How to Identify Types of Treated Lumber

From the 1980s through 2003, chromated copper arsenate (CCA) was the major type of chemical used to pressure-treat wood to increase its life when exposed to the weather. The phase-out of arsenic (AS-treated) wood began in January 2004 for residential use. ACZA or ammoniacal copper zinc arsenate--another current AS-treated wood--has a dark-brown color from the chemical reaction occurring during treatment, making it easy to identify. "Wood preservatives must meet two broad criteria: (1) They must provide the desired wood protection in the intended end use, and (2) they must do so without presenting unreasonable risks to people or the environment. Because wood preservatives are considered to be a type of pesticide, the U.S. Environmental Protection Agency (EPA) is responsible for their regulation," according to Stan Lebow of the U.S. Forest Service.

12-mL sample vial
1 dropper vial
8 mL ammonium molybdate reagent
1 mL stannous chloride reagent
1/3 tsp. shredded wood or sawdust from pressure-treated board

Instructions

- 1
  Examine lumber to locate the ink stamp on the end or near the bottom of the board. The stamp will have "AS-treated" if it has been pressure-treated with arsenic. Examples of lumber not treated with arsenic include the following, according to ccaresearch.org. An explanation of each item appears in parentheses.
  
  ACC - Acid Copper Chromate (safe chemicals)
  
  BB - Below Baseline (small amount of arsenic present; considered to be safe)
  
  BDL - Below Detection Level (unable to detect trace amount of arsenic)
  
  MDL - Minimal Detection Limit (very small trace amount of arsenic)
- 2
  Testing wooden structures requires purchasing a test kit or the individual chemicals to make your own test kit. The kit contains chemicals that will leave a blue stain if arsenic is present. To prepare the chemicals for staining the wood, remove the cap from the ammonium molybdate and draw up 8 mL of the chemical.
- 3
  Remove the cap from the second reagent and draw up 1mL stannous chloride. Pour the two chemicals into the empty 12-mL sample vial. Use the empty dropper vial to swirl and mix the two chemicals. Wait five minutes, then add 0.5 g or about 1/3 tsp. of sample shredded wood or sawdust from the structure you are testing. Only a small amount is needed and can be chipped from the underside of the structure, where it will not show.
- 4
  Stir the chemicals vigorously, then let stand. Reaction time should occur within 45 minutes. A blue color indicates an arsenate concentration above 2 mg/L, showing arsenic-treated wood. A clear, yellow, brown or beige color indicates the wood is unlikely to contain arsenic-treated wood.
- 5
  Read the tag or stamp on the end of each piece of lumber before purchase to learn key information about the type of pressure-treatment the lumber received. The tag or stamp should have the following information:
  
  Year treated
  
  Trade name of the wood product
  
  Intended use for the lumber (Example: "For above ground use.")
  
  Standard name of preservative used (Example: "Alkaline Copper")
  
  Name of third-party inspection agency
  
  AWPA use category (A shorthand code for intended use issued by the American Wood Protection Association; this code duplicates the intended use listed above)
  
  Retention of preservative (This number appears below the standard name of preservative and indicates the minimum amount of preservative in the wood; expressed in pounds per cubic foot)
  
  Name and location of treating company

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