Light Organic Solvent Preservatives (LOSP) : Safe Handling & Storage


Light Organic Solvent-borne Preservatives (LOSPs) are preservatives that contain combinations of fungicides and insecticides for timbers used in internal and external situations. All of these preservative components are incorporated in a solvent carrier such as white spirit.

This information sheet is designed to inform treaters, prenailers, merchants and builders of correct procedures for handling and storing LOSP treated timber.


LOSP treated timber may retain some of the solvent used in the treatment process for a period of time after treatment. The following precautions should be taken to minimise any potential health effects to users.

  • LOSP treated timber should be stored in a well ventilated, under cover area with any protective wrapping removed.
  • Where possible packs should be opened a day or two before use to allow any residual solvent vapours in the inner boards to evaporate.


Users of any timber product, whether treated or not, should take some simple precautions to limit their exposure to wood dust when working with timber.

Some people may experience temporary skin irritation, headaches or light headedness when using LOSP treated timber. These undesirable effects are more likely if the timber is not solvent dry.

The following precautions should be taken when handling LOSP treated timber:

  • Wear gloves and long sleeves for protection against splinters and cuts during handling. Treatment plant operators should wear solvent resistant gloves when handling timber that is still damp from treatment. Application of a chemical resistant barrier cream to exposed areas, particularly wrists and forearms, is strongly recommended.
  • Wear protective glasses and a filter mask when sawing, sanding or machining treated timber.
  • Working with solvent damp timber is inadvisable, however, an impervious work apron must be used to protect clothing if direct contact proves unavoidable.
  • If LOSP preservative or treated sawdust accumulates on clothes, wash separately before reuse.
  • Always wash hands after handling LOSP treated timber, especially before eating.
  • Do not transport LOSP treated timber in an enclosed environment.
  • If undesirable effects occur cease handling or using the material and review your personal protection measures.


  • Always ensure LOSP treated timber is stored in a well ventilated space.
  • Merchants and prenailers should remove wrapping off delivered material as soon as convenient to assist in the dissipation of solvent fumes.
  • Stored LOSP treated timber should not be kept in a confined area. Store only in areas that have double ventilated openings or an extraction system.

Flash off times

Freshly LOSP treated timber should be stored for an adequate time to permit "flash off" of solvents prior to transport off site.

The Best Practice Guideline for Timber Preservatives states that LOSP treated timber should be held unwrapped in fillet for four (4) days after treatment. Alternative means of achieving solvent dissipation may be used to achieve the same level. This will aid on the dissipation of solvents from freshly treated timber.


  • Large amounts of LOSP treated timber waste may require special approval from your local Authority.
  • For normal domestic and trade users, dispose of waste through normal waste collection and disposal services.
  • LOSP treated timber shall not be burned in open fires, stoves, fireplaces or any confined spaces.

Reputable LOSP treaters are licensed to use the WOODmark® brand. The WOODmark® brand signifies that timber has been treated to the requirements of the New Zealand Standard NZS3640:2003 and that the treater follows the quality assurance procedures laid down in the New Zealand Timber Preservation Council's Timber Preservation Quality Manual.

Make sure you buy and use only WOODmark® treated timber and wood products.