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Alkaline Copper Quaternary (ACQ)

ACQ wood preservatives (types A, B, C, and D) are composed of copper oxide and a quaternary ammonia compound. The absence of chemicals like arsenic or chromium has made ACQ one of the most widely used residential wood preservatives. The EPA has registered ACQ wood treatments for use on lumber, fence posts, decking, landscape ties, utility poles, marine pilings, and other uses. For information and health risks associated with chemicals in ACQ, see the resources below.

For help selecting the proper type of treated wood for any setting, consider consulting the primary standard-setting body for treated wood, the American Wood Protection Association (AWPA).

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email us at npic@ace.orst.edu.

Additional Resources:

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Last updated January 22, 2021

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