material is heated to accelerate fixation. As a 

general rule, wood that has thoroughly dried after 

treatment is properly stabilized.

29
Recommended Guidelines

Pentachlorophenol, Creosote, and Copper 

Naphthenate—The BMPs for pentachlorophenol treatment stress thorough drying of the wood before treatment and the use of an empty-cell process. In an emptycell process, the air pressure is applied to the wood 

before the preservative is introduced to the treatment 

cylinder. After the pressure period, a final vacuum should

be used, as well as a final steaming or an expansion bath

similar to that described for the creosote treatments. 

For creosote, the BMPs stipulate use of an expansion 

bath and final steaming period at the end of the charge.

• Expansion Bath—Following the pressure period, the

creosote should be heated 10 to 20 degrees Fahrenheit

(–12 to –7 degrees Celsius) above the press temperatures for at least 1 hour. Creosote should be pumped 

back to storage and a minimum vacuum of 24 inches 

of mercury (–81kPa) should be applied for at least 2 

hours. 

• Steaming—After the pressure period and once the 

creosote has been pumped back to the storage tank, 

a vacuum of not less than 22 inches of mercury (–74 

kPa) shall be applied for at least 2 hours to recover 

excess preservative. Release the vacuum back to 

atmospheric pressure and steam for a 2-hour period 

for lumber and timbers and 3 hours for pilings. The 

maximum temperature during this process shall not 

exceed 240 degrees Fahrenheit (116 degrees Celsius).

Apply a second vacuum of not less than 22 inches of 

mercury (–74 kPa) for a minimum of 4 hours.

The BMPs for copper napthenate are similar to those for

creosote and pentachlorophenol. The recommended 

treatment practices for treatment in heavy oil include 

using an expansion bath and/or final steaming, similar 

to that described for creosote. When No. 2 fuel oil is 

used as the solvent, the BMPs recommend using a final 

vacuum for at least 1 hour.

Buyers can take steps to ensure that wood will be treated

according to the BMPs described above. Proper fixation

may take time. Material should be ordered well before 

it is needed so that the treatment firm can hold the wood

while it fixes. If buyers order wood in advance, they may

be able to store it under cover, allowing further drying 

and fixation. In general, allowing the material to air dry

before it is used is a good practice for ensuring fixation,

minimizing leaching, and reducing risk to construction 

personnel. With all preservatives, inspect the wood for 

surface residue. Wood with excess surface residue should

not be placed in service.

Use of a Treated Wood Product 

Site selection, construction, and handling practices can 

help to minimize the risks of using wood products 

treated with preservative.

Site Selection

1. Stay as far away from surface water as possible, because contaminants move less freely in soil than water.

2. Place trail crossings of sensitive ecosystems at their 

narrowest points (minimizing the use of treated wood

in sensitive areas).

3. Minimize the number of stream crossings (minimizing

the use of treated wood over water).

4. Review the guidelines for particular environmentally 

sensitive species.

Phaseout of CCA for Residential Uses

The EPA worked with pesticide manufacturers to voluntarily phase out CCA use for wood products around the

home and in children’s play areas. Effective December 

31, 2003, no wood treater or manufacturer may treat 

30
Recommended Guidelines

out of materials that are not treated with CCA. Forest 

Service applications where wood can be treated with 

CCA following the 2001 AWPA standards include:

• Highway bridges, (refer to C14, all members listed for

highway bridge construction are allowed).

• Piles for bridges, boardwalks, and viewing platforms 

(refer to C3). 

• Marine construction for saltwater use (refer to C18). 

• Round posts and poles used in building construction 

(refer to C23).

• Sawn timber, 5 by 5 inches (about 13 by 13 centimeters) and larger, used to support residential and commercial structures (refer to C24).

• Structural glue-laminated members (refer to C28). 

(Treated dimensional lumber for both glue- and naillaminated members may also be included under this 

standard.)

• Structural composite lumber (refer to C33).

Kiosk shingles and shakes (refer to C34), and round 

 posts and poles (refer to C23).

Figure 8—A bridge 

railing on the Trail 

of Blue Ice in the 

Chugach National 

Forest, AK.

