Pressure-treated wood is commonly encountered during building demolition, infrastructure rehabilitation, utility pole removal, and waste characterization projects. Correct identification is important for worker protection, waste segregation, recycling decisions, and environmental compliance.
Field personnel often rely on visual indicators such as green or brown coloration, treatment stamps, or mechanical incising marks to identify treated wood. While these observations can be useful, they are not always reliable. Weathering, ultraviolet exposure, dirt accumulation, biological growth, and surface coatings can alter the appearance of wood to the point where treated and untreated materials become visually indistinguishable.
For designated substance assessments and demolition projects, laboratory analysis can provide objective evidence regarding the presence or absence of wood preservatives.
Types of Pressure-Treated Wood
Wood preservatives generally fall into two broad categories: water-based systems and oil-based systems.
Water-Based Preservatives
Water-based preservatives are widely used to protect wood from fungal decay and insect attack. These formulations typically contain copper as the primary biocidal component and may also contain chromium, arsenic, boron, or organic co-biocides depending on the treatment system and the age of the material.
Examples include:
- Chromated Copper Arsenate (CCA)
- Alkaline Copper Quaternary (ACQ)
- Copper Azole (CA)
- Micronized Copper formulations
Although the use of arsenic-containing preservatives has been significantly reduced for residential applications, CCA-treated wood remains common in older structures and continues to be used in certain industrial applications.
Oil-Based Preservatives
Oil-based preservatives are typically associated with industrial wood products such as:
- Utility poles
- Railway ties
- Marine pilings
- Bridge timbers
- Industrial foundation systems
Common oil-based preservatives include:
- Pentachlorophenol (PCP)
- Creosote
These preservatives are highly effective for long-term outdoor service and can remain detectable decades after treatment.
Challenges of Visual Identification
Visual examination alone may not be sufficient to distinguish treated from untreated wood.
Common limitations include:
- Weathered wood often loses its original treatment colour.
- Surface coatings may conceal treatment characteristics.
- Dirt and biological growth can obscure identifying features.
- Older lumber may no longer display treatment stamps.
- Incising marks are not present on all treated products.
As a result, laboratory testing may be required when treatment status affects waste classification, demolition planning, recycling options, or environmental reporting.
Laboratory Screening for Water-Based Preservatives
Elemental Analysis by X-Ray Fluorescence (XRF)
LCS Laboratory uses X-ray fluorescence (XRF) analysis to screen wood samples for elevated copper concentrations associated with preservative treatment.
Copper is the principal active ingredient in most modern water-based wood preservatives. Treated wood typically contains copper concentrations substantially higher than those found in natural wood.
Typical copper concentrations are shown below:
| Material | Typical Copper Concentration |
| Untreated wood | Less than 10 mg/kg |
| Elevated background or minor contamination | 10–50 mg/kg |
| Possible anthropogenic contamination | Greater than 100 mg/kg |
| Copper-based preservative treatment | Frequently greater than 1,000 mg/kg |
For demolition and waste characterization projects, copper concentrations above approximately 100–200 mg/kg may warrant further investigation, while concentrations exceeding 1,000 mg/kg are generally consistent with copper-based preservative treatment.
Elemental screening can also identify elevated arsenic and chromium concentrations associated with older CCA-treated wood.
Laboratory Screening for Oil-Based Preservatives
Analysis for Pentachlorophenol and Creosote
Industrial timbers treated with pentachlorophenol or creosote require a different analytical approach because these preservatives are organic compounds rather than metals.
Wood samples are extracted and analyzed using high-temperature gas chromatography to determine the presence of oil-based preservatives.
Typical pentachlorophenol concentrations are shown below:
| Material | Typical PCP Concentration |
| Untreated natural wood | Less than 0.1–5 mg/kg |
| Wood affected by environmental contamination | 1–100 mg/kg |
| Pressure-treated utility pole wood | 5,000–25,000 mg/kg |
| Surface shavings from heavily treated poles | Up to 50,000 mg/kg or higher |
For practical interpretation:
- Concentrations below 100 mg/kg are generally consistent with environmental contamination rather than preservative treatment.
- Concentrations above 1,000 mg/kg are strongly indicative of pressure-treatment.
- Utility poles and industrial timbers commonly contain PCP concentrations in the range of 10,000–30,000 mg/kg.
These concentrations often remain detectable after decades of outdoor service.
Applications for Designated Substance and Demolition Assessments
Laboratory identification of pressure-treated wood may assist with:
- Designated substance assessments
- Hazardous materials surveys
- Demolition planning
- Utility pole characterization
- Railway tie investigations
- Waste acceptance testing
- Recycling and reuse evaluations
- Environmental due diligence projects
- Construction and demolition waste management programs
Analytical results provide objective documentation that can support waste classification decisions and demonstrate due diligence during project planning.
Sample Collection
Wood samples for analysis can typically be collected by removing a small section of material from the structure or waste stream of interest.
For best results:
- Collect a representative piece of wood.
- Place the sample in a clean sealable plastic bag.
- Label the sample with the project location and sample identification number.
- Submit the sample to the laboratory for analysis.
Where multiple wood types are present, separate samples should be collected from each material category. To discuss your project, please contact LCS Laboratory Inc.
