Different applications impose different hazards on wood, and require different amounts of preservative for protection. These amounts are called “retention levels,” referring to the amount of preservative retained in the wood after treatment. Furthermore, each preservative has its individual retention level for these applications. Be sure to obtain wood treated for the application you have in mind. The intended use is identified on the tag stapled to each piece of lumber.
AWPA Standards
Code Preservative Name UC1, 2 UC3B UC4A UC4B
ACC Acid Copper Chromate 0.25 0.25 0.50 ---
ACQ Alkaline Copper Quaternary (Type B or C) 0.25 0.25 0.40 0.60
ACQ Alkaline Copper Quaternary (Type A or D) 0.15 0.15 0.40 0.60
ACZA Ammoniacal Copper Zinc Arsenate 0.25 0.25 0.40 0.60
CA-B Copper Azole, Type B 0.10 0.10 0.21 0.31
CA-C Copper Azole, Type C 0.060 0.060 0.15 0.31
CuN-W Waterborne Copper Naphthenate 0.070 0.070 0.11 ---
CX-A Copper HDO 0.206 0.206 --- ---
EL2 DCOI-Imidicloprid-Stabilizer 0.019 0.019 --- ---
PTI Propiconazole-Tebuconazole-Imidicloprid 0.013 0.018 --- ---
PTI PTI plus Stabilizer 0.013 0.013 --- ---
SBX Inorganic Boron (Formosan termites) 0.28 --- --- ---
SBX Inorganic Boron (non-Formosan termites) 0.17 --- --- ---
Use Category Brief Description
UC1 Interior Dry
UC2 Interior Damp
UC3A Exterior Above Ground, Coated with Rapid Water Runoff
UC3B Exterior Above Ground, Uncoated or Poor Water Runoff
UC4A Ground Contact, General Use
UC4B Ground Contact, Heavy Duty
UC4C Ground Contact, Extreme Duty
UC5A Marine Use, Northern Waters (Salt or Brackish Water)
UC5B Marine Use, Central Waters (Salt or Brackish Water)
UC5C Marine Use, Southern Waters (Salt or Brackish Water)
UCFA Interior Above Ground Fire Protection
UCFB Exterior Above Ground Fire Protection