• 

wood with CCA for residential uses (with certain exceptions). 

CCA has been used to pressure treat lumber since the 

1940s. Since the 1970s, the majority of the wood used in

outdoor residential settings has been treated with CCA. 

Although pressure-treated wood containing CCA is no 

longer being produced for most residential uses, including decks and playground equipment, structures and 

facilities may continue to be used even if they were 

constructed with wood treated with CCA before the 

voluntary phaseout. An oil-based stain can help lock the

CCA in place. See http://www.safe2play.org/assets/

docs/factsheet.pdf.

Allowable Uses of CCA-Treated Wood for Forest 

Service Projects

The EPA’s guidance for the use of CCA is the best source

of information on allowable uses. See the Web site: http://

www.epa.gov/oppad001/reregistration/cca/awpa_

table.htm.

Decking, railing (figure 8), and rail posts must be built 

31
Recommended Guidelines

• Signposts (refer to C14), wood for highway construction.

• Horse stables, hay storage buildings, and equipment 

storage (refer to C16).

• Corrals/fences (refer to C16), wood used on farms, 

such as fence posts, round, half-round, and quarterround fence rails. (Fence planks must be materials 

that were not treated with CCA.)

The list is partial; other uses may be allowed.

Construction, Handling, and Field 

Treatment 

Excessive exposure to inorganic arsenic and wood treated

with other preservatives may be hazardous to human 

health. Persons working with treated wood should take

a number of precautions:

• Saw, sand, and machine the treated 

wood outdoors. Wear a dust mask, 

goggles, and gloves. 

• Clean up all sawdust, scraps 

(figure 9), and other construction debris thoroughly 

and dispose of it in the 

trash (municipal solid 

waste). Do not compost 

or mulch sawdust or 

scraps of treated wood. 

• Do not burn treated wood. Toxic chemicals may be in

the smoke and ashes. 

• After working with the wood, wash all exposed areas

(especially the hands) thoroughly with soap and water

before eating, drinking, using the toilet, or using 

tobacco products. 

• Wash work clothes separately from other household 

clothing before wearing them again. 

These precautions will reduce your exposure from inhaling or ingesting sawdust, protect your eyes from flying

particles, and prevent exposure to toxic smoke and ash.

For more suggestions on avoiding unnecessary exposure

to treated wood, the EPA has identified some common 

sense tips. Before working with treated wood, always 

consult the Wood Preservative Science Council’s Inorganic Arsenical Pressure-Treated Wood consumer safety 

information sheet Web site (http://www.ccasafetyinfo.

com), or call 800–282–0600 to listen to the information 

or have the consumer information sheet faxed to you. 

Figure 9—A tub can be used to collect sawdust when drilling preservative-treated wood. 

Collecting debris during construction helps to minimize environmental impacts.

32
During construction, any holes or cuts that penetrate 

untreated wood should be treated with preservative. 

AWPA Standard M4 provides guidance for field treatment.

Typically, copper naphthenate is used. Be careful not to

drip or spill preservative where it will contaminate the 

environment. Whenever possible, treat the exposed 

surface before assembling the structure at a sensitive 

area. Do not place field-treated wood into water or soil 

before all excess preservative has been wiped off or has

soaked into the wood.

Disposing of Treated Wood 

Be careful to collect sawdust and other wood waste 

and remove it from the worksite. Treated wood is not 

listed as a hazardous waste under Federal law. It can be 

disposed of in any waste management facility authorized

under State and local law to manage such material.

Treated wood must not be burned in open fires or in 

stoves, fireplaces, or residential boilers, because the 

smoke and ashes may contain toxic chemicals. Treated 

wood waste from commercial and industrial sources 

Recommended Guidelines

(construction sites, for example) may be burned only 

in commercial or industrial incinerators or boilers in 

accordance with State and Federal regulations.

Generally, treated wood can be reused in a manner that

is consistent with its original intended end use. The 

industry publication Management of Used Treated 

Wood Products (http://www.wwpinstitute.org/main

pages/disposaloftreated.shtml) addresses some of the 

legal questions regarding the disposal and reuse of 

treated wood. For more information, please contact the

waste management agency in your State: http://www.

epa.gov/epaoswer/osw/Stateweb.htm.

State and local jurisdictions may regulate the 

use, reuse, and disposal of treated wood and 

treated wood construction waste. Users should 

check with State and local authorities for any 

special regulations relating to treated wood. 

Information about regulations in some areas 

also can be obtained by contacting the 

Western Wood Preservers Institute or the 

Treated Wood Council.

33
Material Safety Data Sheets 

Material safety data sheets (MSDS) are designed to 

provide workers and emergency personnel with 

information about the proper procedures for handling or working with a particular substance. These 

sheets include information about the materials, such as 

physical data (melting point, boiling point, flash point, 

and so forth), toxicity, health effects, first-aid treatment,

reactivity, storage, disposal, protective equipment, and 

spill or leak procedures. This information is particularly

important after a spill or other accident. The sheets 

can be requested from wood treatment firms or from 

chemical suppliers. A partial list of chemical suppliers 

and wood treatment firms is included in the section on 

Web sites.

34
Corrosiveness of Treatments 

Because the pressure-treated wood industry has been

phasing out CCA and using alternative chemicals for

treatment, the potential corrosiveness (figure 10) of

alternative wood preservatives needs to be considered. 

Hot-dipped galvanized fasteners meeting the ASTM A153

standard and connectors meeting the ASTM A653 Class 

G185 sheet-steel standard are recommended for protection against the effects of moisture when treated wood 

is used. 

Aluminum should not be used in direct contact with 

wood treated with copper-based preservatives. One 

fastener manufacturer, Simpson Strong-Tie, has conducted its own tests. Simpson found that some of the alternative treatments were slightly more corrosive than CCA. 

A report can be found at on Simpson’s Web site: http://

www.strongtie.com/productuse/corrosion.html.

The Forest Service Forest Products Laboratory is studying

the corrosiveness of alternative wood preservatives and

may provide some guidance. 

Figure 10—This metal plate used in a stress-laminated bridge constructed with preservative-treated wood shows the early signs of corrosion.—Photo courtesy of James Wacker

35
Web Sites 

Associations

American Wood-Preservers’ Association

Web site: http://www.awpa.com/

Forintek Canada Corp./Canadian Wood Council

Web site: http://www.durable-wood.com/

Southern Pine Council

Web site: http://www.southernpine.com/

Western Wood Preservers Institute

Web site: http://www.wwpinstitute.org/

Government Agencies

U.S. Environmental Protection Agency

Web site: http://www.epa.gov/oppad001/reregistration/ 

cca/

USDA Forest Service Forest Products Laboratory

Web site: http://www.fpl.fs.fed.us/

USDA Forest Service Missoula Technology and Development Center Facilities Toolbox Web site: http://www.

fs.fed.us/t-d/toolbox/haz/haz15.htm (Username: t-d, 

Password: t-d)

Preservative Manufacturers

Borax

Web site: http://www.borax.com/wood/

Chemical Specialties, Inc.

Web site: http://www.treatedwood.com

Osmose, Inc.

Web site: http://www.osmose.com/wood/usa/

Wolmanized Wood by Arch Wood Protection, Inc.

Web site: http://www.wolmanizedwood.com/

Others

Simpson Strong-Tie

Web site: http://www.strongtie.com/

36
Other Sources of Information 

Technical Southern Pressure Treaters Association

Stan Lebow P.O. Box 3219

USDA Forest Service Forest Products Laboratory Pineville, LA 71361

One Gifford Pinchot Dr. Phone: 318–619–8589

Madison, WI 53705–2398 Fax: 318–619–8589

Phone: 608–231–9411 Web site: http://www.spta.org/

Fax: 608–231–9508

E-mail: slebow@fs.fed.us Timber Piling Council

Web site: http://www.fpl.fs.fed.us/rwu4723 Phone: 800–410–2070

Fax 206–275–4755

Standards Web site: http://www.timberpilingcouncil.org/

American Wood-Preservers’ Association 

P.O. Box 361784 Treated Wood Council

Birmingham, AL 35236–1784 1111 19th St. NW., Ste. 800

Phone: 205–733–4077 Washington, DC 20036–3603

Fax: 205–733–4075 Phone: 202–463–4025

E-mail: email@awpa.com Fax: 202–463–2059

Web site: http://www.awpa.com/ E-mail: jeff_miller@treated-wood.org

Window & Door Manufacturers Association Western Wood Preservers Institute

1400 East Touhy Ave., Ste. 470 7017 NE. Hwy. 99, Ste. 108

Des Plaines, IL 60018 Vancouver, WA 98665

Phone: 847–299–5200 Phone: 360–693–9958 or 800–729–WOOD 

Fax: 847–299–1286 Fax: 360–693–9967

E-mail: admin@wdma.com Web site: http://www.wwpinstitute.org/

Web site: http://www.wdma.com/

Wood Preservative Science Council

Trade Associations P.O. Box 183

Suppliers of different types of treated wood can be Manakin-Sabot, VA 23103

found by contacting local lumberyards or the trade Phone: 804–749–8016 

associations that work with manufacturers of treated Fax: 804–749–8017

wood, including: Web site: http://www.woodpreservativescience.org/

37
References 

Brooks, Kenneth M. 2000. Assessment of the environmental effects associated with wooden bridges preserved

with creosote, pentachlorophenol, or chromated copper

arsenate. Res. Pap. FPL–RP–587. Madison, WI: U.S. Department of Agriculture Forest Service, Forest Products 

Laboratory. Available at: http://www.fpl.fs.fed.us/

documnts/fplrp/fplrp587.pdf

Falk, Bob; Williams, Sam. 1997. Details for a lasting deck.

In: Porches, decks, & outbuildings: the best of fine 

homebuilding. Newtown, CT: Taunton Press: 62–65. 

Available at: http://www.fpl.fs.fed.us/documnts/pdf

1997/falk97d.pdf

Forest Products Society. 1995. Selection and use of preservative-treated wood. Madison, WI: Forest Products 

Society.

Goyette, D.; Brooks, K.M. 1998. Creosote evaluation: 

phase II. Sooke Basin Study-baseline to 535 days post construction, 1995–1996. Rep. PR98–04. North Vancouver, 

BC, Canada: Environment Canada 568 p.

Highley, T.L. 1995. Comparative durability of untreated 

wood in use above ground. International Biodeterioration

& Biodegradation: 409–419. Available at: http://www.

fpl.fs.fed.us/documnts/pdf1995/highl95a.pdf

Lebow, Stan T.; Winandy, Jerrold; Bender, Donald. 2004.

Treated wood in transition: a look at CCA and the candidates to replace it. Wood Design Focus. 8 p. Available 

at: http://www.fpl.fs.fed.us/documnts/pdf2004/fpl_

2004_lebow005.pdf

Lebow, Stan T.; Tippie, Michael. 2001. Guide for minimizing the effect of preservative-treated wood on sensitive environments. Gen. Tech. Rep. FPL–GTR–122. 

Madison, WI: U.S. Department of Agriculture Forest 

Service, Forest Products Laboratory. Available at: http://

www.fpl.fs.fed.us/documnts/fplgtr/fplgtr122.pdf

Lebow, Stan T.; Halverson, Steven A.; Morrell, Jeffrey J.; 

Simonsen, John. 2000. Role of construction debris in 

release of copper, chromium, and arsenic from treated 

wood structures. Res. Pap. FPL–RP–584. Madison, WI: 

U.S. Department of Agriculture Forest Service, Forest 

Products Laboratory. Available at: http://www.fpl.fs.fed.

us/documnts/fplrp/fplrp584.pdf

Lebow, Stan T. 2000. Durability: what’s in pressure 

treated wood? Madison, WI: U.S. Department of Agriculture Forest Service, Forest Products Laboratory 

Techline. 3 p. Available at: http://www.fpl.fs.fed.us/

documnts/techline/whats-in-that-pressure-treatedwood.pdf

Lebow, Stan T. 1996. Leaching of wood preservative 

components and their mobility in the environment—

summary of pertinent literature. Gen. Tech. Rep. FPL–

GTR–93 U.S. Department of Agriculture Forest Service, 

Forest Products Laboratory. 36 p. Available at: http://

www.fpl.fs.fed.us/documnts/fplgtr/fplgtr93.pdf

Lebow, Stan T.; Makel, William J. 1995. Selection and 

use of preservative treated wood in Forest Service recreational structures. Tech. Rep. 9523–1203–SDTDC. 

San Dimas, CA: U.S. Department of Agriculture Forest 

Service, San Dimas Technology and Development 

Center. Available at: http://www.fs.fed.us/eng/pubs/

pdfimage/95231203.pdf

38
Mehta, P.K. 2001. Reducing the environmental impact of

concrete. Concrete International. 3(10): 61–66.

Pilon, John, ed. 2002. Best management practices for the

use of preservative-treated wood in aquatic environments

in Michigan. John Pilon, ed. Roscommon, MI: Michigan 

Department of Natural Resources. 26 p. For copies, 

contact the National Wood in Transportation Center at: 

http://www.fs.fed.us/na/wit/ or call the Huron Pines 

Resource Conservation and Development Area Council 

at 989–348–9319.

Ritter, Michael A.; Duwadi, Sheila Rimal. 1998. Research

accomplishments for wood transportation structures 

based on a national research needs assessment. Gen. 

Tech. Rep. FPL–GTR–105. Madison, WI: U.S. Department

of Agriculture Forest Service, Forest Products Laboratory.

30 p.

U.S. Department of Agriculture Forest Service, Forest 

Products Laboratory. 2000. Environmental impact of 

preservative-treated wood in a wetland boardwalk. Res.

Pap. FPL–RP–582. Madison, WI: U.S. Department of 

Agriculture Forest Service, Forest Products Laboratory.

Available at: http://www.fpl.fs.fed.us/documnts/fplrp/

fplrp582.pdf

References

U.S. Department of Agriculture Forest Service, Forest 

Products Laboratory. 1999. Wood handbook—wood as an

engineering material. U.S. Department of Agriculture 

Forest Service, Forest Products Laboratory. 463 p. 

Available at: http://www.fpl.fs.fed.us/documnts/

fplgtr/fplgtr113/fplgtr113.htm

Weis, P; Weis, J.S.; Greenburg, A.; Nosker, T.J. 1992. 

Toxicity of construction materials in the marine environment: a comparison of chromated-copper-arsenate treated

wood and recycled plastic. Archives of Environmental 

Contamination and Toxicology. 22: 99–106. 

Western Wood Preservers Institute. 1996. Best management practices for the use of treated wood in aquatic 

environments. Vancouver, WA: Western Wood Preservers

Institute. 35 p. Available at: http://www.wwpinstitute.

org/pdffiles/bmpsinaquatic.pdf

Western Wood Preservers Institute. [no date] Management of used treated wood products. Vancouver, WA: 

Western Wood Preservers Institute. 35 p. Web site: 

http://www.wwpinstitute.org/mainpages/

disposaloftreated.shtml

Western Wood Preservers Institute. [no date]. Guide to 

the characteristics, use and specifications of pressuretreated wood. Vancouver, WA: Western Wood Preservers

Institute. 13 p. Available at: http://www.wwpinstitute.

org/mainpages/guidetochar-use/center.html

39
Appendix A—EPA-Approved Consumer Information Sheets for Wood Pressure 

Treated With Pentachlorophenol or Creosote 

PENTACHLOROPHENOL 

Consumer Information

This wood has been preserved by pressure-treatment 

with an EPA-registered pesticide containing pentachlorophenol to protect it from insect attack and decay. Wood

treated with pentachlorophenol should be used only 

where such protection is important. Pentachlorophenol

penetrates deeply into and remains in the pressuretreated wood for a long time. Exposure to pentachlorophenol may present certain hazards. Therefore, the 

following precautions should be taken both when handling the treated wood and in determining where to use

and dispose of the treated wood.

Use Site Precautions

• Logs treated with pentachlorophenol should not be 

used for log homes.

