Wood preservation facilities, general recommendations: chapter A-2

2. Physical and Chemical Properties

Before using a wood preservative, the following characterization should be identified and understood.

2.1 General Properties

Physical and chemical properties of the wood preservative should be gathered and documented and stored on -site. This information can usually be found on the pesticide label and material safety data sheets (MSDS), which are provided by the manufacturers (3). Electronic copies of pesticide label are also available from the Health Canada website

Table 2 provides the suggested format to document the physical and chemical properties (if applicable) of the wood preservatives.

2.2 Stabilization and Fixation of the Preservative

In order to minimize leaching of the preservatives to the environment, treated wood with water-borne preservatives undergoes the process of stabilization or fixation. Throughout the 2013 Technical Recommendations Document (TRD) for the design and operation of wood preservation facilities, stabilization requirements are provided for most wood preservatives, and fixation requirements are provided for Chromated Copper Arsenate, (CCA) Type C (in Chapter B of the 2013 TRD).

Fixation refers to a physical or chemical process whereby a wood preservative system is rendered leach resistant in both water and soil applications in such a way that the active ingredient or ingredients maintain fungal/insecticidal efficacy (2).

Stabilization is a similar to fixation; however, there is no chemical reaction involved in the process to fix the mobility of the preservative in the wood. Following a specific period of dripping time after treatment, a simple drip-free visual verification is usually involved to check the stabilization of the treated wood. The minimum period of dripping is generally 48 hours under adequate conditions. Factors that may influence the duration of the stabilization/fixation process include concentration and formulation of the preservative, air flow, humidity, wood species involved, temperature and moisture content.

Prior to application, the users should have a good understanding and maintain documentation of the stabilization/fixation process, its requirements, the quality control method, the potential airborne emissions and the appropriate precautions to minimize risk of exposure.

To improve and gain better understanding of the stabilization/fixation process, a log book should be maintained to document the air flow, temperature and humidity of the accelerated fixation chamber or stabilization kiln.