What is incombustible wood? Overall incombustible certificate

Most people might have heard about incombustible wood but do most people really know what kind of product are they?
In addition,when the law are involved there are people who might taught the deeper your search goes the harder it gets.
This page will explain about incombustible wood easily.

Incombustible wood is

Due to Ministry of Land, Infrastructure, Transport and Tourism, material that fit the criteria below are called「Fire protecting material」
Enforcement Ordinance of Construction Standard Law article 108-2

  • No.1 Nonflammable object
  • No.2 Do not deform melt crack or cause other damage on fire prevention
  • No.3 Do not generate harmful gas or smoke on evacuation

This fireproof wood is certified by Ministry of Land, Infrastructure, Transport and Tourism standard and generally called 「Incombustible wood」

Fire protecting material like incombustible wood have the performance standard.

Fire protecting materials (include incombustible wood) are classified into 3 categories
(Performance will be evaluated by how many minutes the criteria are met after start heating with the test machine)

  • Incombustible              After start heating 20 minutes
  • After start heating       After start heating 10 minutes
  • Quasi-incombustible   After start heating   5 minutes

In the other word, Incombustible wood existed in incombustible, semi-incombustible and quasi-incombustible

Why incombustible wood are hard to burn

Incombustible wood are mainly maded by immerse (soak) natural wood into Boric acid and Phosphoric acid.
These chemical will create carbonized film on wood surface then help them difficult to burn.

Website that public incombustible number certificate overview.

Minister cerificate number and overall are publicised on MILT website
Incombustible wood are in the middle of the page on「Fire protecting material/ Fire protecting equipment」correspond with「Incombustible wood, Semi-incombustible, Quasi-incombustible 」


Incombustible wood is wood that was treated with chemical.
The outstanding characters are the following, will not burn deform or generate toxic gas in the period of normal fire burning. They are classified by fire-resistance period in 3 levels as 「Incombustible(20 minute)」「Semi-incombustible (10 minute)」「Quasi-incombustible (5 minute)」

Please check the below pages

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