• Wood treated with pentachlorophenol should not be 

used where it will be in frequent or prolonged contact

with bare skin (for example, chairs and other outdoor

furniture), unless an effective sealer has been applied.

• Pentachlorophenol-treated wood should not be used in

residential, industrial, or commercial interiors except 

for laminated beams or building components that are 

in ground contact and are subject to decay or insect 

infestation and where two coats of an appropriate 

sealer are applied. Sealers may be applied at the installation site. Urethane, shellac, latex epoxy enamel, and

varnish are acceptable sealers for pentachlorophenoltreated wood.

• Wood treated with pentachlorophenol should not be 

used in the interiors of farm buildings where there may

be direct contact with domestic animals or livestock 

that may crib (bite) or lick the wood.

• In interiors of farm buildings where domestic animals

or livestock are unlikely to crib (bite) or lick the wood,

pentachlorophenol-treated wood may be used for 

building components which are in ground contact 

and are subject to decay or insect infestation and 

where two coats of an appropriate sealer are applied. 

Sealers may be applied at the installation site.

• Do not use pentachlorophenol-treated wood for farrowing or brooding facilities.

• Do not use treated wood under circumstances where 

the preservative may become a component of food or 

animal feed. Examples of such sites would be structures

or containers for storing silage or food.

• Do not use treated wood for cutting boards or countertops.

• Only treated wood that is visibly clean and free of 

surface residue should be used for patios, decks, and 

walkways.

40
Appendix A—EPA-Approved Consumer Information Sheets for Wood Pressure Treated With Pentachlorophenol or Creosote

PENTACHLOROPHENOL

• Do not use treated wood for construction of those 

portions of beehives that may come into contact with

the honey.

• Pentachlorophenol-treated wood should not be used 

where it may come into direct or indirect contact 

with public drinking water, except for uses involving 

incidental contact such as docks and bridges.

• Do not use pentachlorophenol-treated wood where it 

may come into direct or indirect contact with drinking

water for domestic animals or livestock, except for 

uses involving incidental contact such as docks and 

bridges.

Handling Precautions

• Dispose of treated wood by ordinary trash collection 

or burial.

• Treated wood should not be burned in open fires or in

stoves, fireplaces, or residential boilers because toxic 

chemicals may be produced as part of the smoke and 

ashes. Treated wood from commercial or industrial 

use (e.g., construction sites) may be burned only in 

commercial or industrial incinerators or boilers rated 

at 20 million British Thermal Units/hour or greater 

heat input or its equivalent in accordance with State 

and Federal regulations.

• Avoid frequent or prolonged inhalation of sawdust from

treated wood. When sawing and machining treated 

wood, wear a dust mask. Whenever possible, these 

operations should be performed outdoors to avoid 

indoor accumulations of airborne sawdust from treated

wood.

• When power-sawing and machining, wear goggles to 

protect eyes from flying particles.

• Avoid frequent or prolonged skin contact with pentachlorophenol-treated wood.

• When handling the treated wood, wear long-sleeved 

shirts and long pants and use gloves impervious to the

chemicals (for example, gloves that are vinyl-coated).

• After working with the wood, and before eating, 

drinking, and using tobacco products, wash exposed 

areas thoroughly.

• If oily preservatives or sawdust accumulates on clothes,

launder before reuse. Wash work clothes separately 

from other household clothing.

41
Appendix A—EPA-Approved Consumer Information Sheets for Wood Pressure Treated With Pentachlorophenol or Creosote

CREOSOTE 

Consumer Information flooring. For such uses, two coats of an appropriate 

This wood has been preserved by pressure treatment sealer must be applied. Sealers may be applied at the 

with an EPA-registered pesticide containing creosote to installation site.

protect it from insect attack and decay. Wood treated • Wood treated with creosote should not be used in the

with creosote should be used only where such protec- interiors of farm buildings where there may be direct

tion is important. Creosote penetrates deeply into and contact with domestic animals or livestock that may 

remains in the pressure-treated wood for a long time. crib (bite) or lick the wood. In interiors of farm buildings where domestic animals or livestock are unlikely

Exposure to creosote may present certain hazards. There- to crib (bite) or lick the wood, creosote-treated wood

fore, the following precautions should be taken both may be used for building components that are in 

when handling the treated wood and in determining ground contact and are subject to decay or insect 

where to use the treated wood. infestation if two coats of an effective sealer are applied. Sealers may be applied at the installation site.

• Coal-tar pitch and coal-tar pitch emulsion are effective

Use Site Precautions sealers for creosote-treated wood-block flooring. 

• Wood treated with creosote should not be used where Urethane, epoxy, and shellac are acceptable sealers 

it will be in frequent or prolonged contact with bare for all creosote-treated wood. Do not use creosoteskin (for example, chairs and other outdoor furniture) treated wood for farrowing or brooding facilities.

unless an effective sealer has been applied. • Do not use treated wood under circumstances 

• Creosote-treated wood should not be used in residen- where the preservative may become a component of 

tial interiors. food or animal feed. Examples of such use would be 

• Creosote-treated wood in interiors of industrial structures or containers for storing silage or food.

buildings should be used only for industrial building • Do not use treated wood for cutting boards or councomponents that are in ground contact and are subject tertops.

to decay or insect infestation and for wood-block 

42
Appendix A—EPA-Approved Consumer Information Sheets for Wood Pressure Treated With Pentachlorophenol or Creosote

CREOSOTE 

• Only treated wood that is visibly clean and free of use (e.g., construction sites) may be burned only in 

surface residues should be used for patios, decks, and commercial or industrial incinerators or boilers in 

walkways. Do not use treated wood for construction accordance with State and Federal regulations.

of those portions of beehives that may come into • Avoid frequent or prolonged inhalation of sawdust 

contact with the honey. from treated wood. When sawing and machining 

• Creosote-treated wood should not be used where it treated wood, wear a dust mask. Whenever possible, 

may come into direct or indirect contact with public these operations should be performed outdoors to 

drinking water, except for uses involving incidental avoid indoor accumulations of airborne sawdust from

contact such as docks and bridges. treated wood.

• Do not use creosote-treated wood where it may come • When power-sawing and machining, wear goggles to 

into direct or indirect contact with drinking water for protect eyes from flying particles.

domestic animals or livestock, except for uses involving • Avoid frequent or prolonged skin contact with creoincidental contact such as docks and bridges. sote-treated wood; when handling the treated wood, 

wear long-sleeved shirts and long pants and use gloves

impervious to the chemicals (for example, gloves that

Handling Precautions are vinyl-coated).

• Dispose of treated wood by ordinary trash collection • After working with the wood and before eating, drinkor burial. ing, and using tobacco products, wash exposed areas 

• Treated wood should not be burned in open fires or in thoroughly.

stoves, fireplaces, or residential boilers, because toxic • If oily preservative or sawdust accumulates on clothes,

chemicals may be produced as part of the smoke and launder before reuse. Wash work clothes separately 

ashes. Treated wood from commercial or industrial from other household clothing.

43
Appendix B—Consumer Safety Information Sheet: Inorganic Arsenical PressureTreated Wood (Including CCA, ACA, and ACZA

For additional information, call toll-free: 800–282–0600,

or go to the Web site: http://www.ccasafetyinfo.com/.

Consumer Information

This wood has been preserved by pressure-treatment 

with an EPA-registered pesticide containing inorganic 

arsenic to protect it from insect attack and decay. Wood

treated with inorganic arsenic should be used only where

such protection is important.

Inorganic arsenic penetrates deeply into and remains 

in the pressure-treated wood for a long time. However, 

some chemical may migrate from treated wood into 

surrounding soil over time and may also be dislodged 

from the wood surface upon contact with skin. Exposure 

to inorganic arsenic may present certain hazards. Therefore, the following precautions should be taken both 

when handling the treated wood and in determining 

where to use or dispose of the treated wood.

Use Site Precautions

• All sawdust and construction debris should be cleaned

up and disposed of after construction.

• Do not use treated wood under circumstances where 

the preservative may become a component of food or 

animal feed. Examples of such sites would be use of 

mulch from recycled arsenic-treated wood, cutting 

boards, counter tops, animal bedding, and structures 

or containers for storing animal feed or human food.

• Only treated wood that is visibly clean and free of 

surface residue should be used for patios, decks, and 

walkways.

) 

• Do not use treated wood for construction of those 

portions of beehives, which may come into contact, 

with honey.

• Treated wood should not be used where it may come 

into direct or indirect contact with drinking water, 

except for uses involving incidental contact such as 

docks and bridges.

Handling Precautions

• Dispose of treated wood by ordinary trash collection.

Treated wood should not be burned in open fires or in

stoves, fireplaces, or residential boilers because toxic 

chemicals may be produced as part of the smoke and 

ashes. Treated wood from commercial or industrial 

use (e.g., construction sites) may be burned only in 

commercial or industrial incinerators or boilers in 

accordance with State and Federal regulations.

• Avoid frequent or prolonged inhalation of sawdust from

treated wood. When sawing, sanding and machining 

treated wood, wear a dust mask. Whenever possible, 

these operations should be performed outdoors to 

avoid indoor accumulations or airborne sawdust from

treated wood.

• When power-sawing and machining, wear goggles to 

protect eyes from flying particles.

• Wear gloves when working with the wood. After 

working with the wood, and before eating, drinking, 

toileting, and use of tobacco products, wash exposed 

areas thoroughly.

• Because preservatives or sawdust may accumulate on

clothes, they should be laundered before reuse. Wash

work clothes separately from other household clothing.

44
S

n

s

45

About the Authors

James “Scott” Groenier, professional engineer, began 

working for MTDC as a project leader in 2003. Scott 

earned a bachelor’s degree in civil and environmental 

engineering from the University of Wisconsin at Madison

and a master’s degree in civil engineering from Montana

State University. He worked for the Wisconsin and Illinois

State Departments of Transportation and with an engineering consulting firm before joining the Forest Service

in 1992. He worked as the east zone structural engineer

for the Eastern Region and as a civil engineer for the 

Ashley and Tongass National Forests before coming to 

MTDC.

Stan T. Lebow is a research scientist for the Durability 

and Wood Protection Research Unit at the Forest 

Service Forest Products Laboratory in Madison, WI. He 

conducts research in a range of areas involving wood 

protection, including the treatability and durability of 

new wood preservatives and the environmental impacts

of wood treated with preservatives. He also is active in 

the standards-setting process of the American WoodPreservers’ Association. Before joining the Forest Service

in 1993, he was the senior research scientist for the 

Department of Forest Products at Oregon State University,

where he received his Ph.D. in 1992.

Library Card

Groenier, James “Scott;” Lebow, Stan. 2006. Preservativetreated wood and alternative products in the Forest 

Service. Tech. Rep. 0677–2809–MTDC. Missoula, MT: U.S.

Department of Agriculture, Forest Service, Missoula 

Technology and Development Center. 44 p.

Provides an overview of:

• Wood preservatives

• Treatment processes used with wood preservatives

• Alternatives to treated wood

• Studies that have determined how much preservative 

leaches into the environment and its effects

• Guidelines for the use of preservatives and treated 

wood

Keywords: ACA, ACZA, best management practices, 

boardwalks, boric acid, CCA, construction, consumer 

information sheets, copper arsenate, copper chrome 

arsenates, copper naphthenate, creosote, corrosion, 

disposal, environmental impact, facilities, leaching, 

pentachlorophenol, pressure treatments, recreation, 

retention, standards, structures, trail bridges, wood 

chemistry, wood preservation, wood preservatives

For additional information about selection and use

of preservative-treated wood, contact Scott Groenier

at MTDC.

Phone: 406–329–4719

Fax: 406–329–3719

E-mail: jgroenier@fs.fed.us

Electronic copies of MTDC’s documents are available

on the Internet at: http://www.fs.fed.us/eng/t-d. php.

Forest Service and Bureau of Land Management 

employees can search a more complete collection 

of MTDC’s documents, videos, and CDs on their 

internal computer networks at: http://fsweb.mtdc.

wo.fs.fed.us/search/.

FOREST SERVICE TECHNOLOGY &

DEVELOPMENT

PROGRAM