H1

H1 is a lower-level treatment used for timber that will be in a dry, indoor environment. The main goal of H1 treatment is to protect the timber from [[Lyctid borers[[ (also known as powder post beetles) and, in some cases, other insects.<ref>https://www.epa.nsw.gov.au/Your-environment/Household-building-and-renovation/Treated-timber/timber-treatments/boron-based-treated-timber#:~:text=large%20environmental%20threat.-,Boron%2Dbased%20treated%20timber,borer%20(Powder%20post%20borer).</ref>

The primary chemical used for H1 treatment is a boron compound, specifically disodium octaborate tetrahydrate.<ref>https://www.epa.nsw.gov.au/Your-environment/Household-building-and-renovation/Treated-timber/timber-treatments/boron-based-treated-timber#:~:text=The%20active%20ingredient%20of%20boron,of%20the%20Tropic%20of%20Capricorn.</ref>

Here's why boron is the ideal chemical for H1:

Low Hazard: Boron compounds are considered low in toxicity to mammals and are less of an environmental concern compared to the chemicals used in higher hazard level treatments (like the arsenic in CCA). This makes it suitable for indoor applications where human contact is more likely.

Effective Against Borers: Boron is highly effective at killing the insects and larvae of Lyctid borers, which are the main threat to susceptible hardwoods used in indoor applications.

Water-Based: Boron treatments are typically water-based. The timber is often soaked or pressure-treated with the solution, and the boron then diffuses into the wood.

Not Leaching-Resistant: A key characteristic of boron is that it can leach out of the timber if it gets wet. This is why H1-treated timber is only for indoor, above-ground applications where it is completely protected from moisture and weather. If it were to be used outdoors, rain would wash the preservative away, rendering the treatment ineffective.

In some contexts, especially in Australia, H2 treatments which also use boron (but with a higher retention level and sometimes in combination with other chemicals) are often used as a standard for internal framing. However, for H1, boron is the core chemical used to protect against borers.