A chemical NOT used as a preservative for treating wood fencing is:

• A. Calcium chloride
• B. Pentachlorophenal
• C. Ammoniacal copper zinc arsenate
• D. Creosote

Answer: (A)

Wood preservatives are chosen for their ability to penetrate wood and defend it against decay fungi and wood-boring insects over time. Creosote, pentachlorophenol, and ammoniacal copper zinc arsenate are classic preservatives because they provide durable toxicity to organisms that threaten wood.

Calcium chloride, however, is a highly soluble salt used mainly as a de-icer and moisture-control additive. It does not offer lasting protection against decay or insects and it tends to leach out of wood, providing little to no long-term preservative effect. That’s why calcium chloride is not used to treat wood fencing